Guidelines

Guidelines on Reptile Anesthesia Analgesia and Surgery

Unit for Laboratory Animal Medicine
Mar 15, 2016 12:00 am

This document has been designed by the ULAM veterinary staff as a guideline for sedation, anesthesia, and analgesia of laboratory reptiles. This is not intended to be an inclusive tutorial on all possible drug combinations that can be used in reptiles. The following guidelines are also general recommendations and consequently do not include reference to specific research associated concerns.

All surgical procedures, anesthetics, analgesics, antibiotics or other medications used on animals must be approved by the IACUC, described in the animal use protocol and performed by personnel listed on the protocol and appropriately trained for the surgical procedure. Any techniques or drug protocols deviating from this document must be justified and approved in the IACUC protocol prior to application.

  • Responsibility

    1. Principal Investigator: Responsible to ensure appropriate anesthesia, monitoring, and analgesia is provided for all animals undergoing surgical or sedation procedures.
  • Glossary Definitions

    Sedation

    Central depression causing stupor where the animal is unaware of its surroundings but still responsive to painful procedures.

    Immersion

    A method of delivering drugs via direct contact with the skin in a bath.

  • Procedures

    1. Anesthesia

    1. 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. Recovery may take several days. Anesthesia by hypothermia is unacceptable.
    2. Isoflurane is the preferred inhalant anesthetic due to its wide margin of safety. Other agents such as sevoflurane can also be used. Depth of anesthesia can be controlled if the reptile is intubated (use an uncuffed or uninflated endotracheal tube), the animal is ventilated with supplemental oxygen and the gas is administered by a precision vaporizer. The open drop technique (see Procedures section 1.e) may be used with isoflurane. Recovery from inhalant anesthesia is usually rapid. Some reptiles may be intubated with or without prior sedation or anesthesia, as their glottis and trachea are located rostrally and easily visualized. Two important things to remember when using inhalant anesthetics are 1) reptiles breathe due to LOW partial pressure of oxygen. Use of room air or air with less than 100% oxygen is advised when recovering an intubated reptile, to prevent prolonged recoveries that can be seen with pure oxygen. 2) reptiles can bypass standard metabolism requiring oxygen. Insufficient breathing on their own or regularly provided intermittent positive pressure ventilation (IPPV) can cause reptiles to utilize anaerobic respiration, causing the patient to not take in oxygen, and to not receive anesthesia. This results in an inappropriate plane of anesthesia and response to noxious stimuli such as cutting during surgery.
    3. Anesthesia induction, maintenance and recovery should be performed at the average or at the high end of the reptile's preferred body temperature range. If the range is not known for the particular species, 79° to 90°F is acceptable. Supplemental heat in the form of a recirculating warm water blanket should be provided during anesthesia, surgery, and recovery. Electric heating pads are discouraged due their increased risk for thermal injury. Regardless of the heat source, a towel or drape should be placed between the animal and the heat source to prevent burns. Fasting period in reptiles prior to anesthesia is variable, ranging from 2-4 hours in smaller reptiles to 24-72 hours in larger animals and 3-15 days in some snakes to promote ventilation as tidal volume is affected by visceral volume.
    4. For commonly used anesthesia protocols in reptiles (see Procedures section 6).
    5. Inhalant anesthetic agents by open drop technique - all species
      Isoflurane: 5-10 ml of isoflurane on cotton ball 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.
    6. Monitoring Anesthesia
      1. The following points may be helpful in monitoring anesthesia in reptiles:
        1. Muscle relaxation progresses from cranial (head) to caudal (tail) in the reptile; during recovery from anesthesia, motor function returns in reverse order.
        2. Loss of the righting reflex occurs as the depth of anesthesia increases.
        3. 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.
        4. Use of an electrocardiography monitor, a Doppler blood flow monitor or a pulse oximeter may be helpful.
        5. Monitoring heart sounds with a stethoscope is difficult in reptiles. Esophageal stethoscopes are easy to use and may aid in heart rate monitoring.
        6. Visualizing or palpating cardiac or respiratory movements may be difficult but should be attempted. 2-4 breaths per minute is adequate in most species.
        7. Corneal reflex remains present at a surgical depth of anesthesia in all reptiles except snakes, which have a spectacle covering their corneas.
        8. Tongue withdrawal reflex in snakes remains present at a surgical depth of anesthesia.
        9. The head and legs of turtles will not retract into the shell at a surgical plane of anesthesia.
      2. Post-anesthetic Care
        1. 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 0.2-0.6 ml/kg IV or IM will stimulate breathing in most reptiles. 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.

    2. Analgesia

    1. Signs of Pain: Signs of pain in reptiles can be difficult to monitor. Signs may include, but are not limited to, the following:
      1. Flinching, Muscle contractions, Attempts to bite, Anorexia, Lethargy, Weight loss, Color changes, Dull color, Ataxia / lameness, Decreases coiling at site of pain, Elevated respiratory rate, Social isolation, Biting at affected areas.
    2. Prevention and Management of Pain: 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, flunixin meglumine, and metacam have been used in reptiles for postoperative analgesia.
    3. Commonly used analgesic protocols
      1. Analgesic Agents - All Reptiles
        1. Opioids
          1. Buprenorphine
            1. 0.005-0.02 mg/kg IM every 24-48 hours
              1. When preemptive analgesia is used, consider reducing the dose of anesthetic (whether inhalant or injectable) to the low end of the recommended range. Anesthetic depth must be carefully monitored and drug doses may need to be titrated to maintain appropriate levels. With new projects, sexes, strains or anesthetic analgesic combinations, assess a subset of animals before expanding to use in a larger cohort.
        2. Non-Steroidal Anti-inflammatory Drugs (NSAIDs)
          1. Flunixin meglumine (Banamine)
            1. 0.1-0.5 mg/kg IM every 24-48 hours (maximum 3 days)
          2. Meloxicam (Metacam)
            1. 0.1-0.5 mg/kg PO, IM or SC every 24-48 hrs (maximum 3 doses)
        3. Local Anesthetics
          1. Lidocaine
            1. 2-5 mg/kg local infusion (maximum <5 mg/kg)
          2. Bupivicaine
            1. 1-2 mg/kg local infusion (maximum <4 mg/kg)

    3. Surgery

    1. Surgical Documentation
      1. See Appendix A below for a downloadable copy of a Reptile Surgery Record. This is a template but at a minimum laboratory surgical records must include the same necessary information: animal ID, PI, protocol number, surgeon, procedure, any analgesic or anesthetic drugs used (including dosage, route, and frequency of administration), and a pre-surgical evaluation.
    2. Preparation of the Surgical Area
      1. According to the Guide for the Care and Use of Laboratory Animals: Eighth Edition, "For most survival surgery performed on rodents and other small species...the space should be dedicated to surgery and related activities when used for this purpose, and managed to minimize contamination from other activities conducted in the room at other times." (pg. 144)
        1. The surgical area should be a room or a portion of a room that is easily sanitized and not used for any other purpose during the time of surgery.
        2. Clean and disinfect the surface upon which the surgery will be performed with an approved environmental disinfectant before beginning the surgical procedure.
        3. Use of clear plastic drapes provide a view of the reptile for assessment during surgery.
    3. Preparation of Surgical Supplies
      1. Surgical Instruments
        1. Use prepackaged aseptic surgical supplies whenever possible.
          1. Initial steam sterilization (autoclaving), plasma vapor sterilization, or ethylene oxide sterilization (for heat or pressure sensitive items) is required for all surgical instruments and items to be implanted
      2. Suture Materials and Incision Closure
        1. Incised reptile skin tends to invert, so closing skin in an everting pattern will aid in appropriate apposition of the skin edges and faster healing time.
        2. Suture materials such as nylon or polypropylene may be used to close surgical incisions. PDS, Vicryl, and skin staples (naturally evert skin) are often used.
        3. For internal suturing, absorbable suture material other than chromic catgut may be used
        4. Tissue adhesives (cyanoacrylate) may be used in some cases.
        5. Reptiles rarely bother incisions, so continuous patterns are appropriate in most cases.
        6. Absorbable suture material must be removed from cutaneous sites as absorption is prolonged.
        7. Suture removal should be performed 4-6 weeks after surgery or until appropriately healed (species variations), or may delayed until after ecdysis in those species that shed their skin.
        8. Hibernation should be prevented for at least 6 months to promote wound healing.
        9. Close any laparotomy site in two layers (muscle and skin) to prevent incisional dehiscence.
    4. Surgeon Preparation
      1. Wash hands thoroughly with a disinfecting soap such as chlorhexidine or iodine based surgical scrubs or 3M Avaguard® hand antiseptic.
      2. The surgeon must wear a mask, sterile or clean gloves, and a clean scrub top, clean disposable PPE gown, or clean lab jacket during the surgical procedure.
        1. Clean gloves include unused gloves stored in a sealable bag or container to minimize dust and debris contamination.
    5. Performing Multiple Surgeries in Series
      1. Investigators should begin with at least 2 sets of sterile instruments.
        1. Between animals, clean the instruments followed by disinfection with a hot bead sterilizer. Reptile skin is sensitive to thermal damage, so it is imperative that the instruments are allowed to cool prior to using them after hot bead sterilization.
        2. No more than 5 animals should be used per pack of sterile instruments.
      2. New clean or sterile gloves should be used for each animal.
      3. The surgical area should be cleaned with an appropriate disinfectant between animals.

    4. Post-Operative Recovery, Monitoring and Care

    1. Animals must be visibly observed and monitored every 15 minutes during recovery from anesthesia until the animal is ambulatory and exhibiting species-specific behaviors.
    2. Post-Operative Documentation
      1. Tanks/enclosures containing animals that have undergone surgery must be labeled. Laboratory staff is to use ULAM acetate system (unless approved by the IACUC to use otherwise) and affix a yellow acetate with a Surgery Observation Sticker (SOS) to the tank. The label or acetate will be kept on the enclosure for at least at least 4 weeks; until skin sutures or wound clips are removed (if applicable); or the animal is euthanized; whichever is longer.
        1. The date of surgery and end date of monitoring must be recorded on the sticker.
        2. Wound clips, staples or skin sutures must be removed within 4 - 6 weeks (provided the skin incision is adequately healed) unless described otherwise in the IACUC-approved protocol or as recommended by a ULAM veterinarian to necessitate complete wound healing. Adequate healing is described as apposed wound edges without signs of dehiscence, increased redness, discharge, odor or overt swelling.
      2. Post-operative monitoring and health status of the animals must be recorded during the post-operative monitoring period and records must be maintained in the post-surgical documentation.
        1. Attached to this document is a Reptile Anesthetic, Surgical and Post-Operative Monitoring record (see Appendix A). Laboratory staff may use this template, or develop and use their own system/template.
        2. Animals must be examined all post at least once a day for 14 days, and then at the minimum of once weekly for at least another 2 weeks, or until wound healing is achieved; the skin sutures or wound clips are removed (if applicable); or the animal is euthanized; whichever is longer.
        3. Records must contain - at a minimum - the following information:
          1. The Principal Investigator name and Protocol
          2. The animal species, strain, and animal ID
          3. The surgeon(s) name(s), the date of surgery, and the surgical procedure
          4. The doses and routes of administration for all drugs administered (anesthetics, analgesics, etc.)
            1. *For as needed analgesic therapy - If the animal is not showing clinical signs of pain, this must be documented in the record during the post-monitoring period (e.g., "No clinical signs of pain observed, analgesics not administered.")
          5. Post-surgical notes on the animal's recovery, and observation notes that may include comments on animal condition, surgical site, drugs administered, etc.
          6. Date of end of monitoring indicating such
        4. Records must be stored in the animal room until the end of the month of post-op monitoring. Laboratory staff will place all surgical records (or copies thereof) at the drop box in the animal holding room. At the end of the month, husbandry staff clips all surgical records in the drop box and submits the compiled documents to the building husbandry supervisor who then purges the records after a year of maintenance.
        5. For more information, see Guidelines on Medical Records for Investigative Personnel.

    5. Commonly used sedation protocols for reptiles

       Drug   

       Dosage (mg/kg)   

       Route   

       Comments   

       Chelonians   

       

       

       

       Midazolam   
       1.5 - 2.0   
       IM, SC   
    • Mild sedation, inconsistent effects alone, useful as preanesthetic and increases efficacy of ketamine.
    • Most species, not painted turtles.   
       Dexmedetomidine (D)*   
       + Midazolam (M)   
       0.025 - 0.1 (D)   
       + 1.0 (M)
       IM, SC   
    • Mild to moderat sedation.   
    • Completely reversible.   
       Dexmedetomidine (D)*   
       + Midazolam (M)   
       + Ketamine (K)   
       0.025 - 0.1 (D)   
       + 1.0 (M)   
       + 2.5 - 5.0 (K)   
       IM, SC   
    • Moderate to deep sedation.   
    • Partially reversible.   
       Dexmedetomidine (D)*   
       + Ketamine (K)   
       0.025 - 0.07 (D)   
       + 5.0 - 10.0 (K)   
       IM, SC, IV   
    • Deep sedation to light anesthesia.   
    • Partially reversible.   
       Propofol   
       2.0 - 5.0   
       IV   
    • Moderate sedation to light anesthesia.   

       Lizards   

       

       

       

       Dexmedetomidine (D)   
       + Midazolam (M)   
       0.05 - 0.1 (D)   
       + 1.0 (M)   
       IM, SC   
    • Moderate sedation.   
    • Completely reversible.   
       Dexmedetomidine (D)   
       + Midazolam (M)   
       + Ketamine (K)   
       0.05 - 0.1 (D)   
       + 1.0 (M)   
       + 2.5 - 5.0 (K)
       IM, SC   
    • Deep sedation, can be used for minor surgery if used with local anesthesia.
    • Partially reversible.   
       Propofol   
       3.0 - 5.0   
       IV, IO   
    • Deep sedation to light anesthesia.   

       Snakes   

       

       

       

       Midazolam   
       1.5 - 2.0   
       IM, SC   
    • Minimal sedation, inconsistent effects.
    • Completely reversible.   
       Telazol   
       2.0 - 5.0   
       IM, SC   
    • Mild to moderate sedation, intubation.   
    • For use on large snakes.   
       Ketamine   
       5.0 - 10.0   
       IM, SC   
    • Mild to moderate sedation, intubation.   
    • Decreases incidence of breath-holding during chamber induction.   
       Propofol   
       3.0 - 5.0   
       IV   
    • Moderate sedation to light anesthesia.   
    • First choice for induction agent.   

    Use lower dose (D) in tortoises and higher dose in water turtles

    6. Commonly used anesthetic protocols in reptiles

       Drug   

       Dosage (mg/kg)   

       Route   

       Comments   

       Chelonians   

       

       

       

       Dexmedetomidine (D)*   
       + Midazolam (M)   
       + Ketamine (K)   
       + Hydromorphone (H)   
       0.025 - 0.05 (D)   
       + 0.5 (M)   
       + 2.0 - 10.0 (K)   
       + 0.5 (H)   
       IM, SC   
    • Surgical anesthesia.   
    • Deepen with inhalant anesthesia.   
    • Partially reversible.   
       Dexmedetomidine (D)*   
       + Morphine (M)   
       + Ketamine (K)   
       0.025 - 0.1 (D)   
       + 1.5 (M)   
       + 5.0 - 20.0 (K)   
       IM, SC   
    • Surgical anesthesia.   
    • Partially reversible.   
       Dexmedetomidine (D)*   
       + Ketamine (K)   
       0.05 - 0.15 (D)   
       + 5.0 - 20.0 (K)   
       IM, SC, IV   
    • Surgical anesthesia.   
    • Partially reversible.   
       Propofol   
       2.0 - 20.0   
       IV   
    • Induction agent, use lower dose in large tortoises.   
    • Can maintain with 1.0 mg/kg/min when inducing with 5 - 10 mg/kg   
       Isoflurane   
       2 - 5%
       
    • Induction at 5%, maintenance at 2 - 3%   
       Sevoflurane   
       2.5 - 8%
       
    • Induction at 7 - 8%, maintenance at 2.5 - 4.5%   

       Lizards   

       

       

       

       Propofol   
       5.0 - 10.0   
       IV, IO   
    • Induction agent, lower end of dose can last 20 - 30 minutes.   
    • Can maintain with 0.25 mg/kg/min.   
       Isoflurane   
       2 - 5%   
       
    • Induction at 5%, maintenance at 2 - 3%   
       Sevoflurane   
       2.5 - 8%   
       
    • Induction at 7 - 8%, maintenance at 2.5 - 4.5%   
       Ketamine   
       5 - 10   
       IM   
    • Decreases the incidence of breath holding during induction with an inhalant agent.
       Dexmedetomidine (D)   
       + Ketamine (K)   
       0.05 - 0.07 (D)   
       + 5.0 - 15.0 (K)   
       IM, SC, IV   
    • Partially reversible.   

       Snakes   

       

       

       

       Propofol   
       3.0 - 10.0   
       IV, IO   
    • Induction agent, lower end of dose can last 20 - 30 minutes.   
    • Can maintain with 0.25 mg/kg/min.   
       Isoflurane   
       2 - 5%   
       
    • Induction at 5%, maintenance at 2 - 3%   
       Sevoflurane   
       2.5 - 8%   
       
    • Induction at 7 - 8%, maintenance at 2.5 - 4.5%   
       Ketamine   
       5 - 10   
       IM   
    • Decreases the incidence of breath holding during induction with an inhalant agent.
       Telazol   
       2.0 - 6.0   
       IM   
    • Induction agent, helps with intubation.   
    • Maintain with an inhalant agent.   
    • Prolonged recoveries likely.   

    Use lower dose (D) in tortoises and higher dose in water turtles

    7. Commonly used reversal agent protocols - Chelonians, Lizards, & Snakes

       Drug   

       Dosage (mg/kg)   

       Route   

       Comments   

       Atipamazole   

       10X demedetomidine dose in mg   

       SC, IV, IP   

       ** Give same volume as dexmedetomidine administered.   

       Flumazenil   

       0.05   

       SC, IV, IM   

       13:1 midazolam:flumazenil (mg)   

       Naloxone   

       0.04   

       SC, IM   

       

     

  • Appendix A: Reptile Surgery Record

  • References

    1. Bennett RA. Anesthesia. In: Reptile Medicine and Surgery, DR Mader, WB Saunders Co., 1996, pp 241-247.
    2. Bennet RA and DR Mader. Soft Tissue Surgery. In: Reptile Medicine and Surgery, DR Mader, WB Saunders Co., 1996, pp 287-291.
    3. Carpenter JW.Chapter 4: Reptiles. In: Exotic Animal Formulary, Elsevier Inc., 2013, pp 100-111.
    4. Carpenter JW. Pharmacotherapeutics in Reptiles: An Update and Review. In: Proceedings of 31st Annual Conference of the World Small Animal Veterinary Association, Prague, Czech Republic, pg. 321.
    5. Pye G, Carpenter J. Ketamine Sedation followed by Propofol Anesthesia in a Slider, Trachemys scripta, to Facilitate Removal of an Esophageal Foreign Body Assoc Reptilian Amphibian Vet 81:16-171998
    6. Divers SJ. et al. Pharmacokinetics of meloxicam following intravenous and oral administration in green iguanas (Iguana iguana). AJVR, 2010; 71:11, pp 1277-1283.
    7. Guzman, DSM. Reptile Analgesia and Anesthesia. Wildlife and Aquatic Animal Medicine Club Symposium, 2013.
    8. Martin, BJ. Evaluation of hypothermia for anesthesia in reptiles and amphibians. ILAR Journal, 1995; 37:4, pp 186-190.
    9. Mosely, C. Topics in Medicine and Surgery: Anesthesia and Analgesia in Reptiles. In: Seminars in Avian and Exotic Pet Medicine, Vol 14, No 4 (October), 2005: pp 243-262.
    10. Page CD. Current Reptilian Anesthesia Procedures. In: Zoo and Wild Animal Medicine: Current Therapy 3, ME Fowler WB Saunders Co., 1993, pp 140-143.
    11. Schumacher J. Reptiles and Amphibians. In: Lumb and Jones' Veterinary Anesthesia, Third Edition, eds. JC Thurmon., WJ Tranquilli and JE Benson, Williams and Wilkins, 1996, pp. 670-682.
    12. Sladky, K. and C. Mans. Topics in Medicine and Surgery: Clinical Anesthesia in Repties. In: Journal of Exotic Pet Medicine, Vol 21, 2012, pp 17-31.
Questions?

If you have questions or comments about this document, contact ULAM Veterinary Staff (ULAM-vets@umich.edu or 734-936-1696).

The ULAM Training Core (ULAM-trainingcore@umich.edu or 734-763-8039) can be contacted to provide training in techniques at no charge.

For any concerns regarding animal health after work hours or on holidays/weekends, contact DPS (3-1131) who will contact the on-call veterinarian.