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Alterations of hemostasis associated with cardiopulmonary bypass: pathophysiology, prevention, diagnosis, and
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Alterations in hemostasis during cardiopulmonary bypass (CPB) are primarily due to platelet defects and hyperfibrinolysis. Preoperative assessment and specific laboratory tests are crucial for preventing and managing CPB-related hemorrhage.
Area of Science:
- Cardiovascular Surgery
- Hematology
- Anesthesiology
Background:
- Cardiopulmonary bypass (CPB) is frequently associated with alterations in hemostasis.
- Understanding these hemostatic changes is critical for patient safety during cardiac surgery.
Purpose of the Study:
- To review the available literature on hemostatic alterations during CPB.
- To identify the primary causes of bleeding complications associated with CPB.
- To recommend strategies for the prevention and management of CPB-related hemorrhage.
Main Methods:
- Literature review of studies on hemostasis and CPB.
- Analysis of the pathophysiology of altered hemostasis during CPB.
- Evaluation of diagnostic and therapeutic approaches to CPB-associated bleeding.
Main Results:
- The main causes of altered hemostasis during CPB are functional platelet defects and primary hyperfibrinolysis.
- Thrombocytopenia is not a consistent problem but can contribute to hemorrhage.
- Disseminated intravascular coagulation (DIC) is rare as a consequence of CPB alone.
- Effective preoperative assessment, including detailed patient history and specific laboratory tests (thrombin time, bleeding time), is key to preventing hemorrhage.
- Laboratory screening aids in distinguishing surgical from nonsurgical bleeding and guides treatment decisions.
Conclusions:
- Functional platelet defects and hyperfibrinolysis are the predominant causes of nonsurgical bleeding during CPB.
- Adequate preoperative evaluation and judicious use of laboratory tests can prevent most CPB-related hemorrhages.
- Prompt administration of platelet concentrates and antifibrinolytics can manage bleeding complications effectively.
Abstract:
This chapter has provided a review of available literature regarding alterations of hemostasis associated with CPB. The primary pathology of altered hemostasis during CPB appears to be two-fold: (1) a functional platelet defect of unclear etiology, which occurs in virtually all patients, and (2) a primary hyperfibino(geno)lytic defect which occurs in the majority of patients undergoing cardiopulmonary bypass. Significant thrombocytopenia does not appear to be a consistent problem, and is probably a function of perfusion technics; this may, however, be an important source of hemorrhage in some instances. Although hyperheparinemia, heparin rebound, and protamine excess have occasionally been incriminated as sources of hemorrhage during CPB, no well documented cases appear in the literature. Likewise, although DIC gained popularity in early reports of CPB hemorrahge, it appears that this syndrome rarely, if ever, arises as a consequence of CPB alone; it can be seen, however, in CPB patients who are provided a triggerin situation for DIC, such as shock, sepsis, or hemolytic transfusion reaction. It is likely that many reported alterations of hemostasis during CPB which were concluded to represent DIC actually were due to hyperfibino(geno)lysis. The key to prevention of CPB hemorrhage rests simply in obtaining an adequate preoperative workup. Of extreme importance is an adequate history with respect to bleeding tendencies in both patient and family; of equal importance is a careful history regarding antiplatelet drugs. A careful physical examination, searching for clues of a real or potential bleeding diathesis, also can often prevent catastrophic cases of CPB hemorrhage. Lastly, an adequate presurgical laboratory screen must be performed; in addition to the usual prothrombin time, partial thromboplastin time, and platelet count, a thrombin time and standardized template bleeding time must be added. The addition of these two simple modalities will insure against significant defects in fibrinogen, the fibrinolytic system, vascular function, and platelet function. When CPB hemorrhage occurs, simple laboratory screening will usually allow for a quick hemostasis evaluation. The parameters recommended in this review will distinguish between surgical and nonsurgical bleeding and should, therefore, allow for a quick decision regarding necessity for reexploration and the adequacy of hemostasis if reexploration is needed. In addition, this screen will distinguish between difficulties with heparin, protamine, and the fibrinolytic system. The vast majority of nonsurgical hemorrhages during CPB is due to a functional platlet defect, primary hyperfibrino(geno)lysis, or a combination of these. The quick administration of platelet concentrates, while awaiting laboratory evaluation, will control or significantly blunt most instances of CPB hemorrhage. If platelets fail to control bleeding, and reasonable laboratory evidence of primary hyperfibrino(geno)lysis is present, antifibrinolytics should then be used...