Isoflurane-remifentanil Anesthesia in 14 Dogs with Congenital Extrahepatic Portosystemic Shunts Undergoing Surgical Ligation

Abstract

Animals with portosystemic shunts have decreased liver function and thus reduced drug metabolism and excretion capacity, resulting in delayed recovery from general anesthesia. In this study, a balanced anesthesia protocol using isoflurane inhalation and constant rate infusion of remifentanil was investigated, as both these drugs do not depend on the liver for metabolization or excretion. The study included owner-owned 14 dogs diagnosed with congenital extrahepatic portosystemic shunts. During the surgeries, remifentanil infusion at 18-42 μg/kg/h and end - expiratory isoflurane concentrations with a range 0.77-1.19 % allowed smooth completions of surgical procedure for shunt ligations in all cases. The median concentrations of serum ammonia and total bile acid decreased significantly from preoperative values of 130 μg/dl (16-304) and 73.6 μmol/l (6.3-441.1) to postoperative values of 49 μg/dl (11-135) (p = 0.0295) and 24.4 μmol/l (2.6-97.9) (p = 0.0058), respectively. Complication incidence observed during general anesthesia were hypotension (86 %), hypothermia (57 %), tachycardia (36 %) and hypocapnia (7%). Postanesthetic complications observed within the first 48 hours were neurological symptoms (50 %), gastrointestinal symptoms (29%) and urinary tract symptoms (7 %). The mean duration of hospitalization after surgery was 7 days (4-14 days) with no obvious anesthesia-related complications. Our study showed that a balanced anesthesia protocol of isoflurane and remifentanil could be safely used in canine patients with reduced liver functionality without causing serious anesthesia-related complications.