SUPERIORITY OF BLOOD OVER SALINE RESUSCITATION FROM HEMORRHAGIC-SHOCK- A P-31 MAGNETIC-RESONANCE SPECTROSCOPY STUDY

Objective To study the relation between blood and saline administratio n, postresuscitation hematocrit (Hct) level, and metabolic recovery af ter hemorrhagic shock. Summary Background Data It is generally believe d that crystalloid can be substituted, in whole or in part, for blood during resuscitation of hemorrhagic shock. This is based on the belief that Hct can be safely reduced but should not fail below a critical l evel. Methods Male rats weighing 200 g were subjected to an isobaric h emorrhagic shack at a mean arterial pressure of 30 mmHg for 14 minutes , after which they were randomized to one of three resuscitation regim ens. Control group (n = 36) were resuscitated by return of all shed bl ood. Mid-Hct (n = 39) and low-Hct (n = 60) groups were depleted of one third and one half of their circulating blood volumes, respectively, and were resuscitated with three times that volume of normal saline. S keletal muscle intracellular energetics and pH were measured serially using P-31 magnetic resonance spectroscopy at baseline, during shock, and after resuscitation. Arterial blood was sampled at the same time p oints. The number of surviving animals in each group at 24 hours was r ecorded. Results After resuscitation, surviving rats in the low-Hct gr oup demonstrated a greater consumption of high-energy phosphocreatine stores than did the other groups (control = 0.479 +/- 0.003, mid-Hct = 0.465 +/- 0.004, low-Hct = 0.457 +/- 0.007, mean +/- standard error o f the mean; p < 0.01 low-Hct vs. other groups by analysis of variance) . The rats that received saline resuscitation developed a relative int racellular acidosis (control = 7.29 +/- 0.02, mid-Hct = 7.25 +/- 0.02, low-Hct = 7.23 +/- 0.02; p < 0.05 controls vs. other groups by analys is of variance). At 24 hours, the death rates were significantly diffe rent among the groups: control = 1 of 36 rats (2.8%), mid-Hct = 6 of 3 9 (15.4%), and low-Hct = 14 of 60 (23.3%) (p < 0.05 by chi square anal ysis). Conclusion The oxygen-carrying capacity of resuscitation fluid has an important impact on intracellular metabolism and outcome.