by Donna Castellone, MS, MT (ASCP) SH •
August 05, 2019
Coagulation is a complex process involving platelets, coagulation factors and the fibrinolytic system. Patient conditions or environmental factors may also impact bleeding and clotting formation. What happens to coagulation intraoperatively and postoperatively? Many coagulation abnormalities are known in patients before surgery. Prior to surgery things like antiplatelet medications can impede clot formation. Another contributing factor would be an inherited coagulation abnormality. A coagulopathy may occur as a result of a reduction or absence of clotting proteins or dysfunction or reduced platelets. This can lead to surgical bleeding but in critically ill patients, activation of the coagulation system from trauma, inflammation or infection may lead to thrombosis or thromboembolic complications. (1)
Hemostasis is optimal during surgery when technique controls all surgical sources of bleeding and the patient's own coagulation system functions and is capable of controlling bleeding. In this case no additional management is necessary. Satisfactory hemostasis is the goal without transfusion, and if transfusion is required the amount of blood required should try to be minimized by using measures that reduce blood loss and enhance the patients' hemostatic mechanisms. (2)
During surgery, hypothermia can inhibit clot formation because the coagulation cascade is less efficient at lower temperatures. The risk is even greater if the patient has low body weight, is older, has low blood pressure or low heart rate. (1) In trauma surgery, hemostasis is even more complicated due to what is called the lethal triad which includes hypothermia, acidosis and coagulopathy. Blood loss can also be due to consumption or dysfunction of factors and platelets.
Fibrinogen deficiencies during surgery in particular cardiopulmonary bypass, can cause bleeding since this is the precursor to the formation of fibrin. Fibrin strands are then polymerized and cross linked by FXIII. Fibrinogen also binds IIb/IIIa receptors, promoting platelet aggregation. When fibrinogen results are low, European guidelines recommend supplementation with fibrinogen concentrates. (2)
Most bleeding during cardiac surgery is related to surgery, increased age and the presence of anticoagulants. (2) To demonstrate the effect of cardiac surgery on coagulation, 66 patients were tested intraoperatively and results were compared to 45 blood donors. Testing was performed by thromboelastometric Rotem for determination of coagulation factors and levels of fibrinogen. Platelet aggregation with collagen was measured by a Chronolog aggregometer. Patients were divided into three groups. The first group of 23 patients showed a residual heparin effect in which they required protamine sulfate. The second group of 25 patients showed patients that had an increased amount of protamine sulfate. In the remaining patients, bleeding was observed with both concentration and activity of platelets being reduced. Disorders of coagulation factors in this group wasere designated as dilutional coagulopathy. (3)
Massive blood loss comprises several pathophysiologic situations including tissue injury, bleeding and transfusion of blood or blood products. The definition of massive hemorrhage is blood loss in excess of one circulating volume within a 24 hour period. Injury to the body activated several systems including the nervous system, coagulation, fibrinolytic, complement and inflammatory response systems. (4) Acute coagulopathy of trauma develops quickly after injury as a response to tissue injury and shock and is an indicator of poor prognosis. This also highlights the relationship between either a qualitative or quantitative deficiency of fibrinogen and outcomes for transfusion and mortality. (2)
Postoperatively patients develop hypercoagulability that may result in thrombotic events. A study evaluated at 51 patients undergoing different surgeries. Blood samples were taken pre and post operatively for PT, aPTT, all PT and aPTT based clotting factors, vWF and fibrinogen. Thromboelastography and multiplate electrode aggregometry were also performed. Post operatively on day 1 clotting factors II, VII, X, XI and XII were significantly decreased from baseline and factors II, X, XI and XII did not risk until day 3. On day 2 postoperatively, fibrinogen, FVIII and vWF increased with no change in the PT and aPTT. Thromboelastography demonstrated an increase in clot firmness and MEA showed on day 6 and increase in platelet aggregation. Laboratory test results confirmed that significant hypercoagulability developed in patients, but this was not reflected in screening tests or POC testing, only in specific laboratory tests. (5)
In a study of 70 orthopedic patients undergoing knee surgery, samples were collected pre, intra and postoperatively. Coagulation assays for FVII, VIII, vWF and fibrinogen were assayed as well as whole blood platelet aggregation. Platelet aggregation was found to be decreased until 1 hour post operatively and then increased significiantly. Coagulation factors decreased intraoperatively and FVII continued to decrease with an increase in FVIII, vWF and fibrinogen postoperatively. These results correlate with other studies and demonstrate how changes in these factors contribute to hypercoagulability and or bleeding risk perioperatively. (6)
Guidelines have been published by several organizations that address massive hemorrhage and transfusion management. They are as follows:
American Society of Anesthesiologists (ASA),
American College of Surgeons (ACS) Committee on Trauma,
Joint United Kingdom Blood Transfusion Services Professional Advisory Committee (JPAC).
The guidelines may differ on certain points, however there are some important and common recommendations that almost all of them share, such as the following: (7,8,9)
Establishment of a massive transfusion protocol among multidisciplinary groups within hospitals
Early recognition of the bleeding episode and achievement of hemostasis
Establishment of a threshold for triggering a massive transfusion protocol and the use of a fixed-ratio (PRBC:FFP:Plt) transfusion protocol in emergency situations; consideration of transition to goal-directed transfusion after laboratory results are obtained
Identification and early treatment of coagulation abnormality (dilutional, consumptive, or fibrinolytic coagulopathy)
Utilization of bedside point-of-care testing; consideration of viscoelastic testing for identifying coagulopathy
Detection and treatment of complications associated with massive hemorrhage and transfusion - Hypothermia, hypocalcemia, hyperkalemia, metabolic acidosis, TRALI, TACO, hemolytic transfusion reaction
Establishment of a postoperative care pathway after massive hemorrhage and massive blood transfusion
Grottke, O., Fries, D., Nascimento, B., Perioperatively acquired disorders of coagulation, Current Opinion in Anaesthesiology, April 2015 – 28:113–122.
Neeleff, DJ, Kraiss, LW., Implementing Methods to Improve Perioperative Hemostasis in the Surgical and Trauma Settings, AORN J, 2010, 92:1-15.
Lison S, Weiss G, Spannagl M, Heindl B., Postoperative changes in procoagulant factors after major surgery. Blood Coagul Fibrinolysis. 2011 Apr;22(3):190-6
Oberweis BS, Cuff G, Rosenberg A, Pardo L, Nardi MA, Guo Y, Dweck E, Marshall M, Steiger D, Stuchin S, Berger JS, Platelet aggregation and coagulation factors in orthopedic surgery. J Thromb Thrombolysis. 2014 Nov;38(4):430-8.
American Society of Anesthesiologists Task Force on Perioperative Blood Management. Practice guidelines for perioperative blood management: an updated report by the American Society of Anesthesiologists Task Force on Perioperative Blood Management*. Anesthesiology. 2015 Feb. 122 (2):241-75.