INTRAMUSCULAR EPINEPHRINE RESULTS IN REDUCED ANESTHETIC RECOVERY TIME IN AMERICAN ALLIGATORS (ALLIGATOR MISSISSIPPIENSIS) UNDERGOING ISOFLURANE ANESTHESIA

Abstract

Inhalants are commonly used to anesthetize reptiles, but volatile anesthetics have been associated with prolonged recovery times. The objective of this study was to determine the effects of intramuscular (IM) epinephrine on anesthetic recovery times following isoflurane anesthesia in a population of subadult American alligators ( Alligator mississippiensis ). In this prospective randomized crossover study, five clinically healthy alligators were anesthetized for 90 min with the use of isoflurane. Alligators were randomly assigned into one of two treatment groups: Group E received IM epinephrine (0.1 mg/kg), and Group S received an equal volume of 0.9% saline administered after isoflurane was discontinued. Time from the end of inhalant administration to return of spontaneous ventilation, return of the palpebral reflex, movement in response to a standardized toe pinch, and spontaneous movement was recorded. The time of extubation was noted and occurred following the return of spontaneous ventilation and movement. Pulse rate, surface body temperature, and airway gases including expiratory and inspiratory isoflurane concentrations and end-tidal carbon dioxide were measured every 5 min throughout the study. The time from the end of anesthesia to extubation was significantly faster in Group E (51.2 ± 16.7 min) compared to Group S (107.4 ± 43.7 min). Pulse rate was significantly higher within the first 15 min following epinephrine injection compared to the saline group at these time points. Therefore, IM epinephrine administered at the end of general anesthesia can significantly hasten anesthetic recovery from isoflurane in alligators.

Elimination of Intracardiac Shunting Provides Stable Gas Anesthesia in Tortoises

“…Isoflurane anesthesia can increase the vagal tone 29 and create vasodilation which consequently decreases systemic vascular resistance 30 , both circumstances that could trigger a R-L shunt 8 , 12 – 14 , 31 . Exposure to the gas during induction likely also triggered apnea, a condition that further promotes R-L shunts 15 .…”

Ectothermy and cardiac shunts profoundly slow the equilibration of inhaled anaesthetics in a multi-compartment model

“…Other potential support for Q tot and potentially reducing right-to-left shunts could include the use of a β-agonist, such as dobutamine, via increasing cardiac contractility and rate. This will have contributed to the finding that adrenaline administration hastened recovery from inhaled anaesthesia in alligators and chelonians [45][46][47] . However, large doses of adrenaline may also compromise perfusion and Q tot due to the increase in vascular resistance and cardiac afterload given adrenaline's α effects 32 .…”

The Influence of Movement on the Cerebrospinal Fluid Pressure of the American Alligator (Alligator mississippiensis)

“…The majority of this variation is due to two factors. Firstly, the anesthesia protocol developed in the lab (which produced the traces in Figure 2 ) was designed to safely achieve and maintain a surgical plane of isoflurane anesthesia [ 32 , 53 ], it was not designed to replicate the mechanics of active breathing in A. mississippiensis . Secondly, this species has some of the most variable ventilatory mechanics of any vertebrate.…”

“…The alligators were maintained on a steady ventilatory pattern of 5 breaths per minute each with a tidal volume of 500 mL. Anesthesia was accomplished using 5% isoflurane [ 32 ]. Two silver chloride surface cup electrodes (019-477200, GRASS, Natus Medical, Pleasanton, CA, USA), coated with a layer of conducting gel (Signagel, Parker Laboratories, Fairfield, NJ, USA) were placed on the lateral surface of the animal, on either side of the heart, and the EKG signal recorded (at 4 kHz) using a MiDAS (Xcitex Inc., Woburn, MA, USA) data acquisition system.…”

“…(3) with the animal still under anesthesia it was tilted 30° head-up and 30° head-down (separately), each over a 90 s duration divided into 30 s baseline, 30 s tilt, then 30 s recovery. (4) the animal was allowed to recover from anesthesia, this is a slow (hours-long) process in alligators [ 32 ]; the animal was actively ventilated with oxygen during recovery, but no drugs were administered to accelerate recovery. (5) while the animal was still anesthetized, the straps restraining the tail were removed and the distal tip of the tail was manually wiggled from side to side.…”