Effect of induced-hypothermia on short-term survival after volume-controlled hemorrhage in pigs

To examine whether induced hypothermia could prolong short-term survival after volume-controlled hemorrhagic shock (HS).

Fifteen pigs with systemic heparin underwent blood withdrawal of 30 ml/kg over 15 min under spontaneous breathing with halothane anesthesia. The pigs were divided into three groups of five pigs each: Group 1, hemorrhage plus hypothermia with extracorporeal shunt circulation (ECSC); Group 2, hemorrhage plus normothermia with ECSC; and Group 3, hemorrhage alone. For Groups 1 and 2, arteriovenous ECSC was performed for 20 min during HS. The re-infused shunt blood was cooled down to approximately 15 degrees C in Group 1, whereas it was returned at 37.5 degrees C in Group 2. The pigs in Group 3 had no ECSC and were left at room temperature. All pigs were observed until their death or for a maximum of 240 min.

The mean pulmonary artery temperature (T(pa)) of Group 1 animals decreased to 34.5 degrees C at 15 min after the initiation of ECSC, and thereafter remained at 35.5 degrees C after undergoing ECSC. The T(pa) values for Groups 2 and 3 animals remained at 37.5 degrees C throughout the experiment. All five pigs in Group 1 survived until 240 min, whereas all pigs in Group 2 and 3 of five pigs in Group 3 died before 215 min after blood withdrawal. A life table analysis revealed significantly increased survival in Group 1 compared with Group 2 (P<0.01) and Group 3 (P<0.05).

In lightly anesthetized pigs during volume-controlled HS, induced hypothermia may prolong their short-term survival for reasons that remain to be clarified.