Objectives: Excessive blood loss in a rat model of uncontrolled hemorrhage has been attributed to the vasodilatory effects of a droperidol-ketamine mixture used for anesthesia. The present study compared responses to droperidol-ketamine and pentobarbital with those responses of a control group without anesthesia during uncontrolled hemorrhage.
Design: Prospective, randomized, controlled trial.
Setting: University surgical research laboratory.
Subjects: Forty-five female Sprague-Dawley rats (210 to 275 g).
Interventions: Rats were randomly divided into three groups of 15 each according to the type of anesthesia: unanesthetized; pentobarbital; and droperidol-ketamine. A 75% tail resection was used to initiate hemorrhage. Mortality, survival time, and blood loss were monitored, and the differences between all three groups were tested using chi 2 test (mortality) and one-way analysis of variance (ANOVA) (survival and blood loss) for statistical significance.
Measurements and results: Mean blood loss amounts at 15 mins were 8.9, 13.6, and 22.4 mL/kg for the unanesthetized, pentobarbital, and droperidol-ketamine groups, respectively. Mortality rates for the three groups were 0%, 0%, and 53% at 30 mins and 60%, 33%, and 93% at 90 mins, respectively. Mean survival times for these groups were 94, 135, and 39 mins, respectively.
Conclusions: An excessive rate of blood loss due to the use of droperidol-ketamine anesthesia renders this model inappropriate for investigation of uncontrolled hemorrhage. The response of rats under pentobarbital anesthesia more closely approximates that of unanesthetized rats. However, the higher mortality rate despite the lesser hemorrhage observed in the latter group seems to indicate the existence of other factors (in addition to blood loss) that may contribute to the early death of these animals.