Anaphylaxis

ÎEpinephrine may be administered every 5 to 10 minutes as necessary. If the clinician deems it appropriate, the 5 minute interval between injections can be liberalized to promote more frequent administration. ÎEpinephrine should be administered as soon as the diagnosis of anaphylaxis is suspected. ÎAlthough the diagnosis of anaphylaxis usually depends on involvement of two organ systems (eg, skin plus respiratory, skin plus cardiovascular), anaphylaxis may present as an acute cardiac or respiratory event or with hypotension as the only manifestation of anaphylaxis. ÎFor suspected anaphylaxis, even if it involves only one system such as the skin, epinephrine administration may be indicated. ÎIntravenous administration may be considered in patients poorly responsive to intramuscular or subcutaneous epinephrine, where there is inadequate time for emergency transport, or prolonged transport is required. Comment: No established dosage or regimen for intravenous epinephrine in anaphylaxis is recognized. However, a prospective study demonstrated the efficacy of a 1:100,000 solution of epinephrine (1.0 mg [1 mL of 1:1000] in 100 mL saline) intravenously by infusion pump at an initial rate of 30-100 mL/hr (5-15 mg/ min), titrated up or down depending on clinical response or epinephrine side effects (toxicity). Inferences regarding intravenous dosing may also be drawn from the emergency cardiac care consensus guidelines for intravenous epinephrine for adults and children. An epinephrine infusion may be prepared by adding 1 mg (1 mL) of 1:1000 dilution of epinephrine to 250 mL of D5W to yield a concentration of 4.0 mg/ mL. This 1:250,000 solution is infused at a rate of 1 mg/min (15 drops/minute using a micro-drop apparatus [60 drops/minute = 1 mL = 60 mL/hr]), titrated to desired hemodynamic response, increasing to a maximum of 10.0 mg/min for adults and adolescents. A dosage of 0.01 mg/kg (0.1 mL/kg of a 1:10,000 solution up to 10 mg/ min; maximum dose – 0.3 mg) is recommended for children. Alternative pediatric dosage by the ''Rule of 6'' is as follows: 0.6 x body weight (in kg) = # of mg diluted to total 100 mL saline; then 1 mL/hr delivers 0.1 mg/kg/min. (See full text article for infusion guidelines in children.) An alternative epinephrine infusion protocol has been suggested for adults with anaphylaxis. ÎBecause of the risk of potentially lethal arrhythmias, epinephrine should be administered intravenously only in profoundly hypotensive patients or patients in cardio/respiratory arrest who have failed to respond to intravenous volume replacement and several injected doses of epinephrine. Comment: In situations where hemodynamic monitoring is available (eg, emergency department, intensive care facility), continuous hemodynamic monitoring is recommended if epinephrine is given intravenously. However, use of intravenous epinephrine should not be precluded in a scenario where such monitoring is not available if the clinician deems its administration is essential after several intramuscular/subcutaneous epinephrine injections. If intravenous epinephrine is considered under these special circumstances, monitoring by available means (eg, every-minute blood pressure and pulse measurements and electrocardiogram monitoring, if available) should be considered. 11

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