Activated coagulation time: one tube or two?

Abstract

OBJECTIVES: To compare activated coagulation time (ACT) management directed by a single ACT determination to that of the average of two simultaneously obtained ACT values. DESIGN: Prospective study. SETTING: Cardiac operating rooms of a university hospital. PARTICIPANTS: Patients undergoing surgery requiring cardiopulmonary bypass. INTERVENTIONS: All ACT determinations were performed in duplicate; patients were managed based on the average of the duplicate values, as is customary. Results of all tests were recorded on a spreadsheet, and the management dictated by a randomly chosen single result of each pair was compared with the management directed by the average value of each pair. Predetermined criteria were set for preference of one testing method over the other. Patients were grouped according to preoperative heparin exposure, and results of the two groups were compared. MEASUREMENTS AND MAIN RESULTS: One hundred patients underwent 683 paired celite ACT determinations. In 565/683 tests (83%), both methods called for identical heparin management responses. Management by the single-tube method would have resulted in supplemental heparin administration 34% more often than management by the average method. The single-tube method would have resulted in withholding supplemental heparin 13 times when the average method called for supplemental heparin administration, a 16% occurrence. The results of the patients with and without preoperative heparin exposure were not significantly different. CONCLUSIONS: The results of this study suggest the use of a two-tube average method to guide heparin administration for cardiopulmonary bypass. Preoperative heparin exposure did not influence this outcome.