Hemodynamic changes associated with tourniquet use under epidural anesthesia for total knee arthroplasty

Epidural anesthesia is administered commonly for total knee arthroplasty, a procedure using a thigh tourniquet. Tourniquet use has been associated with intraoperative hypertension and with occasional circulatory collapse after deflation. The purpose of this study was to define the hemodynamic changes in this setting.

We prospectively studied 373 consecutive patients having a total knee arthroplasty performed under epidural anesthesia, with continuous electrocardiogram and radial artery pressure monitoring. Results were analyzed using Student's t-test, correlation coefficients, analysis of variance, or chi-square analysis. Alpha was set at 0.01.

There was a 4 +/- 11 mmHg rise in mean arterial pressure throughout the period of tourniquet application (p less than 0.001); no clinically significant hypertension occurred. After tourniquet deflation, there was a 19.2 +/- 12% reduction in mean arterial pressure, occurring within one minute. The magnitude of mean arterial pressure reduction failed to correlate with any clinical parameter other than vasopressor use. There was a small subset of patients who had a fall in heart rate and a more profound degree of hypotension after tourniquet deflation, but these patients could not be identified before tourniquet release.

In this setting, tourniquet-induced hypertension is rare. However, hypotension after deflation is common, occurs rapidly, and correlates poorly with clinical parameters.