Effects of hypertonic/hyperoncotic treatment and surgical evacuation after acute subdural hematoma in rats.

OBJECTIVE The treatment of acute subdural hematoma (ASDH) consists mainly of surgical evacuation of the hematoma. It is conceivable that early preoperative neuroprotection with hypertonic/hyperoncotic treatment (HHT) can improve survival rates. The present study investigated the benefit of treatment with hypertonic/hyperoncotic solution on functional and histologic outcome as supportive therapy accompanying surgical intervention. DESIGN Laboratory experiment. SETTING University laboratory. SUBJECTS Male Sprague-Dawley rats weighing 296-350 g (n = 56). INTERVENTIONS ASDH was induced through subdural infusion of 400 microL of autologous venous blood. Thirty minutes after subdural blood infusion, the rats received either HyperHAES (7.2% saline/6% hydroxyethyl starch) or vehicle (NaCl 0.9%) intravenously, followed by surgical evacuation of the hematoma 1 hr after ASDH induction in those rats scheduled for surgical treatment. The experiment was divided into two parts: an acute study, which explored acute effects of HHT on blood variables, ASDH-induced changes of intracranial pressure (ICP), and cerebral perfusion pressure (CPP), and a chronic study, which investigated the chronic effects of HHT, surgical blood clot evacuation, and the combination of both on the functional and histologic outcome following ASDH (12 days). MEASUREMENTS AND MAIN RESULTS In the acute study, HHT expectedly raised the serum sodium concentration and lowered hematocrit. ASDH increased ICP and decreased CPP in all groups. HHT improved CPP by reducing ICP. In the chronic study, all treated groups showed a better recovery with respect to neurologic function and neuronal cell death compared with the vehicle-treated ASDH group. HHT with surgical evacuation or HHT alone improved functional and histologic outcome slightly more than surgical evacuation alone. CONCLUSIONS In this rat model, HHT led to a decrease of ICP after ASDH. This significantly improved functional and histologic outcome, which was comparable to the effects after blood evacuation alone. The combination of evacuation of subdural blood and early HHT improved histologic outcome further but not significantly, which was due to the strong effects of single treatments and a ceiling effect of the combined treatment in this model.