Early isotonic saline resuscitation from uncontrolled hemorrhage in rats.

BACKGROUND: Attempts to modify traditional fluid resuscitation have been based on animal models that evaluate several variables including anesthesia. This study presents the effects of early saline resuscitation from severe uncontrolled hemorrhage unanesthetized rats. METHODS: Sixty-three female Sprague-Dawley rats were equally divided into three groups: group A, nonresuscitated; and groups B and C, resuscitated ;with isotonic saline (40 and 80 mL/kg, respectively). Hemodynamics, blood loss, survival time, and mortality were recorded for 360 minutes after the hemorrhage, which was initiated by 75% resection of the tail. RESULTS: In group C, 80 mL/kg of saline significantly lowered mortality (24% vs 76% and 71% for groups A and B, respectively) with concomitant increases in mean survival time (241 +/- 103 min vs 146 +/- 108 and 175 +/- 92 min for groups A and B, respectively). There were no statistically significant differences in blood loss, hematocrit, or hemodynamic parameters among the groups. CONCLUSIONS: Early and adequate isotonic saline resuscitation of unanesthetized rats improved outcome despite continuing hemorrhage. The significantly lower mortality rate and increased survival time were not a result of transiently improved arterial pressure and did not correlate with blood loss. No significant bleeding increases were noted in the resuscitated groups.

Effects of anesthesia on a model of uncontrolled hemorrhage in rats.

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.

The effects of isotonic saline volume resuscitation in uncontrolled hemorrhage.

In the present study, the effects of early isotonic fluid resuscitation on uncontrolled hemorrhage in rats under pentobarbital anesthesia were assessed. Forty-five female Sprague-Dawley rats, weighing between 230 and 295 grams, were anesthetized and cannulated. Uncontrolled hemorrhage was initiated by a 75 percent tail resection, and the rats were randomly divided into three groups: group 1, no resuscitation; groups 2 and 3, saline solution administration over a four minute interval (40 and 80 milliliters per kilogram, respectively), 15 minutes after the initial hemorrhage. Changes in blood pressure, blood loss and mortality rates were recorded and the rats were observed for up to 360 minutes. The mortality rates were 73, 40 and 53 percent for groups 1, 2 and 3, respectively. The corresponding average survival times for these groups were 135, 195 and 178 minutes. The difference between groups 1 and 2 were above the 95 percent confidence level using the chi-square test (mortality) and the Student's t test. The average total blood loss in groups 2 and 3 was 31.7 and 41.4 milliliters per kilogram of body weight; when compared with group 1 (24.6 milliliters per kilogram), the difference between the two latter groups (1 and 3) was statistically significant with a p < 0.001. These results suggest that early infusion of isotonic fluid improves survival time and reduces short term mortality in uncontrolled hemorrhage regardless of the associated increases in blood loss.

Isotonic saline resuscitation in uncontrolled hemorrhage under various anesthetic conditions.

OBJECTIVE: The authors evaluated the effect of early fluid resuscitation with isotonic saline (NaCl, 0.9%) on uncontrolled hemorrhage in rats under different anesthetic conditions. SUMMARY/BACKGROUND DATA: Recently, it has been suggested that administration of fluids to patients during uncontrolled hemorrhage may produce adverse effects, and a postponement of resuscitation until surgical control of bleeding was recommended. Past clinical trials were inconclusive, and the results of recent experimental studies were affected by use of vasoactive anesthetics. METHODS: One hundred thirty-five female Sprague-Dawley rats were randomly divided into three groups: group 1--unanesthetized; group 2--anesthetized with sodium pentobarbital; and group 3--anesthetized with a mixture of droperidol and ketamine. Uncontrolled hemorrhage was initiated with a 75% tail resection, and each group was further subdivided into three subgroups for the following treatment: (A) no resuscitation; (B) 40 mL/kg of isotonic saline; or (C) 80 mL/kg of isotonic saline, administered 15 minutes after the initiation of hemorrhage. Blood loss volume and survival time were recorded, and animals were observed up to 360 minutes. RESULTS: At 6 hours, nonresuscitated animals of all groups exhibited the highest mortality rates (93%, 73%, 100% in groups 1, 2, and 3, respectively). Resuscitation significantly improved the survival; lowest mortality rates were observed after resuscitation with 80 mL/kg in groups 1 and 3 (33%) and 40 mL/kg in group 2 (40%). Fluid infusion increased hemorrhage rates in all anesthetized rats. No such increases in bleeding were observed in group 1. CONCLUSIONS: Resuscitation with isotonic saline improved mortality in uncontrolled hemorrhage, even with concomitant increases in hemorrhage rates, under all three anesthetic conditions tested. Unanesthetized rats bled less than the animals under anesthesia and did not exhibit an increased blood loss in response to fluid infusion.