A comparison of epinephrine only, arginine vasopressin only, and epinephrine followed by arginine vasopressin on the survival rate in a rat model of anaphylactic shock

Background. Epinephrine and more recently arginine vasopressin (AVP) alone or in combination have been proposed in patients with anaphylactic shock, but few experimental data exist. The authors investigated the effects of epinephrine only, AVP only, or epinephrine followed by AVP in a model of anaphylactic shock. Methods: Ovalbumin-sensitized Brown Norway rats were anesthetized, intubated, and shock induced with ovalbumin. Rats (n = 6/group) were randomly allocated to receive 5 min after shock onset: (1) saline (no-treatment group); (2) two boluses of epinephrine followed by continuous infusion (epinephrine group); (3) AVP bolus followed by continuous infusion (AVP group); (4) epinephrine bolus followed by AVP continuous infusion (epinephrine + AVP group). Mean arterial pressure (MAP) and skeletal muscle oxygen pressure (Ptio(2)) were measured. Continuous infusion rates were titrated to reach MAP values of 60 mmHg. Survival was analyzed. Results: Without treatment, MAP and Ptio(2) decreased rapidly with 0% survival. In the epinephrine group, MAP and Ptio(2) recovered after an initial decrease, with 84% survival. In the AVP group, MAP was partially restored and subsequently decreased; Ptio(2) values decreased to values similar to those in the no-treatment group; survival was 0%. In the epinephrine + AVP group, MAP and Ptio(2) values increased more slowly as compared with the epinephrine group; survival was 100%. Conclusions: In this model of anaphylactic shock, early treatment with epinephrine followed by continuous epinephrine or vasopressin infusion resulted in an excellent survival rate, whereas vasopressin only resulted in a 100% death rate. These experimental results suggest that epinephrine must still be considered as the first-line drug to treat anaphylactic shock.