Printed in Brazil ANESTHESIA AND ANALGESIA IN ANTARCTIC FISH: AN EXPERIMENTAL APPROACH*

It was studied in Antarctic fishes the anesthetic and/or analgesic actions of central depressors ketamine, fentanyl and thiopental as well as the local anesthetic benzocaine. The drugs were added to aerated marine water at temperatures of 1-1.5 C. Ketamine (15 mg/L) and fentanyl (50 g/L) failed in inducing anesthesia but caused a long lasting analgesia and sedation. Thiopental was required in doses of 100 mg/L to anesthetize the fishes, that is, about 30 times higher than the usual anesthetic dose for mammals. The anesthesia was long lasting, that is, 3-4 h, and difficult to control. One fish remained in a comatose state for four days with survival. Benzocaine in doses of 100 mg/L was successful in anesthetizing the fishes within 6-8 min, anesthesia lasting for 15-20 min, with a minor respiratory depression.