Medetomidine, Ketamine, and Sevoflurane Anesthesia in Loggerhead Sea Turtles (Caretta caretta)
The cardiopulmonary effects of medetomidine, ketamine, and sevoflurane anesthesia were evaluated in six juvenile loggerhead sea turtles (Caretta caretta) presented to the North Carolina State University College of Veterinary Medicine for trauma-related injuries between 1996 and 1999. Turtles were induced with 50 µg/kg medetomidine (Pfizer Animal Health, Exton, PA) and 5 mg/kg ketamine (Fort Dodge Animal Health, Fort Dodge, IA) intravenously in the dorsal cervical sinus, intubated, and maintained on sevoflurane (Abbott, N. Chicago, IL) at 0.5–2.0%. An ADS 1000 ventilator (Engler Engineering Corporation, Hialeah, Florida) was used to provide a respiratory rate of 2–4 breaths/min and peak inspiratory pressure of 15–18 cm H2O. The dorsal cervical sinus was catheterized with a 1610-2P Mila catheter with guidewire (Mila International, Florence, KY). Parameters monitored included induction and recovery times, heart rate and rhythm, temperature, end tidal CO2, and venous blood gas parameters. At the end of each procedure, medetomidine was reversed with 0.25 mg/kg atipamezole (Pfizer Animal Health, Exton, PA) intravenously.
The mean (±SD) induction time was 8.8±3.9 min. The combination of medetomidine and ketamine provided adequate jaw and glottis relaxation to facilitate endotracheal intubation. Anesthesia times ranged from 110–325 min. Recovery times from discontinuation of sevoflurane to extubation ranged from 5–124 min and from administration of atipamezole to extubation, 0–84 min. Mean (±SD) recovery time from sevoflurane discontinuation was 62.0±40.4 min (median 65.0 min), while mean (±SD) recovery time from atipamezole administration was 24.3±31.5 min (median 14.0 min). No arrhythmias were noted. Heart rates ranged from 10–20 beats/min and temperatures from 23.5–26.5°C. Baseline (Mean±SD) venous blood gas values in four sea turtles were: pH 7.48±0.06, PCO2 39±5 mm Hg, PO2 25±8 mm Hg, and HCO3 34.1±4.0 mmol/L. After 140 min of anesthesia in four turtles, venous blood pH ranged from 7.53–7.69, PO2 from 9–58 mm Hg, PCO2 from 15–29 mm Hg, and HCO3 from 27.1–33.0 mmol/L. Respiratory alkalosis was likely due to ventilator settings above 2 breaths/min in these animals. Intraoperative end tidal CO2 values were lower than venous CO2, suggestive of significant shunting of pulmonary blood. The combination of medetomidine, ketamine and sevoflurane appears to be a safe and effective anesthetic protocol providing relatively short induction and recovery times in loggerhead sea turtles.
Reprinted with permission: Proceedings of the 20th Annual Symposium on Sea Turtle Biology and Conservation. 2000. Orlando, Florida.