Systemic reactions to tourniquet ischaemia.

In 15 patients, mean age 60 years, undergoing knee arthroplasty under lumbar epidural analgesia, changes in ECG, blood pressure, blood gases, serum potassium, acid-base status and serum creatine-phosphokinase were studied following release of a tourniquet applied for 70-135 min. During and after the ischaemia, the skin temperature of the leg operated on was monitored. Although dextran-70 was rapidly infused following tourniquet release, the blood pressure decreased significantly, due to a reduction in peripheral resistance. There were no signs of myocardial or pulmonary disturbances. Serum potassium in arterial blood increased significantly and reached a peak 3 min after tourniquet release. There was a tendency to metabolic acidosis, most pronounced after 3 min and caused by local lactate production. The skin temperature of the ischaemic leg fell progressively, which, combined with muscular relaxation, indicates a low metabolic rate. There was no evidence of local ischaemic muscular injury. It is concluded that the systemic changes after interruption of up to 2 h of tourniquet ischaemia are moderate and reversible, even in the elderly.