Effects of hetastarch on rewarming after prolonged deep hypothermia in rats

Other than reducing cardiac output and increasing vascular resistance, hypo thermia-induced hypovolemia has also bren recognized as a risk Factor for r ewarming shock. Previously, we demonstrated that hetastarch can minimize hy povolemia and prolong survival in hypothermia. Therefore, it is quite possi ble that a successful rewarming can also be achieved by hetastarch treatmen t. To test this, rats were rewarmed after maintaining the body temperature (Tb) at 19 degreesC for 24 hr and the effects of different regimens of heta starch treatment (single or double) on successful rewarming were evaluated. Treating the animal with a single dose of 6% hetastarch (5 ml) at either e arly or Inter stage of hypothermia (3 and 20 h after hypothermia, respectiv ely) did nor significantly alter the success of rewarming. In contrast, rat s receiving two doses of hetastarch, at h 3 and 20 after hypothermia, marke dly enhanced rewarming success. Rheologically, treating the animal with 2 d oses of hetastarch significantly delayed the characteristic rise of haemato crit and cell fragility during hypothermia. This treatment also maintained plasma volume at higher levels as compared to the saline controls. These re sults indicate that a successful rewarming after prolonged hypothermia can be achieved through rectification of rheological changes impeding tissue mi crocirculation.