Postoperative bleeding is one of the most common complications after cardiac surgery, especially in open heart surgery. In this type of surgery, surgeons must resort to cardiopulmonary bypass, an extracorporeal circuit made up of tubes and machines that reproduce the function of the heart and lungs. This allows them to work inside the heart while it remains still and bloodless. Despite its undeniable usefulness, the circulation of blood outside the body affects the number and function of the components responsible for coagulation, the platelets. As such, to prevent or compensate for bleeding, patients often require blood transfusions, which not only increases their risk of death but also entails considerable healthcare costs.
With the intention of finding molecular signatures that could inform prognosis, researchers at the Gulbenkian Institute of Science (IGC) studied blood samples from 33 patients undergoing heart valve replacement surgery at the hospital’s cardiothoracic surgery department of Santa Maria, in Lisbon. Samples were drawn before and 6 and 24 hours after surgery and compared between patients with and without postoperative bleeding.
Changes in the levels of fats belonging to the omega-6 family in the blood of these patients caught the attention of the researchers. Interestingly, patients with low levels of this fat in their blood before surgery lost more blood and needed almost twice as many postoperative transfusions. Although these fats were known to regulate the aggregation of platelets to form clots, they had never been linked to the risk of bleeding.
We were very excited to find this signature that could be mechanistically related to the risk of bleeding after cardiac surgery and possibly decrease it.”
Tiago Velho, co-author of the study, cardiothoracic specialist at the Hospital de Santa Maria and PhD student at the IGC
Postoperative bleeding was also higher in patients whose omega-6 levels decreased between the preoperative and postoperative time points. But what causes this alteration? The authors explain that this is another example of the complex crosstalk between inflammation and coagulation related to surgery. An important inflammatory mediator, known to increase the number and stimulate the function of platelets, appears to be related to the variability of blood fat in patients. In particular, this proinflammatory mediator appears to be decreased in patients with major bleeding. As such, inflammation could be the cause of alterations in this fat and, consequently, of platelet dysfunction after cardiac surgery.
In summary, this study shows that changes in the levels of fats of the omega-6 family, associated with inflammation, are characteristic of cardiac surgery with cardiopulmonary bypass” looking at the number of platelets”, explains Luís Moita, researcher head of the IGC’s Innate Immunity and Inflammation group, and also a physician in training. Supplementation with this fat before surgery could be a safe and inexpensive option to ensure the normal functioning of these blood components. Researchers have already are planning a study “to evaluate the effectiveness of this strategy in reducing bleeding and transfusions after surgery.”
Source:
Gulbenkian Institute of Science (IGC)
Journal reference:
Velho, TR, et al. (2022) Role of Omega-6 Fatty Acid Metabolism in Postoperative Bleeding Risk of Cardiac Surgery. Critical care scans. doi.org/10.1097/CCE.0000000000000763.