The Egyptian Journal of Cardiothoracic Anesthesia

CASE REPORT
Year
: 2018  |  Volume : 12  |  Issue : 3  |  Page : 42--44

Intraoperative thromboelastographic assessment of platelet function in a patient with low platelet count and high-mean platelet volume requiring cardiac surgery


Francesco Del Sindaco, Daniel Rajeev, Sandra Faloye, Lisa Vipond 
 Department of Anaesthesia, Royal Brompton Hospital, Sydney Street, London, UK

Correspondence Address:
Francesco Del Sindaco
Royal Brompton Hospital, Sydney Street, London, SW3 6NP
UK

Abstract

An 80-year-old patient with low platelet count was admitted in our institution for aortic valve replacement and a coronary artery bypass graft. Because of thrombocytopenia, a mean platelet volume has been assessed, showing a value above the range. Two pools of platelets were booked but not transfused, neither in the theater nor during the postoperative period. A thromboelastographic assessment at the end of the cardiopulmonary bypass showed a normal overall platelet function, and no clinical issues (diffuse bleeding after protamine and/or oozing from the drain above the range, in the postoperative period) were noticed. The authors point out the importance of thromboelastographic or thromboelastometric assessments in patients with isolated thrombocytopenia and high-mean platelet volume to contribute to reduce the risk of inappropriate transfusions.



How to cite this article:
Sindaco FD, Rajeev D, Faloye S, Vipond L. Intraoperative thromboelastographic assessment of platelet function in a patient with low platelet count and high-mean platelet volume requiring cardiac surgery.Egypt J Cardiothorac Anesth 2018;12:42-44


How to cite this URL:
Sindaco FD, Rajeev D, Faloye S, Vipond L. Intraoperative thromboelastographic assessment of platelet function in a patient with low platelet count and high-mean platelet volume requiring cardiac surgery. Egypt J Cardiothorac Anesth [serial online] 2018 [cited 2019 Oct 13 ];12:42-44
Available from: http://www.ejca.eg.net/text.asp?2018/12/3/42/258994


Full Text



 Introduction



The correlation between low platelet count and high-mean platelet volume (MPV), in some patients, is well known and studied [1],[2],[3],[4]. A larger MPV can often counteract a lower number of platelets, resulting in their normal global activity in the hemostatic process. Automatic platelet count devices, for technical reasons, sometimes are unable to detect such large cells and to recognize them as platelets, leading to a further underestimation of their number [5].

In cardiac surgery, in such cases, the main questions are as follows:Will the larger volume be able to compensate for the low number of platelets?Should we have to book platelets to have them promptly available and should we decide about transfusion on the basis of clinical assessment supported by point of care tests?Should we transfuse the patients in anyway?Should we postpone the surgery?

Unfortunately, MPV is often not provided, on a routine basis, by some laboratories, making the risk of superfluous platelet transfusions or procedure cancellation more probable. A reliable assessment of platelets’ overall function is desirable to contribute to avoid these potential risks.

Case report

An 80-year-old man was scheduled for aortic valve replacement owing to severe aortic valve stenosis and coronary artery bypass graft for a critical stenosis of the right coronary artery. The preoperative platelet count was 84×109/l, which is below our institution threshold for adult cardiac surgery (100 000×109/l). Because of this, a MPV assessment was performed, showing a value above the normal range (6.8–10.1 fl). The hematological advice, therefore, was to book two pools of platelets, to be transfused in case of diffuse bleeding due not to other detected reasons. As the patient was on regular aspirin, suspended 7 days before the surgery, a multiplate test (Multiplate Analyzer; Roche Diagnostics International Ltd, Rotkreuz, Switzerland) was requested to rule out any residual effect of the drug. Thromboxane A2 receptors were not blocked by aspirin: ASPI test 115 U (range: 71–115 U).

Before starting the CPB, 3000 mg of intravenous tranexamic acid as a bolus dose and 25 000 units of heparin intravenously were administered.

During the rewarming time of the CPB, at 35°C, a thromboelastogram (TEG; Hemoscope Corporation, Niles, Illinois, USA) with kaolin and heparinase, and with abciximab and heparinase (functional fibrinogen), and a full blood count (Horiba ABX Micros ES 60; HORIBA Ltd, Kyoto, Japan) were performed.

The kaolin with heparinase and functional fibrinogen TEG diagrams are shown in the [Figure 1] and [Figure 2], respectively. As can be seen, all the parameters were in range, particularly the Heparinase TEG Maximum Amplitude (MA), which depends on fibrinogen, platelet number and factor XIII (58.3 mm; range: 54–72 mm). The platelet count was 55×109/l, and the MPV 10.6 fl. The blood cell counter device detected the presence of schistocytes on the counting zone of platelets, and abnormal number of cells in comparison with the lymphocytes in the 30–60 fl zone, probably owing to platelet aggregation. The CPB lasted 120 min, and the cross-clamping time was 85 min.{Figure 1}{Figure 2}

In the theater, after heparin full reversal, the patient did not show any clinical sign of coagulopathy, and supported by the results of the point of care tests performed at the end of the CPB, no platelets were transfused. During the postoperative period, the bleeding from the drains was below the value considered critical in our institution (250 ml/h and/or 50 ml/10 min) and neither platelets nor other blood products were transfused.

The postoperative course was uneventful, and the patient was discharged on the fifth postoperative day.

 Discussion



This case suggests an easy assessment of the overall hemostatic function of platelets in case of low cell count and high MPV. Despite a significant low platelet count, a normal MA in the thromboelastographic assessment could suggest an overall normal function of the platelets. This indicates that platelets, activated by thrombin in the TEG cuvette, although of lower number, could interact properly with other factors to achieve a normal clot firmness. TEG was not designed to assess platelet function (the available tests to assess, using different techniques, platelets function through viscoelastic essays need further studies to be fully validated) but just their number [6]. Nevertheless, in this case, the MA of the TEG could suggest us the overall platelet activity in the hemostatic process. The cell counter device alarms could point to the existence of large platelets, but results were not conclusive. Based on the clinical observations and thanks to the TEG results, the patient did not receive any platelets and/or any other blood product during the entire perioperative period. A rewarming time or, better, a basal assessment can contribute in reducing inappropriate transfusions, and therefore, to lower the costs of the operations and to reduce the risks of transfusion-related complications, like transfusion-related acute lung injury or infection transmission, not negligible in case of room temperature-stored products such as platelets [7],[8],[9].In conclusion, in case of isolated thrombocytopenia with high MPV, thromboelastography and thromboelastometry, are useful and easy tests to assess the overall platelets function and help to reduce the risks of transfusion-related cost and complications.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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