anestesia guia

Guidelines for Anesthesia, Postanesthetic Care and Surgery of Reptiles

Prepared by the ULAM Veterinary Staff

September 27, 1996

Introduction

This document is intended to provide guidelines on anesthesia, postanesthetic care and surgery to investigators who anesthetize or perform surgery on reptiles. Sources of additional information are listed at the end of the document.

Anesthesia

Anesthesia in reptiles may be performed using injectable or inhalant anesthetic agents. Injectable anesthetics are relatively easy to administer, but once given, the effects are prolonged and may be unpredictable. Induction may be prolonged, as well as recovery, which may take up to several days.

Inhalant anesthetics include isoflurane, halothane and methoxyflurane. If the reptile is intubated and a precision vaporizer is used to administer the gas, the depth of anesthesia is controlled, supplemental oxygen is being administered, and the animal can be ventilated. The open drop technique (see page 3) may be used with methoxyflurane. Recovery from inhalant anesthesia is usually rapid. Some reptiles may be intubated with or without prior sedation or anesthesia.

Hypothermia is not recommended for anesthesia although it may aid in immobilization.

Anesthesia induction, maintenance and recovery should be performed within the reptile’s preferred temperature range. If the range is not known for the particular species, 79^o to 90^oF is acceptable. Reptiles should be fasted for 24-48 hours prior to anesthesia to promote ventilation as tidal volume is affected by visceral volume.

Monitoring Anesthesia

The following points may be helpful in monitoring anesthesia in reptiles:

·Muscle relaxation progresses from cranial to caudal in the reptile; during recovery from anesthesia, motor function returns in reverse order.

·Loss of the righting reflex occurs as the depth of anesthesia increases.

·Mucous membrane color may be used to assess oxygen perfusion and cardiac output, but this may be misleading in species which do not normally have pink mucous membranes.

·Use of an electrocardiography monitor, a Doppler blood flow monitor or a pulse imeter may be helpful. Monitoring heart sounds with a stethoscope is difficult in reptiles.

·Visualizing or palpating cardiac or respiratory movements may be difficult but should be attempted. 2-4 breaths per minute is adequate in most species.

·Corneal reflex remains present at a surgical depth of anesthesia in all reptiles except snakes, which do not have a cornea.

·Tongue withdrawal reflex in snakes remains present at a surgical depth of anesthesia. ·The head and legs of turtles will not retract into the shell at a surgical plane of anesthesia.

Postanesthetic care

The reptile should be maintained in a clean, warm, dark environment. The temperature and humidity should be at the upper end of the optimum range for the species. During recovery, the reptile may be stimulated by a toe or tail pinch, causing the animal to move and to take a breath. Doxapram at 5 mg/kg IV or IM may be used to stimulate respiration. The reptile should be monitored closely for at least 24 hours after recovery from anesthesia. Frequent monitoring may be necessary for several days if an injectable anesthetic agent is used.

Surgery

Although some deviations from strict aseptic procedures are considered acceptable for reptile surgery, most of the basics of aseptic technique should be observed when performing surgery on reptiles. The surgical site in reptiles may be sterilized with povidone-iodine or chlorhexidine solution, followed by ethanol. Chlorhexidine provides the advantages of broader spectrum of activity and increased residual activity. Use of clear plastic drapes provide a view of the reptile for assessment during surgery. As with other species, sterile gloves and instruments should be used for surgical procedures.

For internal suturing, absorbable suture material other than chromic catgut may be used. Suture materials such as nylon or polypropylene may be used to close surgical incisions. Since incised reptilian skin tends to invert, skin incisions should be closed with an everting suture pattern to promote apposition of cut edges and healing. Absorbable suture material must be removed from cutaneous sites as absorption is prolonged. Suture removal should be performed 4-6 weeks after surgery, or may delayed until after ecdysis in those species that shed their skin.

Hibernation should be prevented for at least 6 months to promote wound healing.

Analgesia

Although pain and pain relief in reptiles is not well understood, it may be advisable to use analgesic agents in reptiles that have undergone a potentially painful procedure. Buprenorphine and flunixin meglumine have been used in reptiles for postoperative analgesia.

Injectable Anesthetic Agents

Turtles and Tortoises Ketamine HCl ·20-60 mg/kg IM rapid induction; prolonged recovery; lower doses for sedation to facilitate endotracheal intubation. Tiletamine HCl and zolazepam HCl ·10-20 mg/kg IM; most suitable for sedation to facilitate endotracheal intubation.

Lizards Tiletamine HCl and zolazepam HCl ·30 mg/kg IM produces surgical anesthesia with rapid induction time; recovery may be prolonged.

Snakes Ketamine HCl ·50-130 mg/kg IM rapid induction; prolonged recovery, may need to assist respiration at higher dose, lower dose for preanesthetic sedation. Tiletamine HCl and zolazepam HCl ·10-20 mg/kg IM; most suitable for sedation to facilitate endotracheal intubation. Methohexital sodium ·5-15 mg/kg IM, SC induction and recovery times rapid.

Inhalant Anesthetic Agents by Open Drop Technique

All species Methoxyflurane ·10 ml methoxyflurane in a 10 gallon aquarium in a fume hood; should only be used for single exposure which provides 10-30 minutes of surgical anesthesia; reptile must not contact anesthetic agent.

Injectable Analgesic Agents

All reptiles Buprenorphine ·0.005-0.02 mg/kg IM every 24-48 hours. Flunixin meglumine ·1.0 mg/kg IM every 24 hours.