Reply To: Acute dyspnoea and small stature in a domestic shorthair cat

Thanks so much for picking this discussion back up! 🙂

Initially the patient was placed in an oxygen chamber. Butorphanol 0.3mg/kg was administered, intramuscularly. After twenty minutes, the patient’s respiratory rate was still 50 breaths per minute and no change in respiratory effort was noted. The patient was removed from the oxygen chamber and flow-by oxygen therapy was administered. It was not possible to obtain an arterial blood sample. An intravenous catheter was placed into the right cephalic vein. A venous blood sample was obtained for a minimum database (PCV, total solids, glucose and blood urea nitrogen (BUN)), acid-base analysis, electrolytes and haematology. Manual PCV and total solids were 74g/l and 70g/l respectively. Both glucose and BUN were within the normal reference range. The patient was hyperkalaemic; 4.8mmol/L (2.9 – 4.2). Haematocrit was 72% (24-40) and cHgb was 24.4 g/dL (8.0-13.0). All other haematological and electrolyte results were within the normal reference range. Coagulation testing showed that partial prothrombin (PT) time was within the normal reference range, however activated partial thromboplastin time (aPPT) was mildly prolonged at 167.2s (94-125) (Table 2). A thoracic ‘point of care’ ultrasound examination was performed and was negative for free fluid. Subjectively the left atrium was dilated with an abnormal left atrial to aortic (LA:Ao) ratio, however further assessment of the heart was not possible due to the cat’s temperament. No free fluid was present on abdominal point of care ultrasound. SpO2 was 97% from pinna.

It was initially suspected that the patient’s haemoconcentration was due to severe dehydration. As such, a fluid therapy plan was implemented. A 15ml/kg intravenous fluid bolus of Hartmann’s solution (Vetivex 11; Dechra) was administered over 15 minutes, after which intravenous fluid therapy (IVFT) was continued at a rate of 4ml/kg/hr for eight hours . Seven hours post presentation the patients PCV was 67%, and IVFT was continued at a reduced rate of 2ml/kg/hr thereafter. After twenty-four hours of fluid therapy the patient’s PCV was 65%. The patient was quiet, alert and responsive; however, the breathing had become more laboured despite continued oxygen therapy, and her respiratory rate was consistently between 60-70 breaths per minute .

The PCV and haematocrit are elevated, indicating that the patient is polycythemic; PCV>55%. It is important to distinguish between a relative polycythemia and an absolute polycythemia. Relative polycythemia is the loss of plasma water without the loss of red blood cells. It is caused by fluid imbalances causing reduced plasma fluid volume, such as dehydration, reduce fluid intake, redistribution of vascular blood, cutaneous losses or splenic contraction (in the dog). Absolute polycythemia occurs when red blood cell number increases and is classed as either primary or secondary. Despite fluid therapy, although slightly improved, the patient’s PCV was still significantly increased and as such this case is termed an absolute polycythemia.

What would be the differentials for an absoute polycythemia in this patient? Or is that an unfair question for a saturday night?!?!?

Scott 🙂