Background: Activated clotting time (ACT) values during percutaneous transluminal coronary angioplasty (PTCA) after the initial 10,000 U heparin bolus are often below target values of 350 or 400 s (Hemochron) and have to be supplemented with additional heparin. This study evaluated the initial 10 min post-heparin bolus clotting time value using a body surface area (BSA)-adjusted heparin bolus versus the traditional 10,000 U heparin bolus.
Hypothesis: Body surface area adjustment of initial heparin dosing prior to PTCA will be more effective in reaching target ACT values compared with the 10,000 U heparin bolus method.
Methods: Twenty-seven patients receiving the BSA-adjusted heparin bolus were compared with 27 age- and gender-matched controls who had received the traditional heparin bolus. The adjusted heparin bolus formula used was [BSA(m2)/1.3m2] x 10,000 U of heparin.
Results: The success rate at reaching the target value of 400 s was 13 of 27 (48.1%) and 2 of 27 (7.4%) for the BSA-guided and 10,000 U heparin-guided groups, respectively (p < 0.01). The success rate at reaching the 350 s target value was 25 of 27 (92.6%) and 6 of 27 (22.2%) for the BSA-guided and 10,000 U heparin-guided groups, respectively (p < 0.01). The 95% confidence intervals for the difference in success between the BSA-guided and 10,000 U heparin-guided groups were 0.19-0.62 and 0.52-0.89 for the 400 s and 350 s ACT targets, respectively.
Conclusion: Body surface area adjustment of initial heparin dosing is a more effective method of reaching the initial ACT target values of 350 and 400 s compared with the traditional method prior to PTCA. This conclusion applies to the Hemochron ACT device and arterial samples, and adjustments may need to be made for other devices and/or venous samples.