Activated clotting time (ACT) monitoring of intraoperative heparinization in peripheral vascular surgery.

We conclude that (1) the activated clotting time (ACT) is an accurate method of monitoring anti-coagulation during peripheral vascular surgery and can easily be performed by a technician in the operating room or at the bedside; (2) an initial heparinizing dose of 120 to 130 units/kg is adequate in 95 per cent of the patients; (3) the ACT should be maintained at greater than twice the control values (180 to 200 seconds), which required supplementation within 2 hours in 21 per cent; (4) the response to heparin is twofold: an initial sensitivity or resistance followed by an independent and variable rate of consumption; (5) the patient's heparin dose-response curve should be used to calculate the amount of supplemental heparin needed to maintain the ACT at a safe level; (6) protamine should be given if the ACT at the conclusion of the operation is greater than 150 seconds (50 per cent of our patients); and (7) a final ACT 15 to 30 minutes postoperatively should be obtained to ensure adequate reversal or to detect heparin rebound or depletion of clotting factors.