Mild hypothermia improves survival during hemorrhagic shock without affecting bacterial translocation

Accidental hypothermia in patients with hemorrhagic shock (HS) is associated with increased mortality. However, experimental mild and moderate hypothermia has beneficial effects. The mechanisms for beneficial effects of hypothermia have not been completely understood. Therefore, the aim of this study was to investigate the effect of hypothermia on survival, bacterial translocation (BT), and remote pulmonary injury in a controlled HS model in rats.

HS was achieved by blood withdrawal through femoral vein. Rats in the normothermia group (group I) were maintained at 37 degrees C. Mild hypothermia group (group II) was observed at 32 degrees C that was spontaneously induced by exposure to ambient temperature. Moderate hypothermia of 28 degrees C was actively induced by external cooling in group III for 90 min. Survival and neurological deficit scores (NDS) were recorded at 24th hr. Mesenteric lymph nodes, liver and spleen samples were collected. Myeloperoxidase (MPO) and malondialdehyde (MDA) levels were measured in lung tissue.

Blood pressure significantly increased in hypothermia groups. Mild hypothermia significantly increased survival. No difference was found in BT rates in groups. Hypothermia was found to significantly decrease the NDS points in group III, compared to group I. There was no difference in lung tissue MPO levels among groups. Lung tissue MDA levels increased significantly in groups II and III.

Mild hypothermia improved blood pressure, survival, and neurological outcome with a possible detrimental effect on pulmonary ROS production during HS in rats. These effects of hypothermia are not associated with BT.