title: Monitoring activated clotting time for combined heparin and aprotinin application: in vivo evaluation of a new aprotinin-insensitive test using Sonoclot.
abstract: OBJECTIVE
  Kaolin-based activated clotting time assessed by HEMOCHRON (HkACT) is a clinical standard for heparin monitoring alone and combined with aprotinin during cardiopulmonary bypass (CPB). However, aprotinin is known to prolong not only celite-based but also kaolin-based activated clotting time. Overestimation of activated clotting times implies a potential hazardous risk of subtherapeutic heparin anticoagulation. Recently, a novel 'aprotinin-insensitive' activated clotting time test has been developed for the SONOCLOT analyzer (SaiACT). The aim of our study was to evaluate SaiACT in patients undergoing CPB in presence of heparin and aprotinin.
  
  
  METHODS
  Blood samples were taken from 44 elective cardiac surgery patients at the following measurement time points: baseline (T0); before CPB after heparinization (T1 and T2); on CPB, before administration of aprotinin (T3); 15, 30, and 60 min on CPB after administration of aprotinin (T4, T5, and T6); after protamine infusion (T7). On each measurement time point, activated clotting time was assessed with HkACT and SaiACT, both in duplicate. Furthermore, the rate of factor Xa inhibition and antithrombin concentration were measured. Statistical analysis was done using Bland and Altman analysis, Pearson's correlation, and ANOVA with post hoc Bonferroni-Dunn correction.
  
  
  RESULTS
  Monitoring anticoagulation with SaiACT showed reliable readings. Compared to the established HkACT, SaiACT values were lower at all measurement time points. On CPB but before administration of aprotinin (T3), SaiACT values (mean+/-SD) were 44+/-118 s lower compared to HkACT. However, the difference between the two measurement techniques increased significantly on CPB after aprotinin administration (T4-T6; 89+/-152 s, P=0.032). Correlation of ACT measurements with anti-Xa activity was unchanged for SaiACT before and after aprotinin administration (r2=0.473 and 0.487, respectively; P=0.794), but was lower for HkACT after aprotinin administration (r2=0.481 and 0.361, respectively; P=0.041). On CPB after administration of aprotinin, 96% of all ACT values were classified as therapeutic by HkACT, but only 86% of all values were classified therapeutic if ACT was determined by SaiACT. Test variability was comparable for SaiACT and HkACT.
  
  
  CONCLUSIONS
  The use of SaiACT may result in more consistent heparin management that is less affected by aprotinin and a corresponding increase in heparin administration for patients receiving aprotinin.
authors.affiliation: Institute of Anesthesiology and Intensive Care Medicine, Triemli City Hospital Zurich, Switzerland.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Ganter
authors.forename: Antoinette
authors.initials: A
authors.lastname: Monn
authors.forename: Reza
authors.initials: R
authors.lastname: Tavakoli
authors.forename: Michele
authors.initials: M
authors.lastname: Genoni
authors.forename: Richard
authors.initials: R
authors.lastname: Klaghofer
authors.forename: Lukas
authors.initials: L
authors.lastname: Furrer
authors.forename: Hanspeter
authors.initials: H
authors.lastname: Honegger
authors.forename: Christoph K
authors.initials: CK
authors.lastname: Hofer
mesh_terms: D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000627:therapeutic use*; D007611:Aprotinin / Q000627:therapeutic use*; D001780:Blood Coagulation Tests / Q000379:methods; D006348:Cardiac Surgical Procedures; D002315:Cardiopulmonary Bypass; D004347:Drug Interactions; D016903:Drug Monitoring / Q000379:methods*; D005260:Female; D006488:Hemostasis, Surgical; D006490:Hemostatics; D006493:Heparin / Q000627:therapeutic use*; D006801:Humans; D007430:Intraoperative Care / Q000379:methods; D008297:Male; D008875:Middle Aged; D019106:Postoperative Hemorrhage / Q000517:prevention & control; D014914:Whole Blood Coagulation Time
chemical_list: D000925:Anticoagulants; D006490:Hemostatics; D006493:Heparin; D007611:Aprotinin