Acute normovolaemic haemodilution during anaesthesia in a polycythaemic French Bulldog presented for transvalvular pulmonic stent angioplasty

Abstract

A 2-year-old, female entire French Bulldog was presented for exercise intolerance, tachypnoea and cyanosis. Severe pulmonic stenosis and hypoplasia with a right-to-left shunting patent foramen ovale was identified on echocardiography. Polycythaemia was present on initial haematology. Minimally invasive transvalvular pulmonic stent angioplasty (TPSA) was scheduled to improve blood flow to the pulmonary circulation and reduce shunt fraction. Anaesthesia was induced with fentanyl, midazolam and propofol administered intravenously to effect. Anaesthesia was maintained with propofol, fentanyl and lidocaine infusions. Following induction, the dog had a haemoglobin oxygen saturation (SpO₂) of 76% and was hypotensive, requiring a noradrenaline infusion to correct it. After blood pressure stabilization and prior to TPSA, acute normovolaemic haemodilution was performed to reduce haematocrit and blood viscosity to improve oxygen delivery. Following acute normovolaemic haemodilution, SpO₂ and blood pressure improved, suggesting this may be a valid technique for managing these cases. TPSA was performed, with three stents placed in the right ventricular outflow tract owing to severe outflow tract obstruction. Immediate postoperative complications included prolonged recovery, regurgitation and hypoxaemia. The dog presented 3 days later with haemorrhagic regurgitation and melaena and again 18 days post-procedure with acute dyspnoea, suspected to be due to pulmonary thromboembolism, and was euthanized due to poor prognosis. Management of dogs with right-to-left anatomical shunts is extremely complex and the high risk of thromboembolism secondary to polycythaemia should not be underestimated. Perioperative acute normovolaemic haemodilution may be used to improve haemodynamics and oxygen delivery.