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This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Benjamin P. Bidstrup Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Bidstrup, B. P. Search for Related Content PubMed Articles by Bidstrup, B. P. Related Collections Related Article

Ann Thorac Surg 1999;67:1016-1017
© 1999 The Society of Thoracic Surgeons

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Commentary

^a Townsville General Hospital, Townsville, Queensland, Australia 4810

e-mail: bbidstrup{at}mailbox.uq.edu.au

Invited commentary

Point-of-care analytic devices must be evaluated in the clinical environment and compared with currently available methods as well as a gold standard. Anticoagulation monitoring in cardiovascular procedures lends itself to this technology, as it produces a timely result and usually requires no specialized preparation of the sample. In this study, which regrettably suffers from a lack of numbers, the authors have tested a new device, the Thrombolytic Assessment System Heparin Management Test (TAS HMT) (Pharmanetics Inc, Raleigh, NC) against the more commonly used HemoTec Automated Coagulation Timer (ACT) (Medtronic Inc, Denver, CO) and an anti-FXa heparin assay. The aim was to determine the relationship to circulating heparin levels. The TAS HMT device incorporates a novel technology for end-point detection (iron fillings and a varying magnetic field with an optical sensor) as well as data storage and downloading facilities, which detects the test being performed and uses 35 µl of blood compared with 2 mL for the ACT. Interestingly, citrated blood was used for this test which could influence the times achieved.

Several conclusions can be drawn from the data presented: (1) Baseline numbers and test results are not comparable between tests. The concept of 450 seconds, accepted for the ACT as adequate, is not applicable to the TAS HMT. (2) The slope of the ex vivo TAS HMT curve is less than that of the ACT. Large changes in heparin concentration are associated with small changes in the TAS HMT. This could lead to subtherapeutic heparin levels. (3) The claim by the manufacturers that the test is not affected by hemotocrit, temperature, or platelet count does not appear to be supported by these data. (4) The tests correlate well with lack of heparin and thus the adequacy of heparin reversal. (5) The results of the spiking experiments show a linear relationship, which is not surprising. The activation of the clotting system is dependent on not only circulating plasma factors but the endothelium and liver as well.

ACT and other tests have previously been shown to have a poor correlation to heparin levels, but rather reflect a degree of anticoagulation [1–4]. There is better correlation with heparin levels in individual patients but not between patients. This study supports these concepts.

Footnotes

¹ Dr Bidstrup has at times acted as a paid consultant (member of advisory board) to Medtronic Inc, Denver CO.

References

1. Mattox K.L., Guinn G.A., Rubio P.A., Beall A.J. Use of the activated coagulation time in intraoperative heparin reversal for cardiopulmonary operations. Ann Thorac Surg 1975;19:634-638.[Abstract/Free Full Text]
2. Culliford A., Sanford N., Starr N., et al. Lack of correlation between activated clotting time and plasma heparin during cardiopulmonary bypass. Ann Surg 1981;193:105-111.[Medline]
3. Young J.A., Kisker C.T., Doty D.B. Adequate anticoagulation during cardiopulmonary bypass determined by activated clotting time and the appearance of fibrin monomer. Ann Thorac Surg 1978;26:231-240.[Abstract/Free Full Text]
4. Despotis G.J., Summerfield A.L., Joist J.H., et al. Comparison of activated coagulation time and whole blood heparin measurements with laboratory plasma anti-Xa heparin concentration in patients having cardiac operations. J Thorac Cardiovasc Surg 1994;108:1076-1082.[Abstract/Free Full Text]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Benjamin P. Bidstrup Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Bidstrup, B. P. Search for Related Content PubMed Articles by Bidstrup, B. P. Related Collections Related Article