[The effect of controlled hypotension during spinal surgery on kidney function]

The effect of controlled hypotension on renal function in patients operated on for idiopathic scoliosis of the spine was examined (n = 20). The deformity was corrected under general anesthesia by posterior fusion using Harrington's instrumentation during controlled hypotension induced by sodium nitroprusside. The control group included 20 patients suffering the same deformity and operated on in the same way but without hypotension. Renal function tests were performed before and during the operation and continuously for 102 h after surgery. In the group with controlled hypotension (medium arterial pressure 8.0 kPa) there was a significant decrease in creatinine clearance during the operation (0.70 ml/s) compared with that in the control group (1.30 ml/s) and with the value before surgery (1.70 ml/s). At the end of hypotension, the average clearance value of creatinine increased up to 2.0-2.2 ml/s within 42 h. In the group of control patients (medium arterial pressure 11.5 kPa) the creatinine clearance persisted at a mildly decreased level (1.3 ml/s) during surgery and for a further 30 h after. The sodium retention characteristic of hyperaldosteronism was less marked in the patients with controlled hypotension. We did not observe any biochemical findings indicating retention of nitro substances. Controlled hypotension induced by sodium nitroprusside at surgical treatment of the vertebral column does not cause any impairment of the renal function either during surgery or as a late sequela.