Intra-operative transfusion management: the usefulness of point-of-care coagulation monitoring

Dear Sir,

We have read with interest the paper by Liumbruno et al., which deals with both the rationale and major concerns of transfusion practice in elective surgery¹. As anaesthesiologists we particularly appreciated the reported multifaceted recommendations on the intra-operative transfusion approach. Most of the time anaesthesiologists are fully responsible for the decision to transfuse as well as for the transfusion itself. Clear and easy-to-use guidelines for blood component therapy are, therefore, very welcome.

Well-examined and detailed recommendations are made on the evaluation and monitoring of anaemia, blood loss, intra-operative blood salvage, transfusion threshold for red blood cells, platelets, fresh-frozen plasma, fluids, cryoprecipitate, fibrinogen, antithrombin, as well as appropriate and inappropriate indications. However, among the numerous suggestions made, the need for point-of-care coagulation testing in cases of persistent bleeding is not mentioned. Strict, bedside monitoring of haemostasis is, in fact, essential in patients with a complex and rapidly changing coagulation profile. In addition to the mentioned therapeutic interventions to control and rationalise blood and blood product usage, we believe that thromboelastography, which provides rapid and reliable information on coagulation deficits, deserves attention.

Thromboelastography is now widely used as a near-site monitor of haemostasis, and, even though it remains relatively unvalidated compared with other laboratory-based routine coagulation studies, it plays a leading role among anaesthesiologists in the management of difficult haemostasis².

Conventional coagulation screens (prothrombin time, partial thromboplastin time, platelet count and fibrinogen concentrations) are frequently inadequate for the purpose of intra-operative monitoring of unpredictable coagulation. During massive haemorrhage conventional laboratory tests require too much time, and if significant bleeding continues, when the laboratory data are finally available the patient’s coagulation profile may be completely different. In these circumstances anaesthesiologists should be offered a point-of-care clotting analyser capable of providing reliable near real-time results.

Conventional Thromboelastography (TEG) provides information starting with the formation of the fibrin-platelet clot and continues to generate data as clotting continues through to eventual clot lysis or retraction. TEG assists in the differential diagnosis of coagulopathy, differentiates surgical from non-surgical bleeding and helps to indicate the most adequate blood transfusion products and pharmacological agents to achieve optimal biological haemostasis. Although it cannot identify the individual coagulation factors (e.g. factors VIII, IX and X), inhibitors (e.g. antithrombin, protein C and protein S) or activators (e.g. thromboxane A2 and ADP), the time, rate, strength and stability of the clot indicate whether the patient has a normal, hypocoagulable or hypercoagulable coagulation profile. Furthermore, the potential interference between blood and blood components and intravenous crystalloids and/or colloids are also detected by TEG.

Cardiovascular, urological, obstetric and trauma surgery still requires a significant amount of blood components and is very demanding on the local blood bank. In various studies blood usage has been demonstrated to be significantly less when based on TEG information than when conventional “clinician-directed” management is used^2,3. Using thromboelastography variables has led to a substantial decrease in blood component transfusion in many surgical settings. During liver transplantation the amount of fresh-frozen plasma administered was significantly reduced with the use of TEG-guided criteria for transfusion⁴. In cardiac surgery TEG may be useful for predicting patients who are likely to bleed post-operatively and, more importantly, it can guide transfusion therapy algorithms in order to prevent bleeding⁵.

TEG, rotative thromboelastometry (ROTEM^®), and Sonoclot^® coagulation analysers provide global information on the dynamics of clot development, stabilisation and dissolution which reflect in vivo haemostasis. Another advantage of point-of-care coagulation monitoring is further reducing empirical transfusions in high-risk patients already being treated prophylactically with various drugs (e.g. antiplatelet agents, low molecular weight heparin, antifibrinolytics).

The results of TEG/ROTEM^® should, however, be carefully interpreted and correlated to the patient’s clinical condition. This is due to a number of limitations of these monitoring systems, such as the measurement of haemostasis under static conditions in vitro, the depiction of clot development as a whole blood analysis of the coagulation status, and their inability to distinguish multiple coagulation deficiencies easily. No single TEG/ROTEM^® parameter correlates directly with laboratory coagulation tests but, when combined, they enable identification of specific component deficiencies.

Bed-side coagulation monitoring systems are still underused in the operating room, despite their recognised benefits. Costs, untrained or under-trained physicians, poorly controlled quality checking and limited interest in blood-saving are among the principal causes of their relatively uncommon use.

Future improvements in point-of-care coagulation analysers, with easier handling of blood samples, full automation, simultaneous testing with multiple activators, integrated analysis software and increased comparability with laboratory values will provide more reliable results and promote the introduction of these devices into clinical practice.

As reported by Afshari et al.³, there is still a lack of evidence that TEG or ROTEM^® improves morbidity or mortality in patients with severe blood loss; however, application of a TEG- or ROTEM^®-guided transfusion strategy was found to have a statistically significant effect on predefined outcomes such as reduced bleeding and reduced number of patients requiring transfusion of both platelets and fresh-frozen plasma.

In conclusion, adopting a TEG- or ROTEM^®-based algorithm in the routine management of patients with haemostatic abnormality, and in those with surgery or transfusion-related coagulopathy may help to improve clinical outcome and reduce the potential risks of transfusion-related complications. Supporting ongoing transfusion therapy with the aid of visco-elastic whole blood assays proves advantageous in maintaining normal haemostatic competence until surgical haemostasis is achieved. This strategy may lead to a diminished transfusion threshold compared to that indicated by the prothrombin time/International Normalised Ratio and thus reduce the need for allogeneic blood products.