Hypothermic anesthesia using ether was applied for 2 dogs with patent ductus arteriosus. The ductus arteriosus was ligated when the esophageal temperature failed to 26°C or 26.8°C, at which time the arterial blood pressure decreased to 55/25 mmHg or 70/50 mmHg and the heart rate decreased to 77 beats/min or 95 beats/min. The decrease in those parameters may enable to perform this surgery more easily. Since one of the cases had been suffering from ventral septal defect with patent ductus arteriosus, plastic surgery for septal defect was tried 2 months after the 1st surgery under ultrahypothermic anesthesia, however the patient died after the surgery. The other case showed a remarkable recovery with no clinical signs.
