Interact CardioVasc Thorac Surg 2005;4:456-463. doi:10.1510/icvts.2005.115154
© 2005 European Association of Cardio-Thoracic Surgery
Best evidence topic - Cardiac general |
Can the use of thromboelastography predict and decrease bleeding and blood and blood product requirements in adult patients undergoing cardiac surgery?
Andrew Ronalda and
Joel Dunningb,*
a Department of Cardiac Anaesthesia, Aberdeen Royal Infirmary, Aberdeen, UK
b Department of Cardiothoracic Surgery, James Cook University Hospital, Middlesbrough, UK
Received 20 June 2005;
accepted 22 June 2005
*Corresponding author. Tel./Fax: +44 7801548122.
E-mail address: joeldunning{at}doctors.org.uk. (J. Dunning).
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Abstract
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A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether use of thromboelastography could predict and decrease bleeding and blood and blood product requirements in adult patients undergoing cardiac surgery. Altogether 170 papers were identified using the reported search strategy of which 14 represented the best evidence on the topic. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses were tabulated. We conclude that thromboelastography may be useful in predicting patients who are likely to bleed postoperatively but more importantly, it can guide transfusion therapy algorithms in the bleeding cardiac surgical patient resulting in significant decreases in blood and blood component transfusion requirements. However, the technique remains unvalidated in the eyes of many haematologists and further large studies involving them are required to fully validate its use and to define the ‘ideal’ treatment algorithm.
Key Words: Evidence-based medicine; Thromboelastography; Blood products; Bleeding
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1. Introduction
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A best evidence topic was constructed according to a structured protocol. This protocol is fully described in the ICVTS [1].
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2. Three part question
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In [adult patients undergoing cardiac surgery], does [Thromboelastography] predict or decrease [bleeding and blood product requirements].
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3. Clinical scenario
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You start work in a new unit which routinely uses thromboelastography to manage coagulopathy and guide treatment with blood component therapy following surgery. As you have no experience of the technique you decide to review the literature to identify whether the technique is actually beneficial in decreasing exposure to allogeneic blood and blood component therapy.
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4. Search strategy
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Medline 1966 to June 2005 using the OVID interface and EMBASE 1980 to June 2005.
[CABG.mp OR exp Thoracic Surgery/OR Coronary art$ bypass.mp OR Cardiopulmonary bypass.mp OR exp Cardiovascular Surgical Procedures/OR exp Thoracic Surgical Procedures/OR exp Coronary Artery Bypass/] AND [thromboelastography.mp. OR exp Thrombelastography/OR TEG.mp] AND [bleeding.mp OR platelets.mp OR exp Blood Platelets/OR blood transfusion.mp OR exp Blood Transfusion/OR fresh frozen plasma.mp OR exp Plasma/OR exp Blood Platelets/OR exp Blood Component Transfusion/OR exp Platelet Transfusion/OR exp Blood Transfusion/OR blood component therapy.mp OR exp Erythrocyte Transfusion/].
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5. Search outcome
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A total of 170 papers were identified using the reported search of which 14 represented the best evidence on the subject. These studies are summarised below (Table 1).
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6. Discussion
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Thromboelastography (TEG) is a point-of-care whole blood coagulation monitor which provides information on specific aspects of coagulation including time to production of initial fibrin strands (R-time), time to develop clot (R-time, K-time), rate of fibrin build-up and cross linking ( -angle), maximum clot strength (maximum amplitude–bMA) and measures of fibrinolysis (decreasing amplitude post-MA).
Abnormal TEG data may predict patients who will bleed. Spiess [2] found that TEG correlated well with ACT and coagulation profiles and whilst no coagulation test was consistently abnormal the TEG was the most accurate predictor of bleeding.
Ereth [4] studied a ‘Platelet-activated clotting test’ (PACT HemoSTATUS), ACT and clotting studies, and TEG. Whilst PACT sensitivity and specificity was comparable to conventional coagulation tests in predicting blood loss, TEG was more predictive at both blood loss levels. Essell [5] found that whilst the bleeding time and platelet count had sensitivities similar to the TEG, TEG specificity was greater. In addition, they suggested that patients with an abnormal TEG were at increased risk of bleeding but that excessive bleeding in the face of a normal TEG implied surgical bleeding and FFP and platelets should not simply be used empirically. Ti [7] found moderate correlation between TEG parameters, total blood loss and requirements for FFP and/or platelets in their group of ‘bleeders’.
In contrast, other studies did not find the TEG to be a useful predictor of blood loss. Nuttall [8] reported that TEG values had a low sensitivity and specificity in predicting ‘bleeders’. Dorman [9] compared preoperative coagulation screens to ACTs and TEGs as predictors of blood loss but found no significant relationship between any TEG variable and losses.
A number of studies have used the TEG to guide transfusion management. Avidan [10] Compared TEG to a Laboratory based algorithm. They concluded that whilst blood and blood product usage was significantly more in the laboratory group, there was no statistically significant difference between the study groups. Spiess [11] analysed 1079 patients before and after the introduction of TEG as part of an overall transfusion management strategy. They identified significant changes in their practice with decreased usage of all blood and blood component therapies with the exception of cryoprecipitate. Their re-exploration rate also fell significantly. However, this study probably reflects the effects of education and co-operative behaviour in monitoring changes rather than a true experimental difference between groups.
Two randomised controlled trials have been performed. Shore-Lesserson [13] compared ‘TEG-based’ and ‘conventional’ protocols to manage postoperative bleeding. Whilst there was no significant difference in mediastinal tube drainage between the groups, blood and blood component therapy was significantly less in the ‘TEG’ than in the ‘conventional group’. However, the ‘TEG protocol’ did have more options than the conventional protocol and was also partly dependent on laboratory tests. In addition, blood products were ordered on the basis of a TEG taken at rewarm on cardiopulmonary bypass and given in the presence of continued bleeding following protamine, whereas, the conventional group required post-protamine tests to dictate intervention. This inevitably meant earlier intervention in the TEG group. Royston [14] studied 60 patients who had undergone complex surgery comparing their actual blood/blood product use to a ‘predicted usage’ derived from a TEG-based algorithm. ‘Predicted’ blood/blood component transfusion was significantly less than ‘actual’ transfusion. They subsequently used this algorithm comparing it to conventional management in a further 60 patients. Again they demonstrated significantly less blood/blood component usage in the TEG-based group compared to the conventional ‘clinician-directed’ group with no excessive mediastinal bleeding. However, this study was designed to identify TEG-evidence of coagulation before physical evidence of microvascular bleeding and the authors acknowledge the fact that their protocol allowed much earlier intervention in the active than in the control limb.
A recent review by Samama [15] has raised concerns that thromboelastography remains an unvalidated technique which fails to achieve the stringent standard quality-control procedures essential in laboratory-based tests, citing absence of a formal standard operating procedure taking into account factors such as gender and pregnancy differences, stability of blood samples, and sampling site. There is also no standardised technique and multiple modifications exist including plain versus heparinase samples; celite, kaolin or tissue factor activation; abximimib (Reopro) modified; modified multi-channel; and ROTEG have been described. Several studies acknowledge that TEG facilitates earlier intervention than standard coagulation tests [10,13,14] thus making true comparisons difficult. Samama et al. conclude their review by suggesting that extended collaborative studies involving haematologists are required to further evaluate and validate thromboelastography [15].
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7. Clinical bottom line
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Thromboelastography can be used to predict bleeding in cardiac surgery, but it can also be used to guide transfusion therapy during postoperative bleeding using appropriate treatment algorithms where its use has been associated with significant decreases in blood and blood component transfusion. However, thromboelastography remains unvalidated compared to other laboratory-based routine coagulation studies and further large controlled studies involving haematology input are required to confirm that its use can be extrapolated to all types of cardiac surgery and also to define the ‘ideal’ treatment algorithm.
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References
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- Dunning J, Prendergast B, Mackway-Jones K. Towards evidence-based medicine in cardiothoracic surgery: best BETS. Interactive CardioVasc Thorac Surg 2003;2:405–409.[Abstract/Free Full Text]
- Spiess BD, Tuman KJ, McCarthy RJ, DeLaria GA, Schillo R, Ivankovich AD. Thromboelastography as an indicator of post-cardiopulmonary bypass coagulopathies. J Clin Monito 1987;3:25–30.
- Ostrowsky J, Foes J, Warchol M, Tsarovsky G, Blay J. Plateletworks platelet function test compared to the thromboelastograph for prediction of postoperative outcomes. J Extra-Corp Technol 2004;36:149–152.
- Ereth MH, Nuttall GA, Klindworth JT, MacVeigh I, Santrach PJ, Orszulak TA, Harmsen WS, Oliver WC Jr. Does the platelet-activated clotting test (HemoSTATUS) predict blood loss and platelet dysfunction associated with cardiopulmonary bypass? Anesth Analg 1997;85:259–264.[Abstract]
- Essell JH, Martin TJ, Salinas J, Thompson JM, Smith VC. Comparison of thromboelastography to bleeding time and standard coagulation tests in patients after cardiopulmonary bypass. J Cardiothorac Vasc Anesth 1993;7:410–415.[CrossRef][Medline]
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- Ti LK, Cheong KF, Chen FG. Prediction of excessive bleeding after coronary artery bypass graft surgery: the influence of timing and heparinase on thromboelastography. J Cardiothorac Vasc Anesth 2002;16:545–550.[Medline]
- Nuttall GA, Oliver WC, Ereth MH, Santrach PJ. Coagulation tests predict bleeding after cardiopulmonary bypass. J Cardiothorac Vasc Anesth 1997;11:815–823.[CrossRef][Medline]
- Dorman BH, Spinale FG, Bailey MK, Kratz JM, Roy RC. Identification of patients at risk for excessive blood loss during coronary artery bypass surgery: thromboelastography vs. coagulation screen. Anesth Analg 1993;76:694–700.[Abstract/Free Full Text]
- 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;92:178–186.[Abstract/Free Full Text]
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- Koster A, Kukucka M, Fischer T, Hetzer R, Kuppe H. Evaluation of post-cardiopulmonary bypass coagulation disorders by differential diagnosis with a multichannel modified thromboelastogram: a pilot investigation. J Extra-Corp Technol 2001;33:153–158.
- Shore-Lesserson L, Manspeizer HE, DePerio M, Francis S, Vela-Cantos F, Ergin MA. Thromboelastography-guided transfusion algorithm reduces transfusions in complex cardiac surgery. Anesth Analg 1999;88:312–319.[Abstract/Free Full Text]
- Royston D, von Kier S. Reduced haemostatic factor transfusion using heparinase-modified thrombelastography during cardiopulmonary bypass. Br J Anaesth 2001;86:575–578.[Abstract/Free Full Text]
- Samama CM, Ozier Y. Near-patient testing of haemostasis in the operating theatre: An approach to appropriate use of blood in surgery. Vox Sanguinis 2003;84:251–255.[Medline]
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Abstract
1. Introduction