• Rita Paniccia, Sandra Fedi, Fiorella Carbonetto, Daniela Noferi, Paolo Conti, Brunella Bandinelli, Betti Giusti, Lucia Evangelisti, Paola Pretelli, Mara F G Palmarini, Rosanna Abbate, and Domenico Prisco.
• Dipartimento di Area Critica Medico-Chirurgica, Sezione di Clinica Medica Generale e Cliniche Specialistiche, Centro di Riferimento Regionale per la Trombosi, Florence, Italy. r.paniccia@dac.unifi.it
• Anesthesiology. 2003 Jul 1;99(1):54-9.

BackgroundActivated clotting time (ACT) is used to monitor heparin therapy during cardiopulmonary bypass, interventional cardiology, and hemodialysis. Traditionally, ACT is performed by use of the Hemochron system. Recently, a new device, the i-STAT system, has been introduced to measure ACT. The aim of this study was to correlate the performances of these two systems and to compare ACT values with heparin levels.MethodsOne hundred sixty-five samples from 29 patients undergoing cardiopulmonary bypass or hemodialysis were assayed in duplicate with two Hemochron and two i-STAT devices. Heparin levels were determined by anti-factor Xa assay.ResultsThe Hemochron ACT ranged from 88 to 1,028 s, and the i-STAT ACT ranged from 80 to 786 s. Heparin plasma levels ranged from 0.01 to 10.8 U/mL. Bland-Altman analysis showed a mean difference between the two methods of 24 +/- 101 s. Strong relationships between anti-factor Xa activity and Hemochron ACTs (r2 = 0.69, P < 0.001) and i-STAT ACTs (r2 = 0.79, P < 0.001) were observed. During cardiac surgery, significant correlations were found: Hemochron, r2 = 0.61, P < 0.001 and i-STAT, r2 = 0.74, P < 0.001. During hemodialysis, relationships between anti-factor Xa activity and ACTs were found: Hemochron, r2 = 0.62, P < 0.001 and i-STAT, r2 = 0.55, P < 0.001.ConclusionsDuring cardiopulmonary bypass procedure and hemodialysis, i-STAT provides measurements of clotting time quite similar to Hemochron ACT, which were significantly correlated with heparin levels.

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