Page 2587 - Hematology_ Basic Principles and Practice ( PDFDrive )

C H A P T E R 159

HEMATOLOGIC PROBLEMS IN THE SURGICAL PATIENT:

BLEEDING AND THROMBOSIS

Iqbal H. Jaffer, Mark T. Reding, Nigel S. Key, and Jeffrey I. Weitz

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Surgical patients often present unique challenges to the consulting bleeding. Another study found that perioperative blood loss in adult
hematologist. They may develop hemostatic disorders ranging from cardiothoracic surgery patients could be predicted with a model,
unexpected bleeding to pathologic thrombosis, both of which can be which included the bleeding time, prothrombin time (PT), and
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potentially life threatening. Consultation may be sought to assess platelet count. Given the variety of potential hemostatic defects
preoperative bleeding risk and/or to recommend strategies to prevent however, no simple screening system will identify all patients at
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postoperative thrombosis. The hematologist may be called upon to increased risk for bleeding. Those against routine laboratory testing
assist in the management of patients with a previous history of point to retrospective studies indicating that they rarely detect unex-
bleeding or thrombosis and in those with unexplained bleeding pected bleeding disorders 10,11 and emphasize the problems associated
or thrombosis in the perioperative period. This chapter will review: with evaluation of false-positive results. A literature review found
(1) the preoperative evaluation of bleeding risk; (2) strategies to insufficient evidence to conclude that an abnormal PT/international
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aid intraoperative hemostasis; (3) the management of patients with normalized ratio (INR) predicts bleeding during invasive procedures.
hemostatic abnormalities or those taking long-term oral anticoagula- A retrospective review of the value of preoperative determination of
tion; and (4) the perioperative prevention of venous thromboembo- the platelet count, PT, and activated partial thromboplastin time
lism (VTE). (aPTT) in 828 patients undergoing major noncardiac surgery found
that only 2% had abnormal results, and most were expected on the
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basis of history and physical examination. Furthermore, abnormal
PREOPERATIVE EVALUATION OF HEMOSTATIC RISK laboratory test results and intraoperative blood loss or postoperative
bleeding complications were not related. This is not surprising given
History the lack of studies using an evidence-based approach to determine
the degree of abnormality in the PT/INR or aPTT at which invasive
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Preoperative evaluation of hemostatic risk begins with a carefully procedures may be unsafe. A number of prospective studies have
taken history. Particular attention should be directed at specific bleed- also concluded that routine laboratory screening tests in asymptom-
ing symptoms and any history of bleeding associated with surgical atic patients are not predictive of perioperative or postoperative
procedures, including circumcision, tonsillectomy, and dental extrac- bleeding. 15-19 Thus in the absence of historical risk factors or physical
tions. For women, it is important to inquire about a history of menor- examination findings suggestive of an underlying bleeding tendency,
rhagia or excessive bleeding associated with childbirth. A detailed the likelihood of an unsuspected, clinically significant congenital or
family history and record of medication use, including nonprescrip- acquired coagulopathy is low enough that routine laboratory screen-
tion medications, should be obtained. In adults, an interview to assess ing is not warranted, particularly for those undergoing low-risk
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for the presence or absence of bleeding symptoms has a high discrimi- procedures. The British Committee for Standards in Haematology
nating power when used in a screening situation, where no bleeding recently issued guidelines reiterating this position: indiscriminate
disorder is suspected, but may be less discriminatory for those referred coagulation testing before surgical or invasive procedures is a poor
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for specialty evaluation. In the pediatric population, the medical predictor of bleeding risk and is not recommended in the absence of
history may be less reliable as a screening method because of fewer a positive personal or family bleeding history. 21
previous hemostatic challenges. 2 There are a variety of reasons why routine coagulation tests such
Obtaining an adequate bleeding history may be complicated by as the PT/INR and aPTT may be poorly predictive of underlying
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the fact that even in the absence of hemostatic defects, many people coagulopathy and bleeding risk. First, these tests were designed to
consider their bleeding to be excessive. Surveys of healthy individuals measure time to clot formation in artificial in vitro assays and do not
frequently report excessive nosebleeds (5%–39%), gingival bleeding reliably depict the global hemostatic situation in vivo (see Liver
(7%–51%), easy bruising (12%–24%), menorrhagia (23%–44%), Disease section). More importantly, the PT/INR and aPTT may be
postpartum bleeding (6%–23%), and bleeding following dental insensitive to mild but clinically relevant bleeding disorders such as
extraction (up to 13%) and tonsillectomy (up to 11%). 1,3,4 Thus a von Willebrand disease or mild hemophilia. Conversely, they may
thorough search for objective confirmation of reported symptoms is detect conditions such as factor XII deficiency or a lupus anticoagu-
essential. Also, a constellation of bleeding symptoms, rather than any lant that do not increase the risk for bleeding.
single symptom, is most helpful in suggesting the presence and etiol- The platelet function analyzer (PFA-100) has been developed for
ogy of an underlying bleeding disorder. rapid, quantitative in vitro global testing of platelet function. 22,23 The
clinical sensitivity (94%–95%) and specificity (88%–89%) of this
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instrument are virtually identical to platelet aggregometery.
Coagulation Testing Although some have suggested that the PFA-100 could be used for
screening for primary hemostatic defects, such testing has limita-
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The need for routine coagulation testing before surgical or invasive tions. The PFA-100 has high sensitivity for detection of moderate-
procedures remains controversial. Those in favor of testing point to to-severe von Willebrand disease and severe platelet defects, such as
the asymptomatic nature of some hemostatic abnormalities that may Glanzmann thrombasthenia and Bernard-Soulier syndrome, but it
cause surgical bleeding and the occasional failure to obtain a detailed has poor sensitivity for detection of milder platelet disorders such as
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history. A prospective study of preoperative screening in children storage pool disease, Hermansky-Pudlak syndrome, and primary
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before tonsillectomy found history and laboratory screening to have secretion defects. Although the PFA-100 is most useful when a
high specificity but a low positive-predictive value for perioperative hemostatic defect is clinically likely, in such cases additional testing
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