Thursday, April 30, 2015

The Use Of adrenaline in anaphylaxis

IM vs SC - which is preferred?
According to the AHA 2005 on CPR & ERC, it says:
"Absorption and subsequent achievement of maximum plasma concentration after subcutaneous administration is slower and may be significantly delayed with shock. Thus, intramuscular (IM) administration is favored."

Thus, although it does not mention that SC route cannot be used, this is not the preferred route.

IV route can and should be used if:
"...if anaphylaxis appears to be severe with immediate life-threatening manifestations."

The AHA guidelines says that IV is to be used if "it appears" to be severe. It doesn't say to wait until anaphylactic shock develops, then only gives IV route.

The dose & rate is almost the same for both IM and IV respectively: 0.5 mg in 20 min (IM) and in 25 min (IV).

In this blog post (first link), a nice little pearl is given: put in 1 ampoule of 1 mg of adrenaline in a bag of 1000 ml NS. In our case, since 1 L IV fluid is seldom used, put in 0.5 mg in 500 ml NS. Use an 18-gauge cannula and run it wide open. In this way, the patient would receive about 20-30 mL/min (or 20-30 mcg/min) of epinephrine, which is similar to the recommended push-dose epi (0.1 mg or 100 mcg over 5 minutes; or 0.5 mg over 25 min as recommended).

Finally, remember also that in patients where their beta receptors have been blocked, aka, on beta blocker, adrenaline may not work. In such cases, glucagon should be given. Glucagon has inotropic, chronotropic and vasoactive effects that are independent of ╬▓-receptors, and it also causes endogenous catecholamine release. See this article.

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