Objestive To investigate the effects of nitroprusside induced hypotension on cognitive function after total hip replacement and the serum S-100 level in reflecting postoperative cognitive dysfunction (POCD). Methods Forty patients (age>65 yr) undergoing total hip replacement were assigned to two groups, randomly. In one group, the mean arterial pressure was decreased about 30% by sodium nitroprusside. In another group, the MAP was set constant as control. Serum values of S-100 were determined preoperatively and 0 2 h and 24 h postoperatively. Neuropsychological tests (Mini-Mental State Examination MMSE) for detecting POCD were performed preoperatively and the 4th day after the operation. A decline of more than 2 scores in MMSE results was regarded as POCD. Results According to our definition, 7 patients had POCD. There were no significant differences in MMSE test in two groups (P>0.05). Those patients had POCD showed higher serum concentrations of S-100 than those without POCD, especially at 0, 2 h postoperatively (P<0.05). Conclusion Nitroprusside induced hypotension would not impair cognitive function in old patients after total hip arthroplasty. S-100 appears to be suitable in the assessment or incidence of cognitive dysfunctions postoperatively.
