Open Heart Surgery with Deep Hypothermia and Cardiopulmonary Bypass in Small and Toy Dogs

Abstract

To evaluate open heart surgery with deep surface-induced hypothermia (sHT) and low-flow cardiopulmonary bypass (CPB) in small and toy-breed dogs. Case series. Small breed dogs (n=8) weighing <5.5 kg with naturally occurring cardiac disease. Deep sHT under isoflurane anesthesia and low-flow rate CPB with a small-volume prime circuit were used. Ventricular septal defect was closed directly in 2 dogs and severe mitral regurgitation was corrected with mitral valvuloplasty (MVP) in 5 dogs and mitral valve replacement in 1 dog. All dogs survived surgery; 1 dog died 6 days and 1 died 2 months after MVP. The other 6 dogs lived (mean follow-up, 32.8 months; range, 12-65 months). Mean body weight at surgery was 3.6 kg (range, 2-5.3 kg). Mean lowest esophageal temperature was 21.4 degrees C (range, 19.8-23.8 degrees C). Mean lowest pump flow volume was 29.2 mL/kg/min (range, 9.4-57.7 mL/kg/min) during aortic cross-clamping (mean, 53.5 minutes; range, 25-79 minutes). Mean hematocrit before CPB was 38.6% (range, 33-47%) and 20.3% (range, 13-24%) during CPB with a small circuit priming volume of 225-260 mL. Deep sHT with low-flow rate CPB may be used for open heart surgery in small dogs weighing <5.5 kg. Open heart surgery for selected congenital defects and acquired defects in small and toy-breed dogs may be successfully performed using deep sHT and CPB.