Hematologic Problems in the Surgical Patient: Bleeding and Thrombosis

History

Preoperative evaluation of hemostatic risk begins with a carefully taken history (see Chapter 126 ). Particular attention should be directed at specific bleeding symptoms and any history of bleeding associated with surgical procedures, including circumcision, tonsillectomy, and dental extractions. For women, it is important to inquire about a history of menorrhagia or excessive bleeding associated with childbirth. Detailed family history and record of medication use, including non-prescription medications, should be obtained.

Obtaining an adequate bleeding history may be complicated by the fact that even in the absence of hemostatic defects, many people consider their bleeding to be excessive. In surveys, healthy individuals frequently report excessive nosebleeds (5% to 39%), gingival bleeding (7% to 51%), easy bruising (12% to 24%), menorrhagia (23% to 44%), postpartum bleeding (6% to 23%), and bleeding following dental extraction (up to 13%) and tonsillectomy (up to 11%). The combination of objective evidence and a constellation of symptoms is more helpful than either alone in suggesting the presence and etiology of an underlying bleeding disorder.

Coagulation Testing

The need for routine coagulation testing before surgical or invasive procedures remains controversial. Those in favor of testing point to the asymptomatic nature of some hemostatic abnormalities that may cause surgical bleeding and the occasional failure to obtain a detailed history. Given the variety of potential hemostatic defects; however, no simple screening system will identify all patients at increased risk for bleeding. Those against routine laboratory testing point to retrospective studies indicating that they rarely detect unexpected bleeding disorders and emphasize the problems associated with the evaluation of false-positive results. A retrospective review of the value of preoperative determination of the platelet count, prothrombin time (PT), and activated partial thromboplastin time (aPTT) in 828 patients undergoing major noncardiac surgery found that only 2% had abnormal results, and most were expected based on history and physical examination. Furthermore, abnormal laboratory test results and intraoperative blood loss or postoperative bleeding complications were not related (see Chapter 126 ). A number of prospective studies have also concluded that routine laboratory screening tests in asymptomatic patients are not predictive of perioperative or postoperative bleeding. Thus, in the absence of historical risk factors or physical examination findings suggestive of an underlying bleeding tendency, the likelihood of an unsuspected, clinically significant, congenital or acquired coagulopathy is low enough that routine laboratory screening is not warranted, particularly for those undergoing low-risk procedures. The British Committee for Standards in Haematology issued guidelines reiterating this position: indiscriminate coagulation testing before surgical or invasive procedures is a poor predictor of bleeding risk, and is not recommended in the absence of a positive personal or family bleeding history.

There are several reasons why routine coagulation tests such as the PT/international normalised ratio (INR) and aPTT may be poorly predictive of underlying coagulopathy and bleeding risk. First, these tests were designed to measure time to clot formation in artificial in vitro assays and do not reliably depict global hemostasis in vivo (see Liver Disease section). More importantly, the PT/INR and aPTT may be insensitive to mild but clinically relevant bleeding disorders such as von Willebrand disease or mild hemophilia (see Chapter 133, Chapter 134 ). Conversely, they may detect conditions such as factor XII deficiency or a lupus anticoagulant that do not increase the risk for bleeding.

Notwithstanding the controversy about the value of preoperative laboratory screening (see Chapter 127 ), it is reasonable to personalize the approach to preoperative evaluation depending on the hemostatic risk of the proposed surgery or invasive procedure ( Tables 155.1 and 155.2 ). A hemostatic history should always be obtained, and no laboratory testing is required in patients undergoing procedures at low risk for bleeding. For procedures associated with a high risk of bleeding, screening could include a PT/INR, aPTT, and determination of the platelet count. In practice, hematologists are rarely consulted for routine screening because surgeons have adopted approaches based on their own training and local practice patterns. Instead, consultation is sought because of a history suggestive of a bleeding disorder or because an abnormal test result is found on screening. If a referral is requested because of an abnormal screening test, the abnormality needs to be identified using a focused history and physical exam, and appropriate laboratory testing to further evaluate the issue.

Desmopressin

Desmopressin (1-deamino-8- d -arginine vasopressin, or DDAVP) is a synthetic analogue of the antidiuretic hormone arginine vasopressin. Intravenous, subcutaneous, or intranasal administration of DDAVP results in transient increases in plasma concentrations of factor VIII and von Willebrand factor as a result of their release from vascular endothelium. Peak levels (typically two to four times baseline) are achieved 30 to 60 minutes after intravenous and 60 to 90 minutes after subcutaneous or intranasal administration (see Chapter 133, Chapter 134 ). Doses may be repeated at intervals of 12 to 24 hours, but tachyphylaxis may occur after three or four doses, limiting further usefulness of DDAVP. The expression of glycoprotein Ib (GPIb) and GPIIb/IIIa on the platelet membrane is also enhanced after DDAVP administration. DDAVP is the treatment of choice for patients with mild hemophilia A or type 1 von Willebrand disease who require low-risk surgical procedures (see Chapters 133 and 134 ). Moderate- or high-risk procedures usually require administration of clotting factor concentrates. DDAVP may also be useful for patients with congenital or acquired platelet function disorders.

DDAVP does not reduce blood loss or transfusion requirements after cardiopulmonary bypass surgery. Worrisome also is the fact that a metanalysis shows a 2.4-fold increase in perioperative myocardial infarction in cardiac surgery patients treated with DDAVP. Thus, the routine use of DDAVP in cardiac, orthopedic, or other elective surgical procedures is not recommended. A more recent metanalysis of 38 randomized placebo-controlled trials that included nearly 2500 surgical patients found that DDAVP slightly reduced blood loss (by approximately 80 mL) and transfusion requirements (by approximately 0.3 units) but did not reduce the proportion of patients receiving transfusions. Although the authors acknowledged that the clinical impact of the reduced transfusion requirement is questionable, they felt this could not be ignored because of the low cost of DDAVP. The incidence of thromboembolic events in the DDAVP and placebo groups was similar (5.4% and 4.6%, respectively), but they pointed out that identification of harm from DDAVP is limited by study design, and that the safety concerns remain unresolved. Nonetheless, certain subgroups of patients, such as those with platelet dysfunction, may derive benefit. Because of the small but important risk for myocardial infarction, DDAVP should be used with caution in any surgical patient with a history of or risk factors for coronary artery disease.

Topical Hemostatic Agents

Topical hemostatic agents can be grouped into several categories: physical agents such as bone wax or alkylene oxide copolymers (Ostene), absorbable agents such as gelatin foams, oxidized cellulose, or microfibrillar collagen, biologic agents such as topical thrombin, fibrin sealants, or platelet gels, synthetic agents such as polyethylene glycol hydrogels, cyanoacrylates, glutaraldehyde or cross-linked albumin, and hemostatic dressings. A thorough discussion of the currently available products, including mechanisms of action, specific advantages and disadvantages, and recommendations for their use is provided in a comprehensive review. A brief overview of the different types of topical hemostatic agents follows.