Thesis defence in the University of Oulu

Doctoral Candidate

Licentiate of Medicine Mari Pohjola

Faculty and research unit

University of Oulu Graduate School, Faculty of Medicine, Research group of Surgery, Anesthesiology and Intensive Care Medicine

Field of study

Anesthesiology and Intensive Care Medicine

Date and time of the thesis defence

2.10.2020 12:00

Place of the thesis defence

Oulu University Hospital Auditorium 3

Topic of the dissertation

Thromboelastography for coagulation monitoring in obesity and cytoreductive surgery.

Opponent

Docent Raili Suojaranta, University of Helsinki

Custos

Professor Tero Ala-Kokko, University of Oulu

Thromboelastography for coagulation monitoring in obesity and cytoreductive surgery

Thromboelastography (TEG) is a device that measures blood clotting and can be used to assess the risk of venous thrombosis and pulmonary embolism in surgical patients.

Venous thromboembolism (VTE) and pulmonary embolism are rare but unfortunate complications in surgical patients that prolong recovery, increase the cost of surgical treatment, and - in some cases - lead to death after successful surgery. Significant obesity is a risk factor for venous thrombosis and pulmonary embolism, as is active cancer and extensive cancer surgery. During surgery, venous thrombosis can be prevented with compression stockings, sequential compression devices, and anticoagulant medication. However, these are not always sufficient. Anticoagulant medication will also increase the probability for bleeding after surgery. The risk of venous thrombosis can be assessed using a variety of risk-scoring methods and blood tests, but the accuracy of these in predicting thrombosis is modest.

TEG can be used to detect a tendency for excessive clotting, which contributes to venous thrombosis and pulmonary embolism. The purpose of this study was to investigate whether obesity surgery and subsequent weight loss affect patients' risk for VTE and to determine the extent to which cancer surgery and associated intra-abdominal chemotherapy affect blood coagulation during and after surgery.

A tendency to excessive blood clotting was observed in patients undergoing obesity surgery. Within six months after surgery, the patients had lost approximately 20 kg of weight and their obesity-related inflammatory condition had alleviated. An excessive tendency for blood to clot was still observed, however, in both TEG and traditional blood clotting tests. As a conclusion, patients who have undergone obesity surgery are still at increased risk for venous thrombosis and pulmonary embolism 6 months after surgery.

Excessive coagulation was also observed in patients undergoing major abdominal cancer surgery. At about two weeks after discharge this was maximal as measured by both TEG and conventional blood coagulation tests. At the 3-month control, coagulation had normalized in most patients, although this was still noticeable in some. One patient suffered pulmonary embolism during the follow-up period. As a conclusion, anticoagulant medication should be continued for several weeks after surgery. TEG can also be used to detect patients at particularly high risk for whom dose escalation should be considered.

All in all, TEG can be used to detect an excessive tendency for blood to clot and to target anticoagulant medication to patients at special risk. Despite TEG findings, only one patient suffered pulmonary embolism, therefore TEGs ability to predict venous thromboembolisms is also limited.

Dissertation

Last updated: 14.9.2020