Comparison of fluid therapy for resuscitation of hemorrhagic shock in intact rat and hypothermic kidney denervated rats

Recent studies have demonstrated that hypothermia after hemorrhagic shock (HS) can decrease need of fluid therapy and increase arterial pressure that results in increase the survival rate. But it has not been determined how hypothermia causes these beneficial effects. This study reviews hypothermia effects in this area. This is an experiential study in which 24 rats were divided into four groups. Rats were anesthetized by pentobarbital. In groups 1and3, bilateral renal sympathectomy was done and in the groups 2 and 4 renal nerves remained intact and only lateral incisions were done to preserve similar conditions. Then rats underwent HS phase (phase I) for 90 minutes, by withdrawing 4-6 ml of blood during 10 mines. After shock induction, only in groups 1 and 2, body temperature was lowered to 32oC. At the end of phase I, rats underwent resuscitation phase (phase II) by reinfusion of blood & additional Ringer Lactate to retain normal arterial pressure. Stage II lasted 60 minutes. In hypothermic groups (1 and 2) in comparison to normothermic groups (3 and 4) there was less blood or fluids needed for resuscitation (p<0.05). Arterial pressure before shock was the same in all groups but at the end of phaseII was higher in hypothermic ones (p<0.05). It seems that mild hypothermia has beneficial effects on survival of animals with HS. Although it is obvious that intact kidneys have vital role in maintaining body fluid balance during HS, but it seems hypothermic rats requires lesser fluid therapy even without nerve of kidney. More studies could be probably required to confirm this.