Controlled hypotension in hip joint surgery. An assessment of surgical haemorrhage during sodium nitroprusside infusion.

Controlled hypotension, combined with light balanced anaesthesia, was employed during total hip replacement operations on 25 patients. Sodium nitroprusside (Nipride, Roche), in the form of a 0.01 per cent (100 micrograms/ml) infusion, was used as a hypotensive agent. The mean arterial blood pressure (MABP) was lowered from 108 to 64 mmHg (range 60--70) (P less than 0.001). The average blood loss during the operations was 212 ml and none of the patients required homologous blood transfusion. In comparison with 25 normotensive patients undergoing similar surgery, the difference in the mean volume of haemorrhage between the two groups was 826 ml (P less than 0.001). The difference in the total haemorrhage, however, between the same two groups was 518 ml (mean) (P less than 0.01). The results were compared with those of another investigation in which epidural anaesthesia was used to diminish bleeding during surgery on the hip.