Hyperventillation facilitates retun of pupil symmetry?

[rocket]

Hi all, long time no post.

I've been reading the PEPP (Pediatric Education for Prehospital Professionals) course book lately. Something in the Trauma section caught my attention and I wonder if y'all could lend me your collective experience with it.

One of the recommendations in the text for dealing with head trauma patients who present with pupil asymmetry is to mildly hyperventilate (the book isn't right here in front of me so I'm paraphrasing here) "..until the pupil asymmetry returns". Again without the text in front of me I cannot verify the edition or publication date so I cannot say for certain if I'm reading the most recent edition of the PEPP text.

I am aware of the controversy surrounding the use of hyperventilation in traumatic brain injury. The NYS advisory (I am a NYS EMT) covers it quite well and the recommendations are clear (and I will follow them, giving specific attention to evidence of transtentorial herniation which might include pupil asymmetry).

http://www.health.state.ny.us/nysdoh/ems/policy/s97-03.htm

So here is my question. I suppose it's more of a curiosity thing than anything else...

Has anyone here actually observed a reversal of pupil asymmetry while a patient has been hyperventilated? I understand that hyperventilation can reduce intracranial pressure (at the potential expense of cerebral blood flow) but can it do so to such an extent that you can get a pupil "back to normal" right away ?

Thanks!

-Trevor

[Medic2588]

I've never seen the pupil return to normal size, but that's not to say it definitely won't. Hyperventilating the patient (about 24 breathes per minute) helps to reduce the pressure of herniation syndrome, but I'm not sure if it reverses it.

Devin

[Ridryder 911]

I am a PEPP & PALS instructor, & I was informed that new standards was to be out this spring. Studies have shown not to hyperventiallte head injuries patients.. due to it does cause constriction of cerebral ateries. Yes it does reduce ICP by reducing bleeding but, also prevents cereberal tissue from recieving adequate perfusion.

Here is a link with the pathophysiology and treatment of why pupillary response is asociated with oxygenation.

http://www.aic.cuhk.edu.hk/web8/severe_blunt_head_injury.htm

Be safe,

R/R 911

[Guest DELETED]

DELETED

[dgmedic]

Yup, it fixes it...by blowing the other pupil!!

-dg

[actualparamedic]

I have never seen the reversal of pupil asymmetry, nor even heard that it was possible without gross reversal of ICP

I've never seen the pupil return to normal size, but that's not to say it definitely won't. Hyperventilating the patient (about 24 breathes per minute) helps to reduce the pressure of herniation syndrome, but I'm not sure if it reverses it.

Medibrat and Devin are correct. There's no direct correlation between abnormal pupillary reaction secondary to brain swelling and hyperventilation.

Reversal of abnormal pupils (if it occurs) parallels with the resolution of brain swelling/brainstem compression. This has everything to do with pharmaceutical or neurosurgical intervention, when indicated.

Some traumatic, metabolic, CVA-related or anoxic insults to the brain will progress to brain death no matter what type of field or hospital treatment is undertaken.

[Dustdevil]

I've seen reversal at least once that I specifically recall. But I certainly wouldn't speculate that it was due to hyperventilation. Guy had a major stroke while plowing his field out in the middle of nowhere. I worked on him for an hour or so, lowering his pressure and ICP with everything in the box. Hyperstat, mannitol, Solu Medrol, Valium. Filled up the foley bag. The emesis basin too. By the time we made it to the hospital, his pupils had indeed equaled out. It caught me by surprise and I remember wondering to myself if I hadn't been mistaken in noting them as unequal in my initial assessment.

By the way, I would like to say how happy I am to see a basic taking such serious interest in mundane pathophysiology. =D>

[pmedic623]

Studies have shown not to hyperventiallte head injuries patients.. due to it does cause constriction of cerebral ateries. Yes it does reduce ICP by reducing bleeding but, also prevents cereberal tissue from recieving adequate perfusion.

Be safe,

R/R 911

Took a medic refresher last year and the RN teaching this day brought this same point out about hyperventilation and over oxygenation of the head injury pt causing constriction........

[Ace844]

Hello Everyone,

Here's some recent data which puts an interesting perspective on this topic...

Hope this Helps,

ACE844

("Emergency Medicine Journal 2006;23:440-441; doi:10.1136/emj.2005.030247;© 2006 by BMJ Publishing Group Ltd @ and British Association for Accident and Emergency Medicine; ORIGINAL ARTICLE;Variability in pupil size estimation;

A Clark1, T N S Clarke2, B Gregson3, P N A Hooker2 and I R Chambers1; 1 Regional Medical Physics Department, Newcastle upon Tyne General Hospital, Newcastle upon Tyne, UK; 2 Anaesthesia Department, Newcastle upon Tyne General Hospital, Newcastle upon Tyne, UK;3 Neurosciences Department, Newcastle upon Tyne General Hospital, Newcastle upon Tyne, UK

Correspondence to MrAndrew Clark; Regional Medical Physics Department, Newcastle General Hospital, Newcastle upon Tyne, NE4 6BE, UK; andy.clark@nuth.northy.nhs.uk”)

Background: The clinical estimation of pupil size and reactivity is central to the neurological assessment of patients, particularly those with or at risk of neurological damage. Health care professionals who examine pupils have differing levels of skill and training, yet their recordings are passed along the patient care pathway and can influence care decisions. The aim of this study was to determine if any statistical differences existed in the estimation of pupil size by different groups of health care professionals.

Methods: A total of 102 health care professionals working in the critical care environment were asked to estimate and record the pupil size of a series of 12 artificial eyes with varying pupil diameter and iris colour. All estimations were performed indoors under ambient lighting conditions.

Results: Our results established a statistically significant difference between staff groups in the estimation of pupil size.

Conclusion: The demonstrated variability in pupil size estimation may not be clinically significant. However, it remains desirable to have consistency of measurement throughout the patient care pathway.

[AZCEP]

The recommendation is as follows:

--If a patient presents with bilateral dilated pupils, ventilate at 5/min greater than normal for the age. (child-20+5=25, infant-30+5=35) Continue this until the pupils constrict, then ventilate at normal ranges for the age.

--If a patient presents with asymmetrical pupillary size, ventilate as above until symmetry returns, then return to normal rates.

Seems that we are telling people it is okay to hyperventilate as long as you pay close attention to the pupils. :roll: This may work in an operating theater where there are enough people to dedicate someone to this function. Everywhere else will end up with hyperventilated, hypocapneic, brain herniations.