Effects of Obesity Surgery on Blood Coagulation and Fibrinolysis: A Literature Review.

Objective:  Obesity is characterized by a disturbed hemostatic balance with increased coagulation and impaired fibrinolysis. This increases the risk of thrombosis, and the risk is lowered after obesity surgery. Over the past 25 years, several studies have contributed to understand the mechanisms behind the antithrombotic effect of obesity surgery, and this literature review summarizes the results of these studies.

Methods:  A detailed literature search on the effects of obesity surgery on the hemostatic balance was conducted.

Results:  The 25 relevant studies reviewed demonstrated that obesity surgery has favorable effects on many biomarkers of coagulation and fibrinolysis. The evidence is substantial for fibrinogen and plasminogen activator inhibitor type 1 with average reductions from 1 to 24 months after obesity surgery of 17 and 48%, respectively. For most other biomarkers, the evidence is moderate or weak with average effect sizes varying from 2% for fiber mass length ratio to 70% for prothrombin fragment 1 + 2 and with a large variation between studies. Many studies are small and of short duration, and the surgical techniques differ. Also, studies are confounded by changes in medication, comorbidity, diet, and exercise. It is unknown whether the hemostatic changes are mediated by weight loss alone or by the accompanying metabolic improvements.

Conclusion:  Despite issues of confounding, this review suggests that obesity surgery shifts the hemostatic balance in the antithrombotic direction, thereby reducing the thrombotic potential of people with obesity, but more studies are needed for most of the biomarkers.