Page 70 - Williams Hematology ( PDFDrive )

46 Part I: Clinical Evaluation of the Patient Chapter 4: Consultative Hematology 47

variant of preeclampsia is the HELLP syndrome (Chaps. 8 and 51), an Before deciding that a prolonged PT or PTT is because of a factor
emergency where low platelets are accompanied by microangiopathic deficiency, consider the possibility of an inhibitor by ordering a mixing
hemolysis and hepatic dysfunction. The blood film and liver function study. If an inhibitor is ruled out, then one can determine whether spe-
tests are essential in making this diagnosis. cific factor assays are warranted. A prolonged PTT might also be the
Disorders of hemostasis/coagulation include placental abruption result of a lupus anticoagulant, which generally poses a risk for throm-
and retained products of conception. These two conditions are unique bosis rather than hemorrhage.
to pregnancy and release large amounts of necrotic tissue into the cir- If there is recurrent mucosal bleeding and a family history of
culation, leading to DIC (Chap. 129). The consultant is often called bleeding, we generally obtain screening for VWD. A platelet function
because of severe bleeding from many sites, including the vagina, analysis (PFA) is a highly sensitive test for VWD. Additional tests, such
vascular access sites, and surgical incisions. Laboratory findings often as a von Willebrand antigen, ristocetin cofactor activity, and factor VIII
demonstrate profound anemia and thrombocytopenia, and the blood levels can be used to confirm the diagnosis. More expensive studies,
film shows microangiopathy. The coagulation panel demonstrates a such as multimer analysis and ristocetin-induced platelet aggregation
prolonged prothrombin time (PT) and partial thromboplastin time (RIPA) are generally not needed if screening studies are negative. A
(PTT), low fibrinogen, and significantly elevated D-dimer. If assayed, variety of disorders are associated with acquired VWD, including car-
virtually all coagulation factors will be low. The key to management is diac valvular disorders, extreme thrombocytosis, paraproteinemias, and
prompt recognition, establishment of adequate IV access, and massive autoimmune disorders (Chap. 126).
replacement of RBCs, platelets, and coagulation factors, along with Mucosal or posttraumatic bleeding might also suggest a platelet
removal of the uterine contents. functional defect. Screening with a PFA is often useful before launching
Two disorders have a specific predilection for the immediate post- into more detailed studies, such as formal platelet aggregometry.
partum period: appearance of a factor VIII inhibitor and postpartum A low fibrinogen and markedly elevated D-dimer points to DIC,
TTP. Patients with a factor VIII inhibitor will show a long PTT and mix- which can be seen in a variety of systemic illnesses and is associated
ing studies will identify and quantify the inhibitor. Patients with post- with both bleeding and thrombosis.
partum TTP will have a clinical presentation like other TTP patients: Of course, not all bleeding is related to disorders of coagulation
microangiopathic hemolysis, thrombocytopenia, and potentially CNS factors and platelets. One should not forget vasculitis or other vascu-
and renal involvement. lar defects, such as hereditary hemorrhagic telangiectasia (HHT), when
evaluating a patient with recurrent mucosal bleeding and epistaxis.
BLEEDING Vitamin C deficiency (scurvy) can rarely be encountered in alcoholics
or severely malnourished individuals and results in bruising and gin-
Clinical bleeding is a common request for hematologic consultation. gival bleeding because of defective collagen synthesis.
The setting and context provide important clues about the diagnosis. Pathologic fibrinolysis may also result in bleeding and is not easily
Requests arising from the ICU or emergency room (ER) usually relate assessed by standard coagulation panels (Chap. 135).
to a specific event like trauma or surgery. These requests may involve We have used thromboelastography to evaluate global hemosta-
hemodynamic compromise and often mandate a rapid response. Con- sis on an individualized basis, although this study lacks broad clinical
versely, complaints about “easy bruising” can be equally ominous, but utility.
often don’t rise to the same level of acuity. Finally, preoperative consultations for bleeding can be frustrating
The conventional wisdom is that mucosal and skin bleeding is because there are no generally accepted guidelines. The most important
likely to be caused by platelet abnormalities (qualitative or quantita- tool is the history including family and personal history of bleeding. The
tive), vascular disorders, or VWD, whereas deep tissue or joint bleeding type, site, and timing of prior episodes of bleeding, whether postopera-
is caused by coagulation factor deficiencies. This is generally accurate, tive, traumatic, or spontaneous, provide the requisite information upon
although there is substantial overlap caused by factors like age and which to base further testing as discussed above.
comorbid medications (including aspirin, nonsteroidal antiinflamma-
tory drugs [NSAIDs], and anticoagulants).
As expected, the history is critical. One must inquire about bleed- THROMBOSIS
ing length, duration, and context. A long duration and early onset sug-
gest a hereditary disorder. Bleedings that occurs after dental extractions VENOUS THROMBOSIS
or surgery are clues for mild hemophilia or VWD. If the bleeding always Consultations regarding deep venous thrombosis (DVT) may be daunt-
occurs at one site, there may well be a local issue, whereas bleeding at ing. The decision to commit a young patient to indefinite anticoag-
multiple sites points to a systemic disorder. Drug history is critical, not ulation (AC), or to cease AC in an older patient at increased risk for
only for anticoagulant drugs, but also for the many agents that cause recurrence often gives the physician pause.
drug-induced platelet functional abnormalities (Chap. 121). A history Here we discuss some of the highlights of our approach to venous
of alcohol abuse, hepatic disease, or renal disease is relevant. thromboembolism. The individual components are discussed at length
The exam should be used to identify petechiae, oral blood blisters, in other chapters, including principles of AC (Chap. 25), DVT (Chap.
ecchymoses, hematomas, giant hemangiomas, hemarthroses, and liver/ 133), hereditary thrombophilia (Chap. 130), and the antiphospholipid
spleen size. antibody syndrome (APS; Chap. 131).
Laboratory analysis should include a blood film, CBC, and chem- Patients often have significant anxiety after a thrombotic event.
istry panel. A basic coagulation panel containing a PT, PTT, fibrinogen, Although considerable progress has been made in the safety and con-
D-dimer, thrombin time (TT), and reptilase time (RT) is also important venience of AC, the process still poses serious risk and may impair
(Chaps. 114 and 116). The PT and PTT screen both the intrinsic and the patient’s quality of life. It is important to communicate that AC
extrinsic pathways. The fibrinogen and D-dimer provide useful infor- management is inherently complex, therapeutic approaches must be
mation about DIC and fibrinolysis, while a discrepancy between the RT individualized, and, ultimately, no approach is without risk, including
and TT can determine whether there is in vivo presence of heparin. life-threatening bleeding and/or thrombosis.

Kaushansky_chapter 04_p0041-0050.indd 46 17/09/15 5:42 pm