IS A STANDARD REGIME FOR ANTICOAGULATION WITH HEPARIN IN UNSTABLE ANGINA ADEQUATE

Aim: To establish the proportion of patients with unstable angina in w hom adequate anticoagulation is achieved using a standard regime of in travenous heparin. Method: A prospective series of 108 Emergency Depar tment attendees over a six-month period with a clinical diagnosis of u nstable angina for whom anticoagulation with heparin was prescribed we re included in the study. The standard regime was a 5000 unit bolus fo llowed by an intravenous infusion of 1000 units per hour (1200 units i f the patient's weight was greater than 80 kg), with subsequent adjust ments being made by reference to a nomogram. The activated partial thr omboplastin time (APTT) was measured at six and 12 hours after treatme nt began. Two commonly used criteria for adequate heparinisation were compared: 1. APTT greater than 1.5 times control and 2. APTT in the ra nge 60-85 seconds. Results: There were valid data for 90 patients at s ix hours and 79 at 12 hours. Compared to the criterion for adequate an ticoagulation of APTT greater than 1.5 times the control, 25% of patie nts were subtherapeutic at six hours and 12% at 12 hours. Compared to the criterion APTT greater than 60 seconds, 53% of patients were subth erapeutic at 6 hours and 47% at 12 hours. At 6 hours, 26% of patients were over-anticoagulated as defined as APTT greater than 85 seconds. T his had reduced to 13% by 12 hours. Conclusions: In the context of rec ent research suggesting that an APTT of greater than 1.5 times the con trol is sufficient to reduce complications in unstable angina, our res ults demonstrate that a standard regime of heparinisation will achieve this goal in the majority of patients within 6 hours of starting hepa rin therapy. However, if an APTT of 60-85 seconds is the goal, this st andard regime is inadequate.