Cerebral effects and blood sparing efficiency of sodium nitroprusside-induced hypotension alone and in combination with acute normovolaemic haemodilution

The combined reduction of oxygen-carrying capacity and perfusion pressure d uring the combination of acute normovolaemic haemodilution (ANH) and contro lled hypotension (CH) raises concerns of hypoperfusion and ischaemic injury to the brain. Forty-two patients undergoing radical prostatectomy were pro spectively allocated to receive CH induced by sodium nitroprusside (mean ar terial pressure (MAP) 50 mm Hg), a combination of CH+ANH (post-ANH haematoc rit 29%; intraoperative MAP 50 mm Hg), or standard anaesthesia (control). S erum levels of the brain-originated proteins neuron-specific enolase (NSE) and protein S-100, blood loss, transfusion requirements, adverse effects, a nd postoperative recovery profile were compared among the three groups. Int raoperative blood loss in the CH group (mean (SD)) (788 (193) ml) and CH+AN H group (861 (184) ml) was significantly less than in the control group (13 35 (460) ml). Significantly fewer total units of allogeneic packed red bloo d cells (PRBC) were transfused in the patients receiving hypotensive anaest hesia (CH, 3 units; CH+ANH, 2 units; control, 17 units). There was no diffe rence in immediate postoperative recovery profile among the three groups as determined by the emergence from anaesthesia and time to discharge from th e postanaesthesia care unit. Serum S-100 protein concentrations increased s ignificantly in all groups from baseline to peak concentrations 2 h postope ratively (CH 0.25 (0.11) mug litre(-1); CH+ANH 0.31 (0.12) mug litre(-1); c ontrol 0.31 (0.10) mug litre(-1)). A return to baseline values was seen wit hin 24 h postoperatively in all patients. No changes in NSE concentrations were seen. Our observations suggest that CH and CH+ANH were effective in re ducing blood loss and transfusion requirements in patients undergoing radic al prostatectomy. Increased serum S-100 protein concentrations imply a dist urbance in astroglial cell membrane integrity and an increased endothelial permeability of the blood-brain barrier. There were no associations between serum S-100 protein or NSE and adverse cognitive effects. Further work nee ds to be done to determine the prognostic importance of S-100 protein and N SE as surrogate variables of postoperative cerebral complications.