A 12-year-old, 20 kg, castrated male Cocker Spaniel presented for evaluation of a 48-hour history of anemia, icterus, and anorexia. Physical examination identified dull mentation, icterus, tachycardia (170 beats/min), tachypnea (60 breaths/min), dyspnea, profound weakness, and a grade IV/VI left apical systolic heart murmur. CBC including blood smear examination revealed an anemia (hematocrit 0.13 L/L, reference range, 0.39-0.56 L/L), neutrophilia (28.63Â10 9 /L, reference range, 2.9-10.6Â10 9 /L), spherocytosis, and auto-agglutination. Pertinent biochemical profile abnormalities included hypokalemia (2.94 mEq/L, reference range, 3.8-5.4 mEq/L), hyperchloremia (122 mEq/L, reference range, 104-119 mEq/L), hypoalbuminemia (2.4 g/dL, reference range, 2.9-4.3 g/dL), hyperbilirubinemia (8.13 mg/dL, reference range, 0-0.23 mg/dL), and increased alanine transferase (445 U/L, reference range, 10-107 U/L), and alkaline phosphatase (532 U/L, reference range, 22-143 U/L) activity. Results of coagulation testing were unremarkable. Urinalysis revealed a urine specific gravity of 1.042, bilirubinuria, hemoglobinuria, pH 8.5, struvite crystalluria, and a catheterized urine sample for culture yielded no bacterial growth. Left atrial enlargement was noted on thoracic radiographs and was consistent with mitral valve endocardiosis. Abdominal ultrasound examination was unremarkable. These changes were consistent with a diagnosis of primary immune-mediated hemolytic anemia (IMHA).Treatment for IMHA was instituted with dexamethasone sodium phosphate a (0.25 mg/kg IV q24h), azathioprine b (2 mg/kg PO q24h), a packed red blood cell transfusion (13 mL/kg), a heparin c infusion (500 U/ kg/d IV), and famotidine d (0.5 mg/kg IV q12h). IV administration of a maintenance fluid solution e was commenced (75 mL/h IV), and potassium chloride f was administered as a constant rate infusion over 4 hours (0.5 mEq/kg/h, IV) to treat hypokalemia.Results of venous blood gas analysis on hospital admission revealed a metabolic acidosis and a normal anion gap ( g in sterile water (supplemented with 20 mEq/L of potassium chloride) was administered IV at a maintenance fluid rate to correct the plasma bicarbonate concentration to 18 mEq/L over a 12-hour period; however, bicarbonate increased to only 15.1 mEq/L after 12 hours of infusion. Supplementation was continued (4 mEq/kg/d sodium bicarbonate IV) throughout hospitalization and plasma bicarbonate concentration increased and remained between 18.1 and 19.7 mEq/L and blood pH was maintained at 7.37.Increased respiratory effort persisted that was not responsive to oxygen supplementation. Arterial blood gas analysis (day 3) on nasal oxygen supplementation was suggestive of pulmonary thromboembolism (P a CO 2 20 mmHg, reference range, 23-40 mmHg; P a O 2 68.3 mmHg, reference range, 80-112 mmHg). Despite improvement in the PCV, the dog continued to deteriorate and euthanasia was elected and postmortem examination declined.A 6.5-year-old, 40 kg, castrated male Coonhound presented for evaluation after a 72-hour h...