Don't see a problem with giving the first NTG to a hypertensive or normotensive patient without a line. I can even see giving a second dose without a line if the pressure stays good and there is significant relief after the first dose. Usually if the patient has a decent BP I will get the ASA and NTG on board before I grab the IV and 12 lead anyway. If the pressure is low or looks lower than it should be, I might try to grab the 12 lead first to look for a RVI.
Even then, I don't think a RVI automatically precludes nitrate therapy, just warrants extreme caution, that caution including fluid therapy and thus an IV.
