FL_Medic Posted July 31, 2006 Share Posted July 31, 2006 Home | Specialties | Resource Centers | Learning Centers | CME | Contributor Recruitment July 30, 2006 Articles Images CME Advanced Search Consumer Health Link to this site You are in: eMedicine Specialties > Pediatrics > Nephrology Acute Tubular Necrosis Last Updated: July 28, 2006 Rate this Article Email to a Colleague Get CME/CE for article Synonyms and related keywords: acute tubular necrosis, ATN, acute renal failure, ARF, acute intrinsic renal failure, acute vasomotor nephropathy, oliguria, anuria, ischemic ATN, nephrotoxic ATN AUTHOR INFORMATION Section 1 of 10 Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Bibliography Author: Prasad Devarajan, MD, Louise M Williams Endowed Chair, Professor of Pediatrics & Developmental Biology, Director of Nephrology and Hypertension, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati Coauthor(s): Robert Woroniecki, MD, Assistant Professor, Department of Pediatrics, Section of Pediatric Nephrology, Albert Einstein College of Medicine, Children's Hospital of Montefiore Prasad Devarajan, MD, is a member of the following medical societies: American Academy of Pediatrics, American Heart Association, American Society of Nephrology, American Society of Pediatric Nephrology, National Kidney Foundation, and Society for Pediatric Research Editor(s): Richard Neiberger, MD, PhD, Director of Pediatric Renal Stone Disease Clinic, Associate Professor, Department of Pediatrics, Division of Nephrology, University of Florida College of Medicine and Shands Hospital; Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine.com, Inc; Adrian Spitzer, MD, Professor, Department of Pediatrics, Albert Einstein College of Medicine; Director of NIH Training Program, Children's Hospital at Montefiore Medical Center; Howard Trachtman, MD, Program Director, Pediatrics Research, Schneider Children's Hospital, Professor, Department of Pediatrics, Division of Nephrology, Albert Einstein College of Medicine; and Craig B Langman, MD, Professor, Department of Pediatrics, Northwestern University School of Medicine; Head, Division of Kidney Diseases, Children's Memorial Hospital of Chicago Disclosure INTRODUCTION Section 2 of 10 Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Bibliography Background: Acute tubular necrosis (ATN) is characterized pathologically by varying degrees of tubule cell damage and by cell death usually resulting from prolonged renal ischemia, nephrotoxins, or sepsis. ATN is characterized clinically by acute renal failure (ARF), which is defined as a rapid (hours to days) decline in the glomerular filtration rate (GFR) that leads to retention of waste products such as BUN and creatinine. The various etiologies of ARF can be grouped into 3 broad categories: prerenal, intrinsic renal, and postrenal. Prerenal ARF (55% of ARF) is a functional response of structurally normal kidneys to hypoperfusion, whereas postrenal ARF (<5% of ARF) is a consequence of mechanical or functional obstruction to urine flow. Intrinsic ARF (40% of ARF) is the result of structural damage to the renal tubules, glomeruli, interstitium, or renal vasculature. Most intrinsic ARF cases are associated with ATN from prolonged ischemia or toxic injury, and the terms ischemic and nephrotoxic ATN are frequently used synonymously with ischemic or nephrotoxic ARF. The focus of this article is ischemic and nephrotoxic ATN. Other important causes of intrinsic ARF in children, such as hemolytic-uremic syndrome (HUS) and immunologic glomerular diseases, are not discussed. The clinical course of ATN may be divided into initiation, maintenance, and recovery phases. The initiation phase corresponds to the period of exposure to ischemia or nephrotoxins. Renal tubule cell damage begins to evolve (but is not yet established) during this phase. GFR starts to fall, and urine output decreases. During the maintenance phase, renal tubule injury is established, the GFR stabilizes at the level well below normal, and the urine output is low or absent. Although oliguria (or anuria) is one of the clinical landmarks of ATN, it is absent in a minority of patients with so-called nonoliguric ATN. ARF due to nephrotoxins is typically nonoliguric. The second phase of ATN lasts usually for 1-2 weeks but may extend to a few months. The recovery phase of ATN is characterized by polyuria and gradual normalization of GFR; however, when ATN occurs (as it often does) in the context of multiorgan dysfunction, regeneration of renal tissue may be severely impaired and renal function may not return. Morbidity and mortality in such situations remains dismally high in spite of significant scientific and technological advances. Pathophysiology: The current understanding of the pathophysiology of ATN is the result of intensive scientific studies performed over many decades. Despite the nomenclature, frank necrosis of tubule cells is relatively inconspicuous in ischemic ATN, whereas it can be more extensive in heavy metal-induced nephrotoxic ATN. The typical findings in humans include (1) patchy loss of tubular epithelial cells with resultant gaps and exposure of denuded basement membrane; (2) diffuse effacement and loss of proximal tubule cell brush border; (3) patchy necrosis, most typically in the outer medulla where the straight (S3) segment of the proximal tubule and the medullary thick ascending limb (mTAL) of Henle loop; (4) tubular dilatation and intraluminal casts in the distal nephron segments; and (5) evidence of cellular regeneration. Regenerating cells are often detected in biopsies together with freshly damaged cells, suggesting the occurrence of multiple cycles of injury and repair. Alterations in renal hemodynamics Decreases in effective intravascular volume, in cardiac output, or in renal blood flow trigger compensatory mechanisms that result in afferent arteriolar dilatation via myogenic responses, tubuloglomerular feedback, and prostaglandins), efferent arteriolar constriction (via angiotensin II), and enhanced tubular salt and water reabsorption (stimulated by angiotensin II and sympathetic nervous system). When the renal hypoperfusion is prolonged, a shift from compensation to decompensation occurs. Excessive stimulation of the sympathetic nervous system and the renin-angiotensin system causes profound renal vasoconstriction that eventually results in tubular damage. Iatrogenic interference with renal compensation by administration of vasoconstrictors (cyclosporine or tacrolimus), inhibitors of prostaglandin synthase (nonsteroidal anti-inflammatory drugs [NSAIDs]), or inhibitors of the renin-angiotensin system, such as ACE inhibitors or angiotensin receptor antagonists, can precipitate ATN in individuals with reduced renal perfusion. Severe renal vasoconstriction (25-50% of normal) has been documented in experimental and clinical ARF and has been considered in the past as a dominant causative factor. That explains the name of vasomotor nephropathy given to this condition; however, reduction in total renal blood flow alone does not appear to account for the profound reduction in GFR since improvement of renal blood flow by volume expansion or administration of vasodilators does not correct GFR. Recent studies suggest that persistent abnormalities in intrarenal blood flow involving the outer medullary region may contribute to the reduction in GFR. The outer medulla is relatively hypoxic even under normal conditions, with a partial pressure of oxygen being 10-20 mm Hg (compared to 50-60 mm Hg in the cortex), rendering the tubular segments in this region (namely the S3 segment of the proximal tubule and the mTAL) highly susceptible to ischemia. For reasons that are incompletely understood, hypoxia and vasoconstriction persist in the outer medullary region even after total renal blood flow returns to normal, resulting in further tubular injury. Mediators of both the renal vasoconstriction and the persistent reduction in medullary blood flow most likely include endothelin-1, angiotensin II, prostaglandins, adenosine, and nitric oxide. Elevated levels of endothelin-1, a potent renal vasoconstrictor, have been demonstrated in patients with ARF of various etiologies, and endothelin receptor antagonists have been shown to ameliorate experimental ARF. A role for angiotensin II, another potent renal vasoconstrictor, has been proposed because hyperplasia of the juxtaglomerular apparatus with increased renin granule content and increased plasma renin activity have been demonstrated in patients with ARF. However, inhibition of angiotensin II does not diminish the extent of renal injury in experimental ARF and may precipitate ARF in patients with diminished effective blood volume. This makes the role of angiotensin II in human ATN uncertain. Adenosine has been incriminated as a renal vasoconstrictor in contrast nephropathy. Pretreatment with adenosine receptor antagonists, such as theophylline, can blunt the abrupt reduction in GFR induced by contrast agents, but these agents are ineffective once ATN is established. A deficiency of renal vasodilators, such as endothelium-derived nitric oxide and prostaglandins, may also play a role in the initiation of ATN, but no evidence exists that administration of either mediator alters the course of established ATN. The inability of nitric oxide donors, such as nitroprusside, to improve the course of ischemic ARF may be related to the paradoxical toxic effects of nitric oxide on proximal tubule cells via generation of reactive oxygen species. Although a deficiency of vasodilatory atrial natriuretic peptide (ANP) has not been demonstrated in ATN, ANP has been reported to increase renal blood flow, GFR, natriuresis and diuresis in experimental ischemic and toxic ARF, when infused shortly after the onset of renal ischemia. In human trials, ANP offered no benefit when administered to critically ill adults with ATN but did appear to improve the overall survival in a subset of patients with oliguric ATN. Alterations in tubule function The tubular segments located within the medullary region (S3 segment of proximal tubule and mTAL) are particularly vulnerable to ischemia because the oxygen tension in this region is low even under normal conditions, and both segments have a high rate of oxygen consumption. The active transport of sodium that occurs at this level depends on oxidative phosphorylation for energy. Consequently, these tubular segments are extremely susceptible to ischemia and to those nephrotoxins that disrupt energy production or mitochondrial function. Tubular obstruction also contributes to the reduction in GFR. Recent studies revealed that tubular obstruction is produced predominantly by the exfoliation of viable (rather than necrotic) tubule cells, leaving behind denuded areas of the basement membrane. Another factor leading to the reduction of GFR is the combination of exposed basement membrane and the loss of tight junctions in the attached proximal tubule cells that result in tubular back leak of a variety of substances, including creatinine and urea. The back leak renders these substances unsuitable for the estimation of GFR. Activation of the tubuloglomerular feedback system may also contribute to the reduction in GFR. The increased delivery of sodium chloride to the distal nephron segments, specifically the macula densa, due to cellular abnormalities in the ischemic proximal tubule would be expected to induce afferent arteriolar constriction via A1 adenosine receptor (A1AR) activation and thereby decrease GFR. However, recent animal studies have shown that a knockout of the A1AR resulted in a paradoxical worsening of ischemic renal injury, and exogenous activation of A1AR was protective. Thus, tubuloglomerular feedback activation following ischemic injury may indeed represent a beneficial phenomenon that limits wasteful delivery of ions and solutes to the damaged proximal tubules, thereby reducing the demand for ATP-dependent reabsorptive processes. Any salutary effect of exogenous A1AR activation in human ATN remains to be determined. Alterations in tubule cell metabolism Adenosine triphosphate (ATP) depletion plays a pivotal role in renal cell injury. In general, cellular ATP is produced by mitochondrial oxidative phosphorylation and by glycolysis in the endoplasmic reticulum. Proximal tubule cells are dependent predominantly on mitochondria for ATP synthesis, rendering them especially susceptible to oxygen deprivation in ischemic ATN and to nephrotoxins that cause mitochondrial damage. Oxygen deprivation results in rapid catabolism of ATP to adenosine diphosphate (ADP) and adenosine monophosphate (AMP). Restoration of oxygen allows for rapid rephosphorylation of these adenine nucleotides to ATP; however, prolonged ischemia results in further catabolism of adenine nucleotides to adenosine and hypoxanthine, which can diffuse passively out of the cell and deplete the adenine nucleotide pool for ATP synthesis. Prolonged cellular ATP depletion initiates a sequence of events including inhibition of ATP-dependent transport mechanisms, activation of proteases, and cytoskeletal alterations. The importance of ATP depletion has been underscored by the demonstration in animal models that provision of exogenous adenine nucleotides partially ameliorates cellular injury following ischemia. Reactive oxygen species (ROS), such as hydroxyl radical, peroxynitrite, and hypochlorous acid, are generated from several sources during reperfusion of ischemic kidneys. The hydroxyl radical can be formed from superoxide and hydrogen peroxide, which under normal circumstances are produced continually by tubule cells. The final conversion of hydrogen peroxide to hydroxyl radical requires ferrous iron. Naturally occurring antioxidants, such as superoxide dismutase, catalyze the conversion of superoxide to hydrogen peroxide, which, in turn, is converted to water by catalase or glutathione peroxidase, thereby conferring cryoprotection. Prolonged ischemia results in the catabolism of cellular ATP to hypoxanthine, and the concomitant calcium-dependent activation of xanthine oxidase. During reperfusion, xanthine oxidase uses molecular oxygen as an electron receptor while converting hypoxanthine to xanthine, thereby generating excessive superoxide that can overwhelm the tubule cell's defenses against hydroxyl radical production. Other sources of ROS include mitochondria that are damaged during ischemia-reperfusion, neutrophils that are activated following ischemia-reperfusion, and peroxynitrite production from an interaction of superoxide with nitric oxide (the proximal tubular synthesis of which is induced by ischemic and toxic injury). ROS-mediated injury is also encountered in conditions associated with the availability of excessive free ferrous iron, such as hemoglobinuria, myoglobinuria, gentamicin, and cisplatin nephrotoxicity. Once generated, ROS can damage cells in many ways, including direct oxidation of membrane proteins, peroxidation of membrane lipids, and DNA damage. Yet, the role of ROS in ATN remains controversial. While several animal studies provided evidence of ROS generation during renal ischemia-reperfusion injury and a protective effect of exogenously administered antioxidants, other studies failed to reveal a protective effect of antioxidants. These contradictory results may be due to factors such as the duration of injury and timing of the intervention. Controlled trials using antioxidants in human ATN have not been done. Intracellular free calcium rises following ATP depletion due to impairment of pumps that normally extrude calcium from the cell or sequester calcium within the endoplasmic reticulum. This can result in mitochondrial damage, activation of proteases and phospholipases, generation of ROS, and cytoskeletal disruption. Calcium channel blockers (CCBs) have been shown to ameliorate ischemic renal injury in a variety of animal studies, although the mechanisms conferring the protection are unclear. They may include an improvement in renal hemodynamics, a membrane stabilizing effect on tubule epithelial cells, and a calmodulin antagonizing effect, in addition to the prevention of calcium overloading of cells. CCBs have also yielded encouraging results in human ATN. Administration of CCBs to both donors and recipients has been shown to reduce the prevalence of ARF following cadaveric kidney transplants; however, the beneficial effect of CCBs in this setting may be because of their ability to blunt the nephrotoxicity of the concomitantly administered cyclosporine. In addition, CCB administration prior to radiocontrast materials confers protection against nephrotoxicity. It appears, therefore, that the prophylactic use of CCBs prior to a potential renal insult, such as cold ischemia in cadaveric transplants or administration of contrast material, is beneficial but that CCBs are unlikely to be effective in established ATN. Activation of phospholipase has been demonstrated in hypoxia-induced injury to proximal tubules in animal models, presumably as a result of ATP depletion and increase in intracellular calcium. Phospholipase activation can result in breakdown of membrane phospholipids, disruption of cellular membranes, and subsequent cell death. Inhibitors of phospholipase A2 have been shown to confer protection against tubule cell injury in experimental ATP depletion. Activation of neutrophils recruited during reperfusion of ischemic kidneys has been implicated in subsequent renal cell injury. Activated neutrophils loosely adhere to the vascular endothelium via P-selectin-mediated interactions, become immobilized via interactions between the leukocyte adhesion molecule CD11/18 and the endothelial receptor intercellular adhesion molecule-1 (ICAM-1), and induce direct endothelial and tubule cell injury via release of reactive oxygen species. In experimental models, depletion of neutrophils or inhibition of neutrophil adhesion to endothelial cells (via administration of soluble P-selectin glycoprotein ligand or neutralizing antibodies to either ICAM-1 or CD11/18) significantly reduced the severity of ischemia-reperfusion injury. Alterations in tubule cell morphology ATN is characterized by heterogeneity in the morphologic response of various nephron segments. The cells lining the collecting duct tubules within the inner medulla and cortical ascending limbs are frequently not injured. Proximal tubule and mTAL cells display changes commensurate with the severity of the insult, with the majority of cells being injured sublethally and capable of complete recovery. More severely affected cells are lost by apoptosis, while the most severely injured cells undergo necrosis; however, even the sublethally injured cells undergo significant alterations in the actin-based cytoskeleton, which account for several of the functional consequences of ATN. The integrity of the actin-based cytoskeleton is crucial to several aspects of renal tubule epithelial cell biology, including the maintenance of asymmetric (polarized) distribution of integral membrane proteins, maintenance of the tight junctions, structure of microvilli, and cell-cell and cell-substratum interactions. Disruption of actin microfilaments following ischemic renal injury results in a series of cellular changes that have been demonstrated primarily in cultured cells and in animal models. First, loss of microvillus structure results in exfoliation of the brush border into the tubule lumen, which contributes to tubular obstruction. Second, loss of the barrier function of proximal tubule tight junctions contributes to the back-leak of glomerular filtrate. Third, loss of basolateral localization of the sodium, potassium–adenosine triphosphatase (Na, K-ATPase) and its redistribution to the apical membrane domain results in impaired transport of sodium, water, and other cotransported solutes. The apical mislocation of Na, K-ATPase has also been demonstrated in human ATN, and normalization of solute transport is dependent on reestablishment of the polarized phenotype. Fourth, loss of basal domain distribution of beta1-integrins and their redistribution to the apical domain results in loss of cell adherence to the substratum and the exfoliation of viable cells. This contributes not only to the cast formation and tubular obstruction but also to the back-leak via denuded areas of basement membrane. In addition, it may contribute to the abnormal adhesion between exfoliated cells, thereby promoting cast formation and obstruction. The explanation for the latter hypothesis lies in the finding that the detached viable cells contain receptor fragments of matrix proteins that bind avidly to the beta1-integrins expressed apically on neighboring exfoliated cells. This interaction requires the presence of the arginine-glycerol-asparaginase (Arg-Gly-Asp, or RGD) motif on the integrin receptors. In experimental ATN, infusion of short peptides containing the RGD motif significantly ameliorated cast formation and functional impairment, by preventing adhesion between exfoliated cells. Lethally injured tubule cells die via 2 distinct mechanisms. The most severely injured cells display a profound decrease in ATP levels and undergo necrosis. This is characterized by cell swelling, mitochondrial disruption, and loss of plasma membrane integrity, leading to the chaotic release of intracellular components into the extracellular space and activation of an inflammatory response. Less severely injured cells exhibit a partial ATP depletion, and activate apoptotic pathways. Apoptosis or programmed cell death is an energy-requiring process characterized by progressive cell shrinkage, nuclear condensation and fragmentation, plasma membrane blebbing, and disintegration of the cell into membrane-bound vesicles that are phagocytized rapidly without eliciting an inflammatory response. Apoptosis is best viewed as a packaging mechanism, whereby the cell essentially commits suicide and quietly exits the stage. Apoptotic cells can be detected in histologic sections only by specific techniques. A large body of evidence now exists attesting to the critical role of apoptosis, both in experimental ARF and in human ATN. Following brief periods of renal ischemia, apoptotic cells become evident within 24 hours of reflow. A second wave of apoptotic cells has been observed during the recovery phase of ARF, when it likely represents a mechanism for removal of unwanted or excessively proliferating cells, thereby facilitating the remodeling of injured tubules. The molecular mechanisms underlying the first wave of apoptosis are currently under intense investigation because selective inhibition of these pathways may constitute a powerful novel strategy for diminishing cell death in ATN. Factors influencing recovery In the absence of multiorgan failure, most patients with ATN regain most of the renal function. The recovery phase involves the restitution of cell polarity and tight junction integrity in sublethally injured cells, removal of dead cells by apoptosis, removal of intratubular casts by reestablishment of tubular fluid flow, and regeneration of lost renal epithelial cells. Following ischemia-reperfusion, there is a marked up-regulation of a number of genes that play important roles in renal tubule cell proliferation occurs, including epidermal growth factor (EGF), insulinlike growth factor-1 (IGF-1), fibroblast growth factor (FGF), and hepatocyte growth factor (HGF). In animals, exogenous administration of several of these growth factors has been shown to accelerate recovery from ischemic ARF; however, in a single human trial, IGF-1 did not prove to be beneficial when given to adults with ARF of various etiologies. Additional human studies with growth factors currently are under way. Heat shock proteins (HSP) are a group of highly conserved proteins that are expressed constitutively in normal cells and markedly induced in cells injured by heat, hypoxia, or toxins. They act as intracellular chaperones, allowing proper folding, targeting, and assembly of newly synthesized and denatured proteins. At least 2 families of HSPs, namely HSP-70 and HSP-25, have been shown to be overexpressed in renal tubule cells following ischemia-reperfusion injury in animals. HSP-70 may play a role in the restitution of cell polarity, and HSP-25 is an actin-capping protein that may assist in the repair of actin microfilaments in sublethally injured cells. The role for HSPs in human ATN remains to be elucidated. Frequency: In the US: Frequency varies greatly depending on the clinical context. ATN is the most frequent cause of hospital acquired ARF. In adults, prevalence of ATN is approximately 1% at admission, 2-5% during hospitalization, and 4-15% after cardio-pulmonary bypass. ATN occurs in approximately 5-10% of newborn ICU patients and 2-3% of pediatric ICU patients. Prevalence in children undergoing cardiac surgery is 5-8%. Mortality/Morbidity: Mortality rates vary widely according to the underlying cause and associated medical condition. For patients with community-acquired ATN without other serious comorbid conditions, the mortality rate is approximately 5%, and it has decreased over the past decades because of the availability of efficient renal replacement therapies. The mortality rate jumps to 80% among ICU patients with multiorgan failure, although death almost never is caused by renal failure. The most common causes of death are sepsis, cardiovascular and pulmonary dysfunction, and withdrawal of life support measures. Race: No significant racial predilection exists. Sex: Both sexes are affected equally. Age: ATN affects all age groups, although the causes differ from group to group. ATN is encountered more commonly in neonates and elderly persons because of the high frequency of comorbid conditions. CLINICAL Section 3 of 10 Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Bibliography History: Patients with hospital-acquired ATN frequently have no specific symptoms. The diagnosis is at times suspected when urine output diminishes and is usually made by the documentation of successive elevations in BUN and serum creatinine levels. Careful evaluation of the hospital course usually reveals the cause of ATN. In patients with community-acquired ATN, a thorough history and physical examination are invaluable in pinpointing the etiology. In children, the most common form is ischemic ATN caused by severe hypovolemia, shock, trauma, sepsis, burns, and major surgery. Also common is nephrotoxic ATN, caused by a variety of drugs. Their deleterious effect is markedly enhanced by hypovolemia, renal ischemia, or other renal insults. Fluid losses Severe vomiting and/or diarrhea are common causes of renal hypoperfusion in children. Significant fluid loss may also result from hemorrhage or burns. Loss of intravascular volume into the interstitial compartment accompanies major surgery, shock syndromes, and nephrotic syndrome. Children with fluid losses may complain of thirst, dizziness, palpitations, and fatigue. A history of acute weight loss and oliguria may be documented; however, ATN resulting from nephrotoxic drugs and from perinatal events are frequently of the nonoliguric type. Drugs In the presence of mild prerenal insufficiency, ingestion of seemingly innocuous medications that impair renal autoregulation can precipitate oliguric ATN; for example, NSAIDs inhibit the renal synthesis of vasodilator prostaglandins and can precipitate ATN when administered to febrile children with intercurrent dehydration. Cyclosporine, tacrolimus, and contrast agents are afferent arteriolar constrictors. Their nephrotoxicity is potentiated by preexisting hypovolemia because they inhibit the myogenic response of the afferent arteriole to renal hypoperfusion. Drugs that induce direct tubule cell damage include aminoglycosides; amphotericin B; cyclosporine; tacrolimus; antineoplastic agents, such as cisplatin and methotrexate; and contrast agents. Acyclovir and sulfonamides can precipitate and obstruct the tubular lumens, especially in children with diminished tubular fluid flow. Release of endogenous tubular toxins Myoglobinuric ATN may be encountered in a variety of clinical situations, including muscle trauma, prolonged seizures, malignant hyperthermia, snake and insect bites, myositis, severe hypokalemia and hypophosphatemia, and infections such as severe influenza. Hemoglobinuric ATN can accompany various states of hemolysis, including transfusion reactions, malaria, snake and insect bites, glucose 6-phosphate dehydrogenase deficiency, and mechanical causes such as extracorporeal circulation and cardiac valvular prostheses. Hyperuricosuric ATN is observed primarily during treatment of lymphoproliferative or myeloproliferative malignancies and presents as tumor lysis syndrome. Hypoxia In infants, ATN frequently complicates severe perinatal asphyxia, respiratory distress syndrome, hemorrhage, and cyanotic congenital heart disease. Older children with severe pulmonary or cardiac disease also are prone to ATN. Physical: Signs of ARF include hypertension; edema; anemia; and signs of congestive heart failure (CHF), such as hepatomegaly, gallop rhythm, and pulmonary edema. Signs of intravascular volume depletion include tachycardia, orthostatic hypotension, decreased skin turgor, dry mucous membranes, and changes in sensorium. Causes: Prevalent causes of ATN in neonates Ischemia - Perinatal asphyxia, respiratory distress syndrome, hemorrhage (eg, maternal, twin-twin transfusion, intraventricular), congenital cyanotic heart disease, shock/sepsis Exogenous toxins - Aminoglycosides, amphotericin B, maternal ingestion of ACE inhibitors or NSAIDs Endogenous toxins - Hemoglobin following hemolysis, myoglobin following seizures Kidney disease - Renal venous thrombosis, renal artery thrombosis; renal hypoplasia and dysplasia; autosomal recessive polycystic kidney disease; bladder outlet obstruction Prevalent causes of ATN in older children Ischemia - Severe dehydration; hemorrhage; shock/sepsis; burns; third space losses in major surgery, trauma, nephrotic syndrome; cold ischemia in cadaveric kidney transplant; near drowning; severe cardiac or pulmonary disease Exogenous toxins - Drugs that impair autoregulation (eg, cyclosporine, tacrolimus, ACE inhibitors, NSAIDs), direct nephrotoxins (eg, aminoglycosides, amphotericin B, cisplatin, contrast agents, cyclosporine, tacrolimus) Endogenous toxins - Hemoglobin release (eg, transfusion reactions, malaria, snake and insect bites, glucose 6-phosphate dehydrogenase deficiency, extracorporeal circulation, cardiac valvular prostheses), myoglobin release (crush injuries, prolonged seizures, malignant hyperthermia, snake and insect bites, myositis, hypokalemia, hypophosphatemia, influenza) DIFFERENTIALS Section 4 of 10 Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Bibliography Dehydration Oliguria Renal Cortical Necrosis Tumor Lysis Syndrome Renal Failure Resource Center Renal Failure Resource Center View all Renal Failure Articles Renal Failure CME Renal Failure Multimedia Library Quick Find Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Bibliography Click for related images. Related Articles Dehydration Oliguria Renal Cortical Necrosis Tumor Lysis Syndrome Continuing Education CME available for this topic. Click here to take this CME. Patient Education Diabetes Center Acute Kidney Failure Overview Acute Kidney Failure Causes Acute Kidney Failure Symptoms Acute Kidney Failure Treatment WORKUP Section 5 of 10 Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Bibliography Lab Studies: Urinalysis Careful examination of freshly voided urine is a rapid and inexpensive way of distinguishing prerenal failure from ATN. In prerenal failure, a few hyaline and fine granular casts may be observed with little protein, heme, or RBCs. Heme-positive urine in the absence of erythrocytes in the sediment suggests ATN from hemolysis or rhabdomyolysis. Broad, brown granular casts are typically found in ischemic or nephrotoxic ATN. Urinary indexes Simultaneous measurement of urinary and serum sodium, creatinine, and osmolality can help differentiate between prerenal azotemia (in which the reabsorptive capacity and concentrating ability of the kidney are preserved or enhanced) and ATN (in which these functions are impaired). In prerenal failure, urine specific gravity and the ratio of urine to plasma creatinine levels are high, and the urinary sodium concentration is low (Table 1). In contrast, the urine in ATN is isosthenuric with a low urine-to-plasma creatinine ratio and high urine sodium concentration. The fractional excretion of sodium (FeNa) is the percentage of filtered sodium that is excreted. It is calculated easily by the formula FeNa(%) = ([u/P]Na)/([u/P]Cr) x 100, where Na and Cr represent concentrations of sodium and creatinine in the urine (U) and plasma (P), respectively. The FeNa is typically more than 1% in ATN and less than 1% in prerenal azotemia. Be alert to the fact that FeNa may be low in intrinsic renal failure from glomerular diseases. Interpretation of urinary indexes requires caution. Collect blood and urine specimens before the administration of fluids, mannitol, or diuretics. Urine should be free of glucose, contrast material, or myoglobin. Urinary indexes suggestive of prerenal failure (FeNa <1) may be observed in the ATN of contrast nephropathy and rhabdomyolysis. Table 1. Urinary Indexes in ATN vs Prerenal Failure ATN Prerenal Urine specific gravity 1010 >1020 Urine sodium (mEq/L) >40 <10 Urine/plasma creatinine <20 >40 FeNa >2% <1% Blood urea nitrogen and serum creatinine The hallmark of established ARF is a daily increase in serum creatinine (by 0.5-1.5 mg/dL/d) and BUN (by 10-20 mg/dL/d) levels. In ATN, the BUN/creatinine ratio is usually around 10, as opposed to a ratio more than 20 commonly observed in prerenal failure (due to enhanced proximal tubular reabsorption of urea). However, the BUN/creatinine ratio may be misleading in patients whose conditions are wasting or in infants with physiologically low muscle mass. Elevations of BUN also can result from steroid therapy, parenteral nutrition, GI bleeding, and catabolic states. A spurious elevation in serum creatinine may be observed following the use of drugs that interfere with the tubular secretion of creatinine (cimetidine, trimethoprim) or drugs that provide chromogenic substrates (cephalosporins) that interfere with the Jaffe reaction for the determination of serum creatinine. Serum sodium: Hyponatremia is a common finding in ATN and is usually dilutional, secondary to fluid retention and administration of hypotonic fluids. Serum potassium Hyperkalemia is a common and often serious complication of ATN. Contributing factors include reduced GFR, reduced tubular secretion, metabolic acidosis (each 0.1 unit reduction in arterial pH raises serum potassium by 0.3-0.4 mEq/L), and associated catabolic state. Hyperkalemia is most pronounced in individuals with excessive endogenous potassium production, such as in rhabdomyolysis, hemolysis, and tumor lysis syndrome. Symptoms are nonspecific and may include malaise, nausea, and muscle weakness. Hyperkalemia represents a life-threatening emergency that must be treated promptly and aggressively, primarily because of its depolarizing effect on cardiac conduction pathways. Serum phosphate and calcium Hyperphosphatemia and hypocalcemia frequently complicate ATN. The phosphate excess is secondary to reduced renal excretion and can lead to hypocalcemia and calcium phosphate deposition in various tissues. Hypocalcemia results predominantly from hyperphosphatemia and impaired absorption of calcium from the GI tract because of inadequate 1,25-hydroxy vitamin D-3 production by the diseased kidneys. Determining ionized calcium concentration may be important because this unbound form of serum calcium determines physiologic activity. Acidosis increases the fraction of serum calcium that is in the ionized form, while correction of acidosis may decrease it; thus, overzealous bicarbonate therapy can acutely decrease ionized calcium. Severe hypocalcemia results in tetany, seizures, and cardiac arrhythmias. Acid-base balance The high anion gap metabolic acidosis of ATN is a consequence of impaired renal excretion of nonvolatile acids. Decreased tubular reabsorption of bicarbonate further contributes to the metabolic acidosis. Severe acidosis can develop in children who are hypercatabolic (shock, sepsis) or who have inadequate respiratory compensation. Complete blood count A mild-to-moderate anemia is commonly observed as a result of dilution and decreased erythropoiesis. Severe anemia should prompt a search for hemolysis from a variety of causes; it can result in hemoglobinuric ATN. These patients usually display elevated serum lactate dehydrogenase levels. Microangiopathic hemolytic anemia with schistocytes and thrombocytopenia are indicative of possible HUS, which is an important cause of intrinsic ARF in children. Prolonged ATN also can result in bleeding due to dysfunctional platelets. Other tests A suspicion of rhabdomyolysis may be confirmed by direct determination of urinary myoglobin and elevation of serum creatine kinase (specifically the CK3 isoenzyme). Children with rhabdomyolysis usually also display marked increases in serum potassium and phosphate. In the tumor lysis syndrome following cancer chemotherapy, a marked elevation in serum uric acid occurs along with hyperkalemia and hyperphosphatemia. Hypomagnesemia is a prominent finding in nephrotoxic ATN, particularly associated with gentamicin, amphotericin B, cisplatinum or pentamidine administration. Serum levels of nephrotoxins should be determined and serially followed, particularly when using gentamicin, vancomycin, cyclosporine, or tacrolimus. Although ARF is usually secondary to ischemic or nephrotoxic injury, other causes of intrinsic ARF should be kept in mind and excluded by history, physical examination, and laboratory evaluation. Laboratory evaluation should include urine cultures and serologic tests (including C3 and C4 in all patients) and lupus serologies and hepatitis profiles when appropriate. Imaging Studies: Renal ultrasound An ultrasound examination of the kidneys and bladder with Doppler flow is essential in the workup of ARF. Exceptions to this rule may include children with unmistakable prerenal failure from well-documented dehydration who respond promptly to fluid therapy or children with renal insufficiency secondary to obvious glomerular disease, hypoxia-ischemia, or exposure to nephrotoxins. Ultrasound provides important information regarding kidney size, contour, echogenicity, corticomedullary differentiation, and blood flow. In ischemic or nephrotoxic ATN, the kidneys are of normal size or slightly enlarged, with increased echogenicity. With prolonged ATN, renal cortical necrosis may result in decreased kidney size. Bilateral small scarred kidneys are indicative of chronic renal disease. Congenital disorders, such as polycystic kidney disease and multicystic dysplasia, are easily detected. Calculi and tumors are also evident. Hydronephrosis is suggestive of urinary tract obstruction, and accompanying hydroureter and thickened bladder wall are consistent with bladder outlet obstruction. A Doppler study is important in the evaluation of vascular obstruction. Radionuclide scans Radionuclide scans (functional scans with mercaptotriglycylglycine [MAG-3] or diethylenetriamine penta-acetic acid [DTPA]) are useful in the assessment of obstruction and may provide additional information regarding GFR, renal blood flow, and tubule function. Their major clinical use in children with ATN is in the immediate posttransplant period, when scans can help differentiate between ATN and transplant rejection. Other Tests: Perform an ECG if hyperkalemia is suspected or detected by laboratory tests. The following are sequential ECG changes in hyperkalemia: Tall peaked T waves Prolongation of PR interval Widening of QRS complex ST segment changes Ventricular tachycardia Terminal ventricular fibrillation Procedures: Renal biopsy In general, a kidney biopsy is not necessary in the initial evaluation; however, if prerenal and postrenal causes of ARF have been ruled out and an intrinsic renal disease other than ischemic ATN, nephrotoxic ATN, HUS, or postinfectious glomerulonephritis is a possibility, a renal biopsy may be valuable in establishing the diagnosis, guiding therapy, and assessing prognosis. Renal biopsy may be also useful in the immediate posttransplant period for the differentiation between ATN and acute rejection. Histologic Findings: See Pathophysiology. TREATMENT Section 6 of 10 Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Bibliography Medical Care: In this section, strategies for preventing ATN and managing fluid and electrolyte disturbances are briefly described. Short accounts of dialytic modalities and newer experimental therapeutic approaches are also included. Treatment of hypertension in ATN is considered in a separate article (see Hypertension). Prevention of ATN In clinical situations in which renal hypoperfusion or toxic injury is anticipated, administration of fluids, diuretics, mannitol, and low-dose dopamine have been used to prevent or reverse renal injury. Vigorous prophylactic fluid administration has been used successfully to prevent ATN following cardiac surgery, cadaveric kidney transplantation, major trauma, burns, hemoglobinuria, myoglobinuria, tumor lysis syndrome, radiocontrast administration, amphotericin B therapy, and cisplatin infusion. Ensuring adequate hydration prior to any of the above procedures is now an established standard of care. However, the role of diuretics, mannitol, and low-dose dopamine is more controversial. In one recent well-designed study using either low-dose dopamine or furosemide prior to cardiac surgery in adults, no renoprotective effect could be documented. The prophylactic use of diuretics or dopamine prior to the above procedures is not recommended at this time. Several studies, albeit uncontrolled, suggest that diuretics may be beneficial when administered during the early phase of ATN. Although they do not appear to alter the course of the ARF, they may convert an oliguric to a nonoliguric ARF, which is more easily managed because it obviates the need for fluid restriction and allows for maximal nutritional support. The current recommendation is that a trial of intravenous furosemide should be attempted in children with oliguria of less than 48 hours duration who have not responded to adequate hydration. The dose of furosemide should be in the high range (2-5 mg/kg). Some evidence suggests that in the prevention of crush syndrome, early administration of mannitol, before muscle toxins and breakdown products are released into the circulation, may protect from the development of ATN. Fluid management The major goal of fluid management is to restore and maintain intravascular volume. ATN may manifest with hypovolemia, euvolemia, or volume overload, and an estimation of fluid status is a prerequisite for initial and ongoing therapy. This is accomplished by measuring input and output, serial body weights, vital signs, skin turgor, capillary refill, serum sodium, and FeNa. Children with intravascular volume depletion require prompt and vigorous fluid resuscitation. Initial therapy includes normal saline or lactated Ringer solution at 20 mL/kg over 30 minutes. It can be repeated twice if necessary, after careful monitoring to avoid possible fluid overload. Potassium administration is contraindicated until urine output is established. If anuria persists after 3 fluid boluses (confirmed by bladder catheterization), central venous monitoring may be required to guide further management. Oliguria in the presence of volume overload requires fluid restriction and possibly intravenous administration of furosemide. Children with established ATN may not respond to furosemide; in which case, consider fluid removal by dialysis or hemofiltration, especially if signs of pulmonary edema are evident. Input and output records, daily weights, physical examination, and serum sodium concentration guide ongoing therapy. A bedside indicator of appropriate fluid therapy is a body weight decrease of approximately 0.5% per day as a result of caloric deprivation; serum sodium concentration should remain stable. A more rapid weight loss and increasing serum sodium indicate inadequate fluid replacement. An absence of weight loss with decreasing serum sodium suggests excess free water replacement. During the recovery phase, children develop significant polyuria and natriuresis and may become dehydrated if appropriate adjustments in fluid requirements are not made. Electrolytes and acid-base balance If serum potassium levels exceed 5.5-6.5 mEq/L, eliminate all sources of potassium from the diet or intravenous fluids and administer a cation exchange resin such as sodium polystyrene sulfonate (Kayexalate). Kayexalate requires several hours of contact with the colonic mucosa to be effective; the rectal route of administration is preferred. Complications of this therapy include hypernatremia and constipation. An attempt can be made to lower serum potassium concentration by increasing the dose of diuretics in those patients responding to them. Emergency treatment of hyperkalemia is indicated when serum potassium exceeds 6.5 mEq/L or tall peaked T waves are evident on the ECG. In addition to Kayexalate, administer intravenous sodium bicarbonate, which causes a rapid shift of potassium into cells. The magnitude of the potassium intracellular shift is variable, and thus bicarbonate is not reliable in lowering the K level. Such therapy should be used with caution because it can precipitate hypocalcemia and sodium overload. Sodium bicarbonate uptake of potassium by cells can also be stimulated by infusion of glucose and insulin or by beta-agonists (albuterol by nebulizer). The efficacy and convenience of nebulized albuterol has been well described in chronic hemodialysis patients with hyperkalemia; however, it can cause tachycardia, and the overall pediatric experience is limited. The presence of ECG changes requires the immediate administration of calcium gluconate (with continuous ECG monitoring) to counteract the effects of hyperkalemia on the myocardium. This therapy may precipitate bradycardia and other cardiac arrhythmias. The definitive therapy for significant hyperkalemia in oliguric ATN frequently includes dialysis. The forms of therapy outlined above serve to tide over the crisis while arrangements are being made for dialysis. The primary treatment of hyponatremia is free water restriction. Serum sodium of less than 120 mEq/L may require hypertonic (3%) sodium chloride infusion, especially if CNS dysfunction is present. Administration of hypertonic sodium chloride could precipitate CNS dysfunction and may be used only with extreme caution in critical care settings. Management of hyperphosphatemia includes dietary restriction and oral phosphate binders (calcium carbonate or calcium acetate). Hypocalcemia usually responds to oral calcium salts used for control of hyperphosphatemia but may require 10% calcium gluconate infusion or intravenous Calcitrol if severe. Metabolic acidosis of ATN is usually mild and does not require treatment. Moderate acidosis (pH <7.3) should be treated with oral sodium bicarbonate or sodium citrate. Severe acidosis (pH <7.2), especially in the presence of hyperkalemia, requires intravenous bicarbonate therapy. Adequate ventilation is necessary in order to exhale the carbon dioxide produced. Bicarbonate administration may precipitate hypernatremia or hypocalcemia. Children who cannot tolerate a large sodium load (ie, those with CHF) may be treated in an intensive care unit (ICU) setting with intravenous tromethamine (THAM), pending institution of dialysis. Medications Avoid nephrotoxic agents, as they may worsen the renal injury and delay recovery of function. Such agents include contrast media, aminoglycosides, and NSAIDs. Prescribing medication in ATN requires knowledge of the route of elimination, and modifications in dose or frequency should be made based on residual renal function. When making these adjustments, patients in the early phase of ATN with a rising serum creatinine level should be assumed to have a GFR of less than 10 mL/min, irrespective of the serum creatinine value. Dialysis The goal of dialysis is to remove endogenous and exogenous toxins and to maintain fluid, electrolyte, and acid-base balance until renal function returns. Indications for acute dialysis are not absolute, and the decision to use this therapy depends on the rapidity of onset, duration, and severity of the abnormality to be corrected. See Common indications for dialysis in ATN. The choice between hemodialysis and peritoneal dialysis depends on the overall clinical condition, availability of technique, etiology of the ATN, institutional preferences, and specific indications or contraindications. In general, peritoneal dialysis is a gentler and preferred method in infants and younger children. Specific contraindications include abdominal wall defects, bowel distention, perforation or adhesions, and communications between the abdominal and chest cavities. Hemodialysis has the distinct advantage of rapid correction of fluid, electrolyte, and acid-base imbalances, and may be the treatment of choice in hemodynamically stable patients, especially older children. Disadvantages include the requirement for vascular access, large extracorporeal blood volume, heparinization, and skilled personnel. An important advance has been the use of biocompatible synthetic dialysis membranes, such as polysulfone. These membranes should minimize complement activation and neutrophil infiltration into the kidney. Their use generally is recommended in children with ARF, although not all studies have documented beneficial effects. Over the past decade, continuous venovenous hemofiltration (CVVH) has emerged as an alternative therapy primarily for children with ATN who require fluid removal who are unstable or critically ill. The major advantage of this technique lies in the ability to remove fluid in a hypotensive child in whom hemodialysis may be relatively contraindicated and peritoneal dialysis inefficient. The patient requires the continuous presence of trained personnel and specialized equipment that are currently available only at select tertiary care centers. CVVH also can be modified easily to allow for significant solute removal, and as experience accumulates, this continuous but gentle modality may emerge as the dialytic therapy of choice for patients with ATN in the ICU. Some concern remains that dialysis actually may be detrimental to recovery of renal function in ATN. Institution of dialysis may decrease any residual urine output (which exacerbates intratubular obstruction), may induce episodes of hypotension (which further compromises renal perfusion), and may activate complement (which increases neutrophil infiltration into the kidney). Complement activation may be minimized by the use of biocompatible membranes, and CVVH may allow for dialysis with better hemodynamic control. Common indications for dialysis in ATN Fluid overload that is unresponsive to diuretics Fluid overload that hinders adequate nutritional support Hyperkalemia with oliguria Symptomatic acid-base imbalances Refractory hypertension Symptomatic uremia (pleuritis, pericarditis, CNS symptoms) Surgical Care: Patients with ATN secondary to obstruction frequently require urologic care. The site of obstruction determines the therapy. In neonates, obstruction of the bladder neck caused by posterior urethral valves must be immediately relieved by gentle insertion of a fine urethral catheter. The subsequent management of choice is endoscopic ablation of the valves. A temporary cutaneous vesicostomy may be required in a small infant. Consultations: Management of ATN requires specialized care by a pediatric nephrologist. Diet: Children with ATN are frequently in a highly catabolic state. Aggressive nutritional support is important. Adequate calories to account for maintenance requirements and supplements to combat excessive catabolism must be provided. Oral feeding is the preferred route of administration. Infants should receive a low-phosphorus diet (Similac PM 60/40), and older children should be placed on a low-potassium, low-phosphorus diet. Additional calories may be supplied by fortifying foods with Polycose and medium-chain triglyceride (MCT) oils. Children who are nauseous or anorexic may benefit from parenteral feedings or intravenous hyperalimentation. If adequate nutrition cannot be achieved because of fluid restriction, consider early institution of ultrafiltration or dialysis. Activity: Children with ATN are usually hospitalized, and activity is restricted; however, strict bed rest does not accelerate recovery. MEDICATION Section 7 of 10 Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Bibliography In this section, the use of medications for prevention of ARF and treatment of hyperkalemia, hyperphosphatemia, and metabolic acidosis are described. For the treatment of hypertension, see Hypertension. Hyperkalemia in oliguric ATN is a medical emergency that may be managed by shifting potassium into cells with sodium bicarbonate, glucose/insulin infusion, or beta-agonists; by increasing potassium excretion with exchange resins (sodium polystyrene) or loop diuretics (furosemide); or by dialysis. Protecting the myocardium from hyperkalemia is managed with IV calcium. Hyperphosphatemia may be initially managed with oral calcium to bind dietary phosphate. Oral citrate salts may be used to manage mild metabolic acidosis, whereas IV sodium bicarbonate is needed for severe metabolic acidosis. Drug Category: Loop diuretics -- In children with recent-onset oliguria from prerenal or toxic injury who are unresponsive to hydration, a trial of furosemide may convert the oliguric ATN to a nonoliguric type, which is managed more easily. These agents have a direct vasodilatory action and additionally may prevent tubular obstruction by increasing intratubular fluid flow.Drug Name Furosemide (Lasix) -- Increases excretion of water by interfering with the chloride-binding cotransport system, which, in turn, inhibits sodium and chloride reabsorption in ascending loop of Henle and distal renal tubule. Used for ATN prevention in children with oliguria duration <48 h who have not responded to adequate hydration. May also be considered for oliguria in the presence of volume overload. Also used for hyperkalemia to increase potassium excretion in the urine. Adult Dose 200-400 mg IV; may be repeated in 60 min if no diuretic response Pediatric Dose 2-5 mg/kg/dose IV; may be repeated in 60 min if no diuretic response Contraindications Documented hypersensitivity; oliguric ATN for >48 h or anuria >6-12 h Interactions Metformin decreases concentrations; interferes with hypoglycemic effect of antidiabetic agents and antagonizes muscle relaxing effect of tubocurarine; auditory toxicity appears to be increased with coadministration of aminoglycosides and furosemide; hearing loss of varying degrees may occur; anticoagulant activity of warfarin may be enhanced when taken concurrently with this medication; increased plasma lithium levels and toxicity are possible when taken concurrently with this medication Pregnancy C - Safety for use during pregnancy has not been established. Precautions Excessive diuresis may result in dehydration and worsening of ARF; can cause reversible or irreversible hearing loss, especially in the presence of severe renal impairment or concomitant aminoglycoside administration Drug Category: Alkalizing agents -- Sodium bicarbonate IV and oral sodium citrate are used as buffers that break down to water and carbon dioxide after picking up free hydrogen ions, thus counteracting acidosis by raising blood pH. IV sodium bicarbonate is also used to manage hyperkalemia.Drug Name Sodium bicarbonate -- Used to treat hyperkalemia. Causes a rapid shift of potassium into cells. The magnitude of the potassium intracellular shift is variable; thus bicarbonate is not reliable in lowering the K level by itself. Also used emergently to manage severe metabolic acidosis. Adult Dose 50-100 mEq IV over 10 min Pediatric Dose 1 mEq/kg IV over 10 min; may be repeated in 15 min if ECG changes persist Contraindications Patients diagnosed with alkalosis, hypernatremia, hypocalcemia, severe pulmonary edema, and unknown abdominal pain Interactions Incompatible with calcium salts, catecholamines, and atropine Urinary alkalinization, induced by increased sodium bicarbonate concentrations, may cause decreased levels of lithium, tetracyclines, chlorpropamide, methotrexate, and salicylates; Increases levels of amphetamines pseudoephedrine, flecainide, anorexiants, mecamylamine, ephedrine, quinidine, and quinine Pregnancy C - Safety for use during pregnancy has not been established. Precautions May precipitate hypernatremia, circulatory overload, hypocalcemia, metabolic alkalosis; avoid extravasation Drug Name Sodium citrate (Bicitra, Oracit) -- Manages mild metabolic acidosis and used as an alkalinizing agent when long-term maintenance of an alkaline urine is desirable. Adult Dose 1-2 mEq/kg/d PO divided bid Pediatric Dose Administer as in adults Contraindications Renal insufficiency and patients in sodium restricted diet Interactions Decreases therapeutic levels of lithium, chlorpropamide, methotrexate, tetracyclines and salicylates due to urinary alkalinization; increases toxicity of amphetamines, ephedrine, quinine and quinidine due to urinary alkalinization Pregnancy C - Safety for use during pregnancy has not been established. Precautions Dilute with water or juice and administer after meals; may cause diarrhea. Drug Category: Myocardium stabilizers -- The use of IV calcium does not lower serum potassium levels. It is used primarily to protect the myocardium from the deleterious effects of hyperkalemia (ie, arrhythmias) by antagonizing the potassium actions on the myocardial cell membrane.Drug Name Calcium gluconate (Kalcinate) -- Provides myocardial protection from hyperkalemia. Indicated if hyperkalemia is accompanied by ominous ECG changes beyond peaked T waves or if ECG changes persist after bicarbonate therapy. Adult Dose 10-30 mL of 10% solution IV over 5 min Pediatric Dose 1 mL/kg IV over 5 min with constant cardiorespiratory monitoring in an ICU; may be repeated in 15 min if ECG changes persist Contraindications Renal calculi, hypercalcemia, hypophosphatemia, renal or cardiac disease, digitalis toxicity Interactions Incompatible with sodium bicarbonate, phosphates, and sulfates May decrease effects of tetracyclines, atenolol, salicylates, iron salts, and fluoroquinolones; antagonizes effects of verapamil; large intakes of dietary fiber may decrease calcium absorption and levels Pregnancy B - Usually safe but benefits must outweigh the risks. Precautions May precipitate bradycardia and other cardiac arrhythmias; avoid extravasation Drug Category: Intracellular transporters -- Insulin and glucose (dextrose) cause a transcellular shift of potassium into muscle cells, thereby lowering (temporarily) potassium serum levels.Drug Name Dextrose and insulin infusion -- Used as an adjunctive to bicarbonate therapy to promote intracellular shift of potassium. Adult Dose Dextrose 50 g with regular insulin 5 U IV over 30 min Pediatric Dose Dextrose 0.5 g/kg with regular insulin 0.1 U/kg IV over 30 min Contraindications Diabetic coma if blood sugar levels are extremely high; severe dehydration Interactions Caution when administering parenteral fluids to patients receiving corticosteroids or corticotropin, especially if the solution contains sodium ions Pregnancy C - Safety for use during pregnancy has not been established. Precautions Insulin may precipitate hypoglycemia; dextrose may cause nausea, which may also occur with hypoglycemia; IV dextrose solutions may result in dilution of serum electrolyte concentrations or overhydration when there is fluid overload; caution in patients suffering from congested states or pulmonary edema; hypertonic dextrose given peripherally may cause thrombosis (administer instead through central venous catheter); caution in subclinical diabetes mellitus or carbohydrate intolerance; increased risk of inducing significant hyperglycemia or hyperosmolar syndrome if solution is administered rapidly, especially in patients with chronic uremia or carbohydrate intolerance Concentrated solutions should not be administered SC or IM; rates of dextrose infusion higher than 0.5 g/kg/h may produce glycosuria; at infusion rates of 0.8 g/kg/h the incidence of glycosuria is 5%; monitor fluid balance, electrolyte concentrations and acid-base balance closely; dextrose administration may produce vitamin B-complex deficiency Drug Category: Exchange resins -- Sodium polystyrene sulfonate is an exchange resin that can be used to treat mild-to-moderate hyperkalemia. Each mEq of potassium is exchanged for 1 mEq of sodium.Drug Name Sodium polystyrene sulfonate (Kayexalate) -- Indicated in all cases of hyperkalemia because it is the only modality (other than diuretics and dialysis) that actually removes excessive potassium from the body. Exchanges sodium for potassium and binds it in the gut, primarily in the large intestine, and decreases total body potassium. Onset of action after oral administration ranges from 2-12 hours and is longer when administered rectally. Adult Dose 50-100 g PO/PR in sorbitol Pediatric Dose 1 g/kg PO/PR in sorbitol; may repeat q4h Contraindications Documented hypersensitivity, hypernatremia Interactions Systemic alkalosis may occur if administered concurrently with magnesium hydroxide, aluminum carbonate or similar antacids, and laxatives Pregnancy C - Safety for use during pregnancy has not been established. Precautions Caution when administering to patients who can be adversely affected by a small increase in sodium loads such as those with severe hypertension, severe congestive heart failure, and marked edema; constipation, with the possibility of fecal impaction, may occur Drug Category: Phosphate binders -- ATN is frequently complicated by hyperphosphatemia and hypocalcemia, which respond to calcium-containing oral phosphate binders.Drug Name Calcium carbonate (Oystercal, Caltrate) -- Combines with dietary phosphate to form insoluble calcium phosphate, which is excreted in feces. Adult Dose 1-3 g PO tid with meals Pediatric Dose 0.5-3 g PO tid with meals Contraindications Renal calculi, hypercalcemia, hypophosphatemia, renal or cardiac disease, patients with digitalis toxicity Interactions Decreases ability of Kayexalate to bind potassium; may potentiate digoxin toxicity; may decrease effects of tetracyclines, atenolol, salicylates, iron salts, and fluoroquinolones; large intakes of dietary fiber may decrease calcium absorption and levels Pregnancy C - Safety for use during pregnancy has not been established. Precautions May precipitate hypercalcemia; adverse effects include dry mouth, nausea, vomiting, and constipation FOLLOW-UP Section 8 of 10 Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Bibliography Transfer: Children with ATN are best treated in a tertiary care institution with pediatric nephrology consultants. Transfer children with ATN who are hemody Link to comment Share on other sites More sharing options...
FL_Medic Posted July 31, 2006 Share Posted July 31, 2006 some of that was cut off, I said I thought ATN was angiotenson but couldn't find that. So I posted that answer. Name the flower that contains atropine and causes an anticholenergic reaction if ingested. Link to comment Share on other sites More sharing options...
Ace844 Posted July 31, 2006 Share Posted July 31, 2006 some of that was cut off, I said I thought ATN was angiotenson but couldn't find that. So I posted that answer. Name the flower that contains atropine and causes an anticholenergic reaction if ingested. I was going for the adult version that usually occurs after a 'shock' state.. But you answered correctly, nicely done.. The answer to your question is either Nightshade The Belladonna has dull green leaves and bell-shaped flowers that are an unremarkable shade of purple, which yield black, shiny berries measuring approximately 1 cm in diameter. It is an herbaceous shrub, and can grow to be approximately one metre tall. The leaves have an oily, "poison ivy"-like feel and can cause vesicular pustular eruptions if handled carelessly. Many animals, such as rabbits, birds and deer, seem to eat the plant without suffering harmful effects, though dogs and cats are affected. Many reports suggest that people have been poisoned by eating animals which have previously eaten Belladonna, though this has not been verified. Germination is often difficult due to the presence of germination inhibitors in the seeds. Belladonna is not common as a garden plant, and is considered a weed in some areas. It is not a very hardy perennial and is sensitive to being transplantated. Germination requires several weeks in warm, moist, absolutely sterile soil, usually far from normal garden conditions. or Datura inoxia (Devil's Weed) Datura strammonium (Jimson Weed or Thornapple) Datura brugmansia (Angel's Trumpet) is another well known plant which has recently been reclassified to the genus Brugmansia (Tree Datura). Other species may include: Datura arborea Datura aurea Datura candida Datura discolor Datura dolichocarpa Datura fatuosa Datura ferox Datura indica Datura metel Datura meteloides Datura sanguinea Datura suaveolens Datura tatula Datura vulcanicola Datura willemsi All of the species of Datura are leafy green plants with bright pink to white flowers. The flowers are all fragrant, with D. Inoxia having a very distinct aroma, very hard to mistake with any other plant. Datura grows all over the world, it would seem. The seeds are found in small fruit which are completely covered with short, sharp, spines (hence the name "Thornapple"). The stalks are bristly, and somewhat thin in comparison to the rest of the plant. The leaves are flat, mostly featureless, and can either be multi-edged (with between 4 and 15 points) or basically ovoid.. ACE Cor Pulmonale? Link to comment Share on other sites More sharing options...
FL_Medic Posted July 31, 2006 Share Posted July 31, 2006 Belladonna, correct!! Definition Cor pulmonale is an increase in bulk of the right ventricle of the heart, generally caused by chronic diseases or malfunction of the lungs. This condition can lead to heart failure. Description Cor pulmonale, or pulmonary heart disease, occurs in 25% of patients with chronic obstructive pulmonary disease (COPD). In fact, about 85% of patients diagnosed with cor pulmonale have COPD. Chronic bronchitis and emphysema are types of COPD. High blood pressure in the blood vessels of the lungs (pulmonary hypertension) causes the enlargement of the right ventricle. In addition to COPD, cor pulmonale may also be caused by lung diseases, such as cystic fibrosis, pulmonary embolism, and pneumoconiosis. Loss of lung tissue after lung surgery or certain chest-wall disturbances can produce cor pulmonale, as can neuromuscular diseases, such as muscular dystrophy. A large pulmonary thromboembolism (blood clot) may lead to acute cor pulmonale. Causes and symptoms Any respiratory disease or malfunction that affects the circulatory system of the lungs may lead to cor pulmonale. These circulatory changes cause the right ventricle to compensate for the extra work required to pump blood through the lungs. The right ventricle has thin walls and is crescent-shaped. The resulting pressure causes the right ventricle to dilate and bulge, eventually leading to its failure. Cor pulmonale should be expected in any patient with COPD and other respiratory or neuromuscular diseases. Initial symptoms of cor pulmonale may actually reflect those of the underlying disease. These may include chronic coughing, wheezing, weakness, fatigue, and shortness of breath. Edema (abnormal buildup of fluid), weakness, and discomfort in the upper chest may be evident in cor pulmonale. Diagnosis An electrocardiograph (EKG) will show signs such as frequent premature contractions in the atria or ventricles. Chest x rays may show enlargement of the right descending pulmonary artery. This sign, along with an enlarged main pulmonary artery, indicates pulmonary artery hypertension in patients with COPD. Magnetic resonance imaging (MRI) is often the preferred method of diagnosis for cor pulmonale because it can clearly show and measure volume of the pulmonary arteries. Other tests used to support a diagnosis of cor pulmonale may include arterial blood gas analysis, pulmonary function tests, and hematocrit. Treatment Treatment of cor pulmonale is aimed at increasing a patient's exercise tolerance and improving oxygen levels of the arterial blood. Treatment is also aimed at the underlying condition that is producing cor pulmonale. Common treatments include antibiotics for respiratory infection; anticoagulants to reduce the risk of thromboembolism; and digitalis, oxygen, and phlebotomy to reduce red blood cell count. A low-salt diet and restricted fluids are often prescribed. Alternative treatment Co-management of the patient with cor pulmonale should be coordinated between the medical doctor and the alternative practitioner. The first step in treatment is to determine the cause of the condition and to evaluate all organ systems of the body. Dietary considerations, for example, a low-salt diet and reduced fluid intake aimed at reducing the edema associated with cor pulmonale, can be supportive aspects of treatment. Prognosis The prognosis for cor pulmonale is poor, particularly because it occurs late in the process of serious disease. Prevention Cor pulmonale is best prevented by prevention of COPD and other irreversible diseases that lead to heart failure. Smoking cessation is critically important. Carefully following the recommended course of treatment for the underlying disease may help prevent cor pulmonale. ok, how do the coranary arteries recieve blood? Link to comment Share on other sites More sharing options...
AZCEP Posted August 2, 2006 Share Posted August 2, 2006 The coronary arteries are perfused by the backflow of blood against the Aortic valve. The RCA and LCA are located at the base of the aorta and are covered by the aortic valve during systole. Once the contraction of the left ventricle ends and the pressure gradient falls, the valve closes and the coronary arteries are perfused. http://medlib.med.utah.edu/WebPath/TUTORIA...RD/MYOCARD.html Coronary artery perfusion depends upon the pressure differential between the ostia (aortic diastolic pressure) and coronary sinus (right atrial pressure). Coronary blood flow is reduced during systole because of Venturi effects at the coronary orifices and compression of intramuscular arteries during ventricular contraction. Factors reducing coronary blood flow include: Decreased aortic diastolic pressure Increased intraventricular pressure and myocardial contraction Coronary artery stenosis, which can be further subdivided into the following etiologies: Fixed coronary stenosis Acute plaque change (rupture, hemorrhage) Coronary artery thrombosis Vasoconstriction Aortic valve stenosis and regurgitation Increased right atrial pressure 40 micron collateral vessels are present in all hearts with pressure gradients permitting flow, despite occlusion of major vessels. In general, the cross-sectional area of the coronary artery lumen must be reduced by more than 75% to significantly affect perfusion. Coronary atherosclerosis is diffuse (involving more than one major arterial branch) but is often segmental, and typically involves the proximal 2 cm of arteries (epicardial). What is a Mallory-Weiss tear? Link to comment Share on other sites More sharing options...
FL_Medic Posted August 2, 2006 Share Posted August 2, 2006 Definition A Mallory-Weiss tear occurs in the mucous membrane where the esophagus connects to the stomach, causing bleeding. Causes, incidence, and risk factors Mallory-Weiss tears are usually caused by forceful or prolonged vomiting or coughing. They may also be caused by epileptic convulsions. The tear may be followed by vomiting bright red blood or by passing blood in the stool. Any condition that leads to violent and lengthy bouts of coughing or vomiting can cause these tears. What is the bifurcation of the two main bronchi called? Link to comment Share on other sites More sharing options...
bassnmedic Posted August 2, 2006 Share Posted August 2, 2006 the carina What is your RX of choice in a Verapamil OD? And what is the coreect dosage? Link to comment Share on other sites More sharing options...
Ace844 Posted August 2, 2006 Share Posted August 2, 2006 the carina What is your RX of choice in a Verapamil OD? And what is the coreect dosage? 5-10 ml (0.5-1 Gm) of 10% calcium chloride. May repeat in 10 minutes. What is TETROLOGY OF FALLOT? Link to comment Share on other sites More sharing options...
FL_Medic Posted August 2, 2006 Share Posted August 2, 2006 5-10 ml (0.5-1 Gm) of 10% calcium chloride. May repeat in 10 minutes. What is TETROLOGY OF FALLOT? Tetralogy of Fallot What It Is Tetralogy of Fallot has four key features. A ventricular septal defect (a hole between the ventricles) and many levels of obstruction from the right ventricle to the lungs (pulmonary stenosis) are the most important. Also, the aorta (major artery from the heart to the body) lies directly over the ventricular septal defect, and the right ventricle develops thickened muscle. Because the aorta overrides the ventricular defect and there's pulmonary stenosis, blood from both ventricles (oxygen-rich and oxygen-poor) is pumped into the body. Sometimes the pulmonary valve is completely obstructed (pulmonary atresia). Infants and young children with unrepaired tetralogy of Fallot are often blue (cyanotic). The reason is that some oxygen-poor blood is pumped to the body. Surgical Treatment Tetralogy of Fallot is treated surgically. A temporary operation may be done at first if the baby is small. Complete repair comes later. Sometimes, the first operation is a complete intracardiac repair. How do you prepare a Tridil drip? And what would you use this on? Link to comment Share on other sites More sharing options...
FL_Medic Posted August 2, 2006 Share Posted August 2, 2006 By the way some history for you, Tetralogy of Fallot I believe lead to the first corrective heart surgery. This was done on infants at Johns Hopkins. They called them "blue babies". Link to comment Share on other sites More sharing options...
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