Page 2089 - Cote clinical veterinary advisor dogs and cats 4th

1044 von Willebrand Disease

Initial Database results of confirmatory tests (see Advanced or dosage is 1 mcg/kg SQ given 30 minutes
• Thorough physical exam to define single Confirmatory Testing above): preoperatively.
VetBooks.ir • Baseline hematocrit and plasma protein: levels of VWF to control active hemorrhage transfusion should be available if hemor-
○ The response to DDAVP varies, and
versus multiple sites of hemorrhage
• Transfusion (p. 1169) can supply hemostatic
rhage develops despite DDAVP therapy.
refractory to local wound care. Patients with
normal, or decreased if bleeding is severe
and chronic
may require additional transfusions within
• Platelet count or platelet estimate from blood severe VWD (typically types 2 and 3 VWD) • Development of endocrinopathy (e.g.,
hypothyroidism, hypoadrenocorticism) or
smear: usually normal the first 24 hours to sustain hemostasis after thrombocytopenia may exacerbate the
• Point-of-care coagulation screening tests: an initial response. bleeding tendency of VWF-deficient patients.
usually normal • Transfusion of plasma components reduces Identification and correction of these disor-
○ Activated clotting time (ACT) risk of volume overload or red cell sensitiza- ders can reduce risk of clinical signs.
○ Activated partial thromboplastin time tion while maximizing VWF replacement.
(aPTT) • Fresh-frozen plasma 10-15 mL/kg IV Behavior/Exercise
○ Prothrombin time (PT) ○ Transfuse at the high end of dosage range von Willebrand disease, unlike hemophilia
• Bleeding time (buccal mucosal bleeding for the initial transfusion. and other hereditary coagulopathies, does not
time): increased (p. 1076) ○ Severely deficient patients may require cause hemarthrosis. Exercise restrictions are
repeated transfusions at q 8-12h intervals. unwarranted, but sharp sticks or chew toys
Advanced or Confirmatory Testing • Cryoprecipitate (unit dosage varies by should be avoided to prevent oral mucosal
Diagnosis is based on specific measurement of supplier) injuries.
plasma VWF concentration: ○ Prepared from fresh-frozen plasma and
• VWF concentration (VWF:Ag) contains a 5- to 10-fold concentration Drug Interactions
○ VWF:Ag < 50% is evidence of VWF of VWF in approximately one-tenth the Avoid drugs with anticoagulant or antiplatelet
deficiency, but clinical bleeding tendency volume of the starting plasma. effects in animals with VWD:
is usually seen in animals having more ○ Cryoprecipitate’s low volume eliminates • Nonsteroidal antiinflammatory drugs
severe deficiency (<25%). the risk of volume overload if repeated (NSAIDs)
○ Types 1 and 2 VWD in dogs are char- transfusion is needed for high-dose VWF • Sulfonamide antibiotics
acterized by the presence of low protein replacement. • Heparin, warfarin (Coumadin)
concentration, whereas type 3 VWD is • Fresh whole blood (12-20 mL/kg) can • Plasma expanders
characterized by a complete absence of be used as a source of VWF replacement • Estrogens
VWF (VWF:Ag < 0.1%). if plasma components are unavailable or • Cytotoxic drugs
• Differentiation of types 1 and 2 VWD is replacement of red blood cells (RBCs) and
based on the finding of dysfunctional and VWF is desired to treat ongoing blood-loss Possible Complications
structurally abnormal protein in the type 2 anemia: RBC sensitization causing transfusion reactions:
form. Abnormal protein is identified based ○ Risk of volume overload generally limits • Transfuse plasma components when possible.
on the following tests: whole blood transfusion to q 24h intervals • Dogs with severe VWD should be blood
○ VWF:CB = VWF collagen binding activity (p. 989). typed because repeated transfusion may be
(functional assay) • Packed RBC transfusion 6-12 mL/kg is required. Choose type-matched donors for
○ VWF multimer analyses = Western blot indicated to treat severe blood-loss anemia. RBC or whole blood transfusions.
to visualize VWF subunit structure • Use local wound care (suture, pressure wrap, • Canine transfusion: after a first RBC
• Hereditary type 2 VWD has been identified tissue glue) to help control bleeding from transfusion, perform a cross-match before
in only two breeds: German wirehaired and superficial sites. subsequent transfusions.
short-haired pointers.
• An acquired type 2 VWD occurs in human Chronic Treatment Recommended Monitoring
beings with aortic stenosis. A study of mitral • Intermittent transfusion may be needed to Demonstration of adequate VWF replacement:
valve disease in Cavalier King Charles control hemorrhagic events in patients with • Cessation of active bleeding
spaniels revealed abnormal VWF multimer severe (types 2 and 3) VWD. • Stabilization of hematocrit/plasma protein
distribution, compatible with type 2 VWD. • Preoperative transfusion to patients with
type 2 or 3 VWD or severe expression of PROGNOSIS & OUTCOME
TREATMENT type 1 VWD to replace VWF before surgical
procedures • Most dogs clinically affected with VWD have
Treatment Overview ○ Fresh-frozen plasma and cryoprecipitate a good quality of life and require transfusions
• Control active bleeding with transfusion are the best products for preoperative intermittently or rarely:
therapy and local wound care. prophylaxis: same dose as described ○ Animals with severe VWD (types 2 and
• Avoid unnecessary surgery, trauma, and any previously 3 VWD) are most likely to develop
drug therapy that inhibits platelet function ○ Transfusion is administered just before the spontaneous bleeding or require repeated
or coagulation factor activity. surgical procedure. Peak VWF is obtained transfusion. All dogs affected with types 2
• Correct any underlying medical conditions immediately after transfusion, and values and 3 VWD should receive a preoperative
that may impair hemostasis. fall to baseline by 24 hours. transfusion before surgical procedures.
○ Close monitoring is required during ○ Many dogs with type 1 VWD have
Acute General Treatment the first 24 hours after the operation. mild disease expression. Clinical signs
A patient that had a normal preoperative Repeat transfusion (q 8-12h) may be of abnormal bleeding are most likely to
platelet count but bleeds persistently during a required during this period for severe develop in dogs with VWF:Ag < 25%.
surgical procedure, shows no physical evidence VWD. • Acute bleeding crises may require intensive
of severe systemic illness (vasculitis), and is not • Desmopressin acetate (deamino-8-D-arginine transfusion support to rapidly provide
known to have been exposed to anticoagulant vasopressin [DDAVP]) is a synthetic vaso- hemostatic levels of VWF protein. Initial
(e.g., rodenticide) or antiplatelet (e.g., aspirin) pressin analog that can be used preoperatively high-dose component therapy (fresh-frozen
substances should be suspected of having VWD to enhance surgical hemostasis in patients plasma or cryoprecipitate) is recommended
and may be treated as follows pending the with mild to moderate VWD (type 1 VWD); to control severe bleeding.

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