Monitoring: Equipment and Computers
Background and Goal of Study: The kaolin-based activated clotting time assessed by the HEMOCHRON system (HkACT) is a clinical standard to monitor heparin therapy alone and combined with aprotinin during cardiopulmonary bypass (CPB). However, aprotinin is known to prolong not only celite-based ACT measurements but also kaolin-based ACT (1). Overestimation of ACT implies a potential hazardous risk of subtherapeutic heparin anticoagulation and must be avoided. Recently, a so-called aprotinin-insensitive ACT has been developed for the SONOCLOT Analyzer (SaiACT; Sienco Inc., Wheat Ridge, CO). The aim of our study was to evaluate and compare SaiACT with HkACT and anti-Xa activity in patients undergoing CPB.
Materials and Methods: 44 patients scheduled for elective cardiac surgery were studied. Heparin therapy was guided by HkACT. Blood samples were taken at baseline (T0), after heparin administration (200U/kg, 100U/kg; T1,2), on CPB, before (T3) and 15, 30, 60min after administration of aprotinin (2 Mio KIU; T4,5,6), and after protamine infusion (T7). HkACT, SaiACT and anti-Xa activity were measured at each time point, both ACT were measured in duplicate. Statistical analysis was done using Bland-Altman analysis, linear regression with Fisher's z-transformation and ANOVA with post-hoc Bonferroni-Dunn correction.
Results: A total of 352 blood samples were analyzed. Administration of heparin/protamine induced a significant increase/decrease of HkACT, SaiACT and anti-Xa. Compared to HkACT, SaiACT was significantly lower at T0-7: mean bias (SaiACT-HkACT) was −55 ± 113sec (−11 ± 17%; p < 0.01). Correlations of HkACT-anti-Xa (r2 = 0.41) and of SaiACT-anti-Xa (r2 = 0.48) were significantly different (p < 0.01). After administration of aprotinin (T4-6) 8% of SaiACT readings were <480sec, whereas all HkACT measurements were >480sec. Coefficient of variation was comparable for HkACT and SaiACT (HkACT = 7.9 ± 11.6%, SaiACT = 7.5 ± 7.9%).
Conclusion: These data indicate that SaiACT may be a valuable alternative to HkACT for guiding heparin therapy during CPB when aprotinin is used. The use of SaiACT may result in an increased administration of heparin.
1 J Extra Corpor Technol 2004; 36: 51-7.