Clinical Aspects of Bleeding and Transfusion in Cardiac Surgery

Sammanfattning: Abstract Excessive bleeding after cardiac surgery is a serious complication that is associated with increased morbidity and mortality. The bleeding is multifactorial and influenced by both surgical factors and impaired haemostasis. It is important to identify patients with increased risk of bleeding before the operation so countermeasures can be initiated. A large proportion of cardiac surgical patients receive blood transfusions during and after surgery. Transfusion therapy can save lives, but is also associated with increased risk of morbidity and mortality, so unnecessary transfusions should be avoided. There is little knowledge about when and on what indication blood transfusions are administered, and how well treating physicians follow current guidelines. Aims: One aim was to examine the relationship between preoperative levels of fibrinogen and other coagulation factors, and their relationship to postoperative bleeding and blood transfusion. Another was to assess the effects of a structured blood conservation programme, with the objective of reducing the administration of blood transfusions in cardiac surgical patients. A third aim was to study the prevalence, volumes and indications for red blood cell transfusions in cardiac surgery patients. The final aim was to examine adherence to institutional transfusion guidelines. Materials and methods: The first study (Paper I) involved 170 patients undergoing coronary artery bypass grafting (CABG). Data on each patient´s preoperative fibrinogen plasma concentration and other haemostatic tests, and postoperative bleeding and transfusion requirements, were collected. In Paper II, the study concerned 57 CABG patients. Plasma activity of coagulation factors involved in plasma coagulation was measured before and after surgery and related to haemodilution and postoperative blood loss. In Paper III, the study involved all 2162 patients who underwent cardiac surgery at our institution during a 24-month period. Transfusion requirements and transfusion-associated costs before and after introduction of a blood conservation programme were compared. In the study described in Paper IV, timing and indications for red blood cell transfusion in 1034 cardiac surgery patients were investigated and the adherence to institutional guidelines was assessed. Results: Paper I demonstrated that preoperative plasma levels of fibrinogen correlates significantly to postoperative blood loss. Preoperative fibrinogen level was also an independent predictor of red blood cell transfusion, together with female gender and long operation time. Paper II demonstrated a marked disparity of clotting factor activity after cardiac surgery. Only plasma concentration of fibrinogen and coagulation factor XIII activity correlated to postoperative bleeding. Paper III showed that the introduction of a simple structured multifactorial blood conservation programme significantly reduces blood transfusions to cardiac surgery patients, and reduces transfusion-associated costs without compromising medical safety. The result persists for at least three years after the implementation of the programme. Paper IV demonstrated that red blood cells are often transfused for other reasons than anaemia. The adherence to institutional transfusion guidelines was low. Conclusions: Pre- and postoperative fibrinogen concentration and factor XIII activity predict postoperative bleeding volume after CABG and may be used to identify patients with increased risk of bleeding. The introduction of a structured blood conservation programme is safe and reduces the use of blood products in cardiac surgery. The adherence to transfusion guidelines among treating physicians is low.