Coagulation Monitoring

Abstract

In Response: Casutt and Schüpfer1 commented on the concept of the platelet function (PF) measured by the Sonoclot Analyzer (Sonoclot Coagulation & Platelet Function Analyzer, Sienco, Arvada, CO). Figure 3B in our article2 presented an initial characterization of the Sonoclot Signature and attempted to illustrate that there is both a time component related to platelet activation as well as a clot retraction quality component. Although the graph only introduced the concept of PF, the text clearly states that PF as reported on the Sonoclot Analyzer is “derived from the timing and quality of the clot retraction.” The actual algorithm for the numerical PF result was beyond the scope of the article. It is a numerical integration of the Sonoclot Signature that sums both the speed of platelet activation and quality of clot retraction. A description of the algorithm is available by contacting the manufacturer, Sienco. Historically, many publications have used the earlier Time-to-Peak result as a useful PF indicator. As Dr. Casutt correctly points out, Time-to-Peak is limited as a PF indicator because it fails to include the quality of clot retraction in its result. Furthermore, regarding Dr. Casutt’s comment about the obvious influence of heparin, no PF interpretation should be attempted on samples anticoagulated with heparin that rely on thrombin formation to activate platelets. Activated tests that include heparinase to neutralize the effects of heparin are available for the Sonoclot Analyzer.3 Christoph K. Hofer, MD, DEAA Institute of Anesthesiology and Intensive Care Medicine Triemli City Hospital Zurich Zurich, Switzerland [email protected] Michael T. Ganter, MD, DEAA Institute of Anesthesiology University Hospital Zurich Zurich, Switzerland