Achieving target antifactor Xa activity with a heparin protocol based on sex, age, height, and weight

Study Objectives. To develop and validate an improved unfractionated heparin (UFH) dosage protocol, using antifactor Xa levels as the outcome variable. Design. Prospective case series. Setting. A 625-bed, adults-only, private, tertiary care teaching hospital. Patients. Three hundred seventy-two patients receiving UFH for eight different indications were in the protocol derivation group. One hundred ninety-seven patients were in the final validation group. Intervention. Variables that predicted successful UFH treatment were determined by analysis of variance and regression. Measurements and Main Results. Sex, age, height, weight, UFH dosage, and antifactor Xa levels were variables. A regression model using sex, age, height, and weight was superior to a weight-only model in predicting UFH dosage. Target-range antifactor Xa levels were achieved with the new protocol in 122 (87%) of 140 patients within 24 hours of start of therapy. Conclusion. A UFH dosage protocol based on patient sex, age, height, and weight produced improved initial target antifactor Xa levels compared with a weight-based protocol. The protocol is computerized and easy to apply.