Neurobiochemical markers of brain ischemia in patients subjected to endoscopic skull base surgery under controlled hypotension.

BACKGROUND: Previous studies showed that moderate hypotension used to control bleeding during extensive endoscopic skull base procedures may cause a decrease in blood flow velocity (BFV) in the middle cerebral artery (MCA). We assessed possible metabolic consequences of reduction of arterial pressure applied in endoscopic skull base operations. METHODS: The serum concentrations of neuron specific enolase (NSE) and S-100 protein were measured in 15 patients operated on with reduced hemodynamic parameters (hypotensive group) and in 10 individuals operated on under normotensive conditions (normotensive group). Concentrations of NSE and S-100 were assessed preoperatively, as well as 24 h and 48 h postsurgery. Blood flow velocity in the MCA was evaluated with transcranial color Doppler sonography. RESULTS: An increase in NSE concentration was demonstrated in 5 out of 6 patients from the hypotensive group in whom BFV in the MCA dropped below normal reference range during surgery. An association between both phenomena was confirmed on statistical analysis. Neither the rise of S-100 concentration nor postoperative neurological deficits were detected in any of the studied individuals. CONCLUSIONS: Controlled hypotension during skull base procedures can result in postoperative increase in NSE serum concentration, a phenomenon suggestive for a degree of brain ischemia. Noticeably, the rise of NSE level occurs in subjects in whom BFV in the MCA decreased below normal reference limit during the surgery. Although neither S-100 protein level increase nor neurological deficits were detected postoperatively, further studies of the safety of hypotension applied during endoscopic skull base operations are warranted.