Therapeutic Hypothermia Improves Long-Term Survival and Blunts Inflammation in Rats During Resuscitation of Hemorrhagic Shock.

Abstract

We tested the hypothesis that therapeutic hypothermia (TH) improves survival and blunts inflammation in rats undergoing experimental hemorrhagic shock. Rats were randomized to TH (n = 16) or normothermia (n = 15). Hemorrhagic shock was induced by withdrawing blood to a fixed mean blood pressure (MBP) of 30 mmHg for 30 minutes followed by reinfusion of shed blood for the next 30 minutes. TH (target 32°C) was started at 5 minutes after MBP reached 30 mmHg and was maintained throughout blood volume resuscitation. In the normothermic control group, body temperature was maintained at 37°C during the procedure. Rats were allowed to recover for 6 weeks. TH significantly improved survival: 4 of 15 (26.7%) rats in the normothermic group and 11 of 16 (68.8%; p = 0.032) rats in the TH group survived 6 weeks. Recovery of MBP during the resuscitation phase was significantly improved and left ventricular fractional shortening was markedly increased in the TH group compared with the normothermic group. Brain infarction was observed in 3 of 4 surviving rats (75%) in normothermic group, and in only 1 of the 11 surviving rats (9%) in TH group. The neutrophil-to-lymphocyte ratio was lower in TH group (0.20 ± 0.02) compared with the normothermic group (0.32 ± 0.03; p = 0.003). TH influenced the levels of blood gases and blood counts, favoring hypothermia over control. TH significantly improved long-term survival and blunted the inflammatory response in experimental hemorrhagic shock.