Page 1417 - Small Animal Internal Medicine, 6th Edition

CHAPTER 87 Disorders of Hemostasis 1389

is a delayed, continuous, long-lasting bleed, leading to hema- CLINICOPATHOLOGIC EVALUATION OF
toma formation or bleeding into a body cavity. This is analo- THE BLEEDING PATIENT
VetBooks.ir gous to turning on a faucet connected to a regular garden Clinicopathologic evaluation of the hemostatic system is
hose with a single large opening; in this situation, water
(blood) continues to flow and collect in large amounts next
spontaneous or prolonged bleeding, and before surgery in
to the opening in the hose (vessel; see Fig. 87.3, B). indicated primarily in two subsets of patients: in those with
Spontaneous bleeding infrequently occurs in cats and patients with disorders commonly associated with bleeding
dogs with excessive fibrinolysis. I have evaluated a limited tendencies (e.g., splenic hemangiosarcoma [HSA] and DIC
number of dogs with protein-losing nephropathy and in dogs; liver disease and clotting factor deficiency in dogs
nephrotic syndrome in which spontaneous bleeding (i.e., and cats) or a suspected congenital coagulopathy (e.g., before
petechiae and ecchymoses) appeared to result from enhanced ovariohysterectomy in a Doberman Pinscher suspected of
fibrinolysis. However, fibrinolysis is relatively difficult to having subclinical vWD).
evaluate using laboratory methods other than thromboelas- When evaluating a cat or dog with a spontaneous bleed-
tography (TEG), so additional data are being currently gen- ing disorder, the clinician should keep in mind that the pre-
erated on this area. liminary clinical diagnosis can usually be confirmed by
Dogs (and cats) with primary hemostatic defects (i.e., performing some simple point-of-care (real-time) tests. If
platelet disorders) therefore have typical manifestations of these tests do not yield a definitive answer, or if a more spe-
superficial bleeding, consisting of petechiae, ecchymoses, cific diagnosis is needed (e.g., the identification of specific
bleeding from mucosal surfaces (e.g., melena, hematochezia, clotting factor deficiencies), a plasma sample can be submit-
epistaxis, hematuria), and prolonged bleeding immediately ted to a referral veterinary diagnostic laboratory or special-
after venipuncture. In clinical practice, most primary hemo- ized coagulation laboratory (e.g., New York State Diagnostic
static disorders are caused by decreased numbers of circulat- Laboratory, Cornell University, Ithaca, NY). As discussed
ing platelets (thrombocytopenia). Recently, a bleeding score later, TEG is now widely used to evaluate patients with
for thrombocytopenic dogs was proposed for dogs (Makiel- coagulopathies.
ski et al., 2018). Primary hemostatic defects occasionally Some simple point-of-care tests include the evaluation of
result from primary or secondary platelet dysfunction (e.g., a blood smear or the graphics from the hematology analyzer;
uremia, vWD, monoclonal gammopathies, vector-borne dis- determination of the ACT, one-stage prothrombin time
eases). Primary hemostatic defects caused by vascular disor- (OSPT), and APTT; quantification of FDP or D-dimer con-
ders are extremely rare in cats and dogs and will not be centrations; and buccal mucosa bleeding time (BMBT; Table
discussed. 87.1). Examination of a good-quality, well-stained blood
Clinical signs in dogs and cats with secondary hemo- smear (e.g., Diff-Quik) provides important clues regarding
static defects (i.e., clotting factor deficiencies) consist of platelet numbers and morphology, as does evaluation of
deep bleeding, including bleeding into body cavities and graphics generated by flow cytometry hematology analyzers.
joints, and deep hematomas, most of which are discov- The first part of this examination should involve scan-
ered as a lump or mass. Certain congenital coagulopathies, ning the smear at low power to identify platelet clumps;
including factor XII, prekallikrein, and HMWK deficien-
cies, result in a marked prolongation of the activated coag- TABLE 87.1
ulation time (ACT) or activated partial thromboplastin
time (aPTT) without spontaneous or prolonged bleeding Simple Point-of-Care Tests for Rapid Classification of
(see later). Hemostatic Disorders
Most secondary bleeding disorders seen in clinical prac-
tice are caused by rodenticide poisoning or liver disease; MOST LIKELY
selective congenital clotting factor deficiencies occasionally TEST RESULTS DISORDER(S)*
can lead to spontaneous secondary bleeding disorders. A
combination of primary and secondary bleeding disorders Platelet estimation Low Thrombocytopenia
in blood smear
(mixed disorders) is seen almost exclusively in dogs and cats
with DIC. ACT Prolonged Intrinsic, common system
We recently described a syndrome of delayed postopera- defect
tive bleeding in former racing Greyhounds that occurs in FDP–D-dimer Positive Enhanced fibrinolysis,
approximately 25% to 30% of dogs who undergo surgery. It thrombosis,
consists of superficial bleeding around the surgical site start- thromboembolism, DIC
ing 36 to 48 hours after the surgery, which becomes systemic BMBT Prolonged Thrombocytopenia,
and is often life-threatening (Lara García et al., 2008; Marin thrombocytopathia
et al., 2012a and b). We have also observed a similar syn- ACT, Activated clotting time; BMBT, buccal mucosa bleeding time;
drome in other sighthound breeds, including Deerhounds DIC, disseminated intravascular coagulation; FDP, fibrin
and Italian Greyhounds. For additional discussion, see degradation product.
Chapter 83. *If prolonged (or positive).