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Haematological emergencies

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Abstract

Anaemia, bleeding disorders and thromboembolism are all life-threatening conditions, rapid diagnosis and timely intervention are essential to mitigate the risk of death. This chapter considers the emergency approach, history and clinical examination, laboratory assessment, diagnostics and treatment of anaemia, primary and secondary bleeding disorders, hypercoagulation and thrombosis

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Figures

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13.2 Blood typing must be performed before any feline red cell transfusion. Fatal haemolytic reactions can occur, particularly in blood group B cats administered type A blood. Feline blood typing can be achieved at the point of care using card assays, gel-based systems or immunochromatographic cartridges such as the one shown (DME VET A+B, Alvedia; see Chapter 14).
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13.3 All patients receiving a transfusion should be closely monitored and the data recorded using dedicated forms, to improve identification of a transfusion reaction.
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13.4 The plasma component of the blood in microhaematocrit tubes should be scrutinized for haemoglobinaemia or hyperbilirubinaemia. Serial monitoring of these tubes provides a quick visual readout of a patient’s progress, here used to monitor a dog with immune-mediated haemolytic anaemia receiving immunosuppressive drugs.
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13.6 Diff-Quik stained blood smear of a dog with immune-mediated haemolytic anaemia, demonstrating marked polychromasia, anisocytosis, spherocytosis and the presence of nucleated red blood cells (normoblasts).
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13.7 Non-regenerative anaemia due to myelophthisis in a patient with lymphoblastic leukaemia.
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13.8 Punctate and aggregate reticulocytes in a cat with regenerative anaemia. (Courtesy of T Stokol, Cornell University)
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13.9 (a) Macroagglutination and (b) microagglutination (original magnification X400) from a dog with immune-mediated haemolytic anaemia.
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13.12 Anaemia may be secondary to infectious diseases in both dogs and cats. Here punctate forms of (a) can be seen associated with the erythrocyte membrane. (b) The characteristic basophilic piriform shapes of can be clearly seen in the erythrocytes of this dog with a history of travel to Spain.
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13.13 (a) Profound haemoglobinuria due to zinc intoxication secondary to ingestion of (b) a large number of zinc-containing coins. UK £1 and £2 coins, higher denomination Euros and US pennies are common sources of zinc. Immune-mediated haemolytic anaemia is the major differential diagnosis for the haemolysis of zinc intoxication, and differentiating the two can be challenging because spherocytosis can also occur in zinc intoxication.
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13.14 In contrast to immune-mediated haemolytic anaemia patients, dogs with zinc intoxication typically have evidence of metallic foreign bodies. Abdominal radiography confirms the presence of the foreign objects, although zinc-containing skin creams may be more difficult to identify radiographically. The dog in this radiograph developed marked haemolysis necessitating transfusion of packed red blood cells. Endoscopic removal of the objects (zinc washers) led to a rapid resolution of clinical signs.
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13.15 Heinz bodies in (a) a cat and (b) a dog, following onion ingestion. Both were stained using modified Wright’s stain. (Courtesy of T Stokol, Cornell University)
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13.16 The presence of schistocytes (sheared erythrocytes) on blood smear examination should alert the clinician to the possibility of microangiopathic disorders such as disseminated intravascular coagulation or haemangiosarcoma. Schistocytes may also be seen in patients with caval syndrome associated with dirofilariasis. (Courtesy of T Stokol, Cornell University)
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13.18 Physical examination abnormalities consistent with a primary haemostatic disorder. (a) Petechiation. (b) Ecchymoses. (c) Inguinal bruising. (d) Episcleral (subconjunctival) haemorrhage. (e) Mild hyphaema noted as iris haemorrhage. (f) Marked hyphaema with blood in the anterior chamber.
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13.21 Macroplatelets can indicate platelet regeneration or may be breed associated, particularly in Cavalier King Charles Spaniels. (Courtesy of T Stokol, Cornell University)
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13.22 Evaluation of the buccal mucosal bleeding time is indicated to investigate primary haemostatic abnormalities when the platelet count is normal.
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13.23 Evaluation of -dimers at the point of care can aid the timely diagnosis of disseminated intravascular coagulation or thromboembolic disease. Several point-of-care assays have been evaluated for use in dogs, including the NycoCard -dimer assay illustrated here. (Courtesy of D Chan, Royal Veterinary College)
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13.24 Potential thrombopathias can be investigated at the point of care using specific platelet function analysers such as the PFA-100. This particular analyser enables testing of platelet aggregate formation under high-shear conditions and can evaluate several distinct pathways of platelet activation.
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13.25 Whole blood viscoelastic tests of coagulation such as (a) thromboelastography are increasingly used in veterinary emergency and critical care to screen for hypo- and hypercoagulability. These assays may also enable identification of fibrinolytic disorders. Characteristic thromboelastography traces of patients with (b) hypocoagulability, (c) hypercoagulability and (d) hyperfibrinolysis are illustrated here.
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13.27 A Dobermann with von Willebrand’s disease receiving a plasma transfusion in the emergency room. Transfusion therapy is frequently required in the treatment of bleeding disorders.

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