From the Guidelines
Blood transfusions may increase the risk of deep vein thrombosis (DVT) in bariatric patients, and therefore, prophylactic measures should be emphasized to minimize this risk. Bariatric patients already have elevated DVT risk due to obesity, prolonged surgical time, reduced mobility post-surgery, and the inflammatory state associated with major surgery. Blood transfusions can further increase this risk by triggering inflammatory responses, altering blood viscosity, and potentially activating coagulation pathways. According to the most recent guidelines, including the ERAS society recommendations updated in 2021 1, and the operative management of acute abdomen after bariatric surgery guidelines from 2022 1, prophylactic measures such as early mobilization, mechanical prophylaxis with sequential compression devices, and pharmacological prophylaxis with low molecular weight heparin (such as enoxaparin 40mg daily) or unfractionated heparin (5000 units three times daily) starting before surgery and continuing until fully mobile are recommended. The dosing may need adjustment based on patient weight and kidney function, as suggested by the guidelines 1. Close monitoring for DVT symptoms (leg pain, swelling, warmth, redness) is essential, particularly in patients receiving transfusions. The transfusion-related DVT risk appears to increase with the volume of blood products administered, so following restrictive transfusion protocols (typically transfusing only when hemoglobin falls below 7-8 g/dL) may help minimize this risk.
Some key points to consider in the management of bariatric patients at risk of DVT include:
- The use of low-molecular-weight heparin for venous thromboembolism prophylaxis, with dose adjustment based on patient weight, thrombotic risk, and creatinine clearance 1
- The continuation of venous thromboembolism prophylaxis at least 4 weeks after discharge 1
- The monitoring of anti-Xa levels to adjust low-molecular-weight heparin dose, particularly in high-risk patients 1
- The use of mechanical prophylaxis in patients where pharmacologic venous thromboembolism prophylaxis is contraindicated 1
It is also important to note that the risk factors for VTE in bariatric patients are not well established, but the Caprini risk assessment model can be used to identify patients at high risk of VTE 1. However, the most recent and highest quality study on this topic is the ERAS society recommendations updated in 2021 1, which provides guidance on the prevention of thromboembolic complications in bariatric surgery patients.
From the Research
Risk of DVT in Bariatric Patients
- The risk of deep vein thrombosis (DVT) in bariatric patients is a significant concern, with studies indicating that the incidence of DVT can range from 0.2% to 0.64% after bariatric surgery 2, 3.
- Several factors can contribute to the increased risk of DVT in bariatric patients, including:
- History of DVT: Patients with a history of DVT are at higher risk of developing DVT after bariatric surgery (OR 6.2, CI 4.44-8.45, p < 0.001) 3.
- Transfusion: Blood transfusion is a significant risk factor for DVT, with an odds ratio of 4.2 (CI 2.48-6.63, p < 0.001) 3 and 4.7 (95% CI 2.9-7.9, p < 0.0001) 4.
- Operative length: Prolonged operative length is associated with a higher risk of DVT (OR 1.1, CI 1.01-1.30, p = 0.04) 3.
- The use of thromboprophylaxis, such as low-dose heparin or low molecular weight heparins, can help reduce the risk of DVT in bariatric patients 5, 6.
Blood Transfusions and DVT Risk
- Blood transfusions can increase the risk of DVT in bariatric patients, with studies indicating that transfusion is a significant risk factor for DVT (OR 4.2, CI 2.48-6.63, p < 0.001) 3 and (OR 4.7,95% CI 2.9-7.9, p < 0.0001) 4.
- The exact mechanism by which blood transfusions increase the risk of DVT is not fully understood, but it may be related to the potential for a hypercoagulable state induced by the transfusion 4.
- Bariatric surgeons should carefully consider the risks and benefits of blood transfusions in patients undergoing bariatric surgery, and take steps to minimize the risk of DVT, such as using thromboprophylaxis and screening for DVT 4, 3.