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Hemochron® low range activated clotting time might be useful in post-cardiac surgical patients
- Sujesh Bansal, C. C. Harle, A. Knowles, and N. Gavin (27 November 2006)
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Sujesh Bansal Lancashire Cardiac Centre, Blackpool, UK, C. C. Harle, A. Knowles, and N. Gavin
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Hemochron® low range activated clotting time might be useful in post- cardiac surgical patients ___________________________________________________________ S. Bansal, C.C. Harle, A. Knowles, N. Gavin Correspondence to DrBansal@doctors.org.uk Editor, We read with interest the study by Tremey et al on the use of Hemochron® low range activated clotting time (ACT-LR) to monitor anticoagulation during vascular surgery.1 We feel ACT-LR, which seems accurate for monitoring heparin anticoagulation at anti-Xa activity below 0.8 u ml-1 could be an important monitoring tool which can replace traditional activated clotting time (ACT). ACT is misused in many clinical situations when anti-Xa activity level would be expected to be below its accuracy range in which case ACT-LR might be helpful, like to detect the residual and rebound effect of heparin after empirical neutralization of heparin following cardiopulmonary bypass. In our cardiac intensive care unit (CICU), traditional ACT had been used regularly for this purpose. We audited this use of ACT monitoring, to detect residual and rebound effect of heparin in our post-cardiac surgical patients. One hundred patients were included in the study and all of them had an ACT repeated in the CICU to monitor heparin activity after empirical neutralization of heparin in the theatre. Forty three percent of the patients had an ACT of more than 150 seconds, of whom 44% (n=19) were given additional protamine, at attending the clinician’s discretion. The median (interquartile range) four hour blood loss was 590 ml (385-755) for patients given additional protamine group, and 280 ml (180-430) for those with an ACT>150 s who did not receive additional protamine. The clinical decision to give more protamine appears to have been based on excessive mediastinal blood loss noticed soon after the admission to the CICU. In the group who received more protamine because of excessive bleeding and prolonged ACT, about 50% showed a further increase in the ACT following administration of additional protamine. This supports the notion that traditional ACT correlates poorly with the presence of free heparin,2 and suggests that the additional protamine administered in response to prolonged ACT may in fact contribute to coagulopathy. This study also supports the view that in the post-cardiac surgical cases with undue blood loss, administration of protamine and blood products should not be based on the clinical judgment alone, but algorithm based investigations for clotting dysfunction such as thromboelastography, platelet function tests, fibrinogen levels, heparin concentration and platelet count should guide clinical practice.3 It would be useful to conduct further research regarding the role of ACT-LR to detect the residual and rebound effect of heparin following cardiopulmonary bypass to increase the armamentarium of near-patient tests. References: 1. B. Tremey, B. Szekely, S. Schlumberger, D. François, N. Liu, K. Sievert, M. Fischler. Anticoagulation monitoring during vascular surgery: accuracy of the Hemochron® low range activated clotting time (ACT-LR). Br J Anaesth. 2006 Oct;97(4):453-9. Epub 2006 Jul 27. 2. Gundry SR, Drongowski RA, Klein MD, Coran AG. Postoperative bleeding in cardiovascular surgery. Does heparin rebound really exist? Am Surg 1989; 55:162-5. 3. Avidan MS, Alcock EL, Da Fonseca J, Ponte J, Desai JB, Despotis GJ, Hunt BJ. Comparison of structured use of routine laboratory tests or near-patient assessment with clinical judgement in the management of bleeding after cardiac surgery. Br J Anaesth. 2004 Feb;92(2):178-86. Conflict of Interest:None declared |
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