Rapid, safe, and effective methods of anesthetic induction and recovery are needed for sea turtles (for review, see Chittick et al., 2002), especially in cases eligible for immediate release.1 Free-ranging sea turtles undergoing laparoscopy for population biology studies have traditionally not received general anesthetics or sedative analgesics due to concerns over potential mortality following a return to water. We hypothesized that intravenous propofol would provide rapid induction of anesthesia in loggerhead sea turtles (Caretta caretta) with rapid recovery, allowing safe return to water shortly after the procedure. This study investigates the effects of propofol on anesthetic depth and physiology as part of a larger study involving the validation by laparoscopy of a hormonal sex determination assay in juvenile loggerheads.
Forty-nine loggerhead sea turtles were recovered as local fishery bycatch in pound nets and transported to a surgical suite. Treatment animals (n=32) received 5 mg/kg propofol IV, whereas control animals (n=17) received no propofol. For analgesia, all animals received a 4-ml infusion of 1% lidocaine into the site of incision, as well as 2 mg/kg ketoprofen IM. Turtles were placed in head-down recumbency or right-lateral recumbency to facilitate laparoscopic access to the reproductive organs. Physiologic data included heart and respiratory rate, temperature, and a single blood gas sample collected upon termination of the laparoscopy. Subjective data included jaw tone, ocular reflex, and pedal withdrawal scores: 3 (vigorous) to 0 (none detected). Anesthetic depth was scored from 1 (no anesthesia) to 3 (surgical anesthesia). The turtle was observed until it appeared alert and was then returned to water for overnight observation before release the following day.
Turtles receiving propofol became apneic for a minimum of 5 minutes, with a mean time of 13.7±8.3 minutes to the first respiration. Limb movement returned at a mean time of 21.1±16.8 minutes. The treatment animals were judged to be sedated (anesthetic depth score ≥1.5) when compared to controls for approximately 30 minutes. Mean respiratory rates for treatment animals were slower compared to controls for the first 14 minutes, then after 35 minutes, became significantly faster than the controls. Mean heart rates of treatment animals were significantly higher than controls between 40 and 44 minutes.
Physiologic differences between groups remained for at least 1 hour. Possible explanations for these differences include a compensatory recovery of treatment animals from anesthesia-induced hypoxia and hypercapnia or, alternatively, a stress response of the non-sedated control animals. The animals induced with propofol were easier to secure to the restraint device and moved less during laparoscopy. In conclusion, propofol is a safe and effective injectable anesthetic for use in wild loggerhead sea turtles that provides for a rapid induction and recovery.
We would like to thank Aleta Hohn and her fabulous staff at NOAA NMFS, especially Larisa Avens, Lisa Goshe, and April Goodman, as well as Wendy Cluse, Nicole Mihnovets, and Shane Christian, and Drs. Mathew Godfrey, Priscilla Joyner and Conny Gunkel, and the many NCSU veterinary student volunteers for facilitating this project.
1. Chittick, E.J., M.A. Stamper, J.F. Beasley, G.A. Lewbart, and W.A. Horne. 2002. Medetomidine, ketamine, and sevoflurane for anesthesia of injured loggerhead sea turtles: 13 cases (1996–2000). J. Am. Vet. Med. Assoc. 221:1019–1025.