Cardiopulmonary effects of prolonged anesthesia via propofol-medetomidine infusion in ponies

Objective-To determine cardiopulmonary effects of total IV anesthesia with propofol and medetomidine in ponies and effect of atipamezole on recovery. Animals-10 ponies. Procedure-After sedation was induced by IV administration of medetomidine ( 7 mug/kg of body weight), anesthesia was induced by IV administration of pr opofol (2 mg/kg) and maintained for 4 hours with infusions of medetomidine (3.5 mug/kg per hour) and propofol (0.07 to 0.11 mg/kg per minute). Spontan eous respiration was supplemented with oxygen. Cardiopulmonary measurements and blood concentrations of propofol were determined during anesthesia. Fi ve ponies received atipamezole (60 mug/kg) during recovery. Results-During anesthesia, mean cardiac index and heart rate increased sign ificantly until 150 minutes, then decreased until cessation of anesthesia. Mean arterial pressure and systemic vascular resistance index increased sig nificantly between 150 minutes and 4 hours. In 4 ponies, PaO2 decreased to <60 mm Hg. Mean blood propofol concentrations from 20 minutes after inducti on onwards ranged from 2.3 to 3.5 <mu>g/ml. Recoveries were without complic ations and were complete within 28 minutes with atipamezole administration and 39 minutes without atipamezole administration. Conclusions and Clinical Relevance-During total IV anesthesia of long durat ion with medetomidine-propofol, cardiovascular function is comparable to or better than under inhalation anesthesia. This technique may prove suitable in equids in which prompt recovery is essential; however, in some animals severe hypoxia may develop and oxygen supplementation may be necessary.