11. Rodent and Rabbit Anesthesia

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  • A geriatric hamster can be as young as 18 months old. These “old” animals can present geriatric anesthetic risks. Don’t transfer a rabbit (prey) in a carrier that has been previously used for cat (predator) transport. Wear clothing (lab coat) that hasn’t been worn when handling dogs and cats.
  • Rabbits should never be lifted by their ears.
  • The intraosseous route for administering fluids is a good means of providing prolonged fluid therapy in rabbits, guinea pigs, and rats.
  • The ocular reflexes are not as useful in small mammals as they are in the dog and cat.
  • ECG machines are not suitable to use on small rodents because of their fast heart rate and low-amplitude signals generated.
  • 11. Rodent and Rabbit Anesthesia

    1. 1. Rodent and Rabbit Anesthesia Chapter 11
    2. 2. Patient Evaluation <ul><li>Difficult to obtain accurate information </li></ul><ul><li>Shorter life spans </li></ul><ul><li>Physical examination </li></ul><ul><ul><li>Transport to clinic </li></ul></ul><ul><ul><li>Observe normal behavior and respiratory pattern before handling </li></ul></ul><ul><ul><li>Safe and humane restraint </li></ul></ul>
    3. 3. Handling and Restraint <ul><li>Mouse </li></ul><ul><ul><li>Pick up by base of the tail </li></ul></ul><ul><ul><li>Rest on forearm for external examination </li></ul></ul><ul><ul><li>Rest on rough surface for administration of injectables </li></ul></ul><ul><ul><li>Injection sites </li></ul></ul>
    4. 4. Handling and Restraint (Cont’d) <ul><li>Rat </li></ul><ul><ul><li>Nocturnal animals; awaken before handling </li></ul></ul><ul><ul><li>Pick up around shoulders or lift by base of tail </li></ul></ul><ul><ul><li>Rest on forearm, restrain by tail or around shoulders </li></ul></ul><ul><ul><li>Injection sites </li></ul></ul>
    5. 5. Mouse Restraint
    6. 6. Mouse Injections
    7. 7. Rat Restraint
    8. 8. Rat Injections
    9. 9. Handling and Restraint <ul><li>Hamster </li></ul><ul><ul><li>Temperament differences </li></ul></ul><ul><ul><li>Nocturnal animal; awaken before handling </li></ul></ul><ul><ul><li>Gentle and secure restraint </li></ul></ul><ul><li>Gerbil </li></ul><ul><ul><li>Very active; can easily escape </li></ul></ul><ul><ul><li>Be careful of skin on tail </li></ul></ul><ul><li>Guinea Pig </li></ul><ul><ul><li>Immobile to agitated </li></ul></ul><ul><ul><li>Swift and firm restraint </li></ul></ul>
    10. 10. Hamster Restraint
    11. 11. Hamster Injection
    12. 12. Guinea Pig Restraint
    13. 13. Handling and Restraint <ul><li>Rabbits </li></ul><ul><ul><li>Breed variations </li></ul></ul><ul><ul><li>Support back; animals kick with hind legs </li></ul></ul><ul><ul><li>Lift by skin over shoulders; support abdomen </li></ul></ul><ul><ul><li>Injection sites </li></ul></ul>
    14. 14. Rabbit Restraint
    15. 15. Small Mammal Physical Examination <ul><li>Observe in transport box for undisturbed behavior </li></ul><ul><li>Respiratory rate and pattern probably elevated </li></ul><ul><li>Palpate or auscultate the heart rate </li></ul>
    16. 16. Small Mammal Physical Examination (Cont’d) <ul><li>Abnormalities </li></ul><ul><ul><li>Discharges from eyes and noses </li></ul></ul><ul><ul><li>Labored/noisy respiration </li></ul></ul><ul><ul><li>Soiled perineum </li></ul></ul><ul><ul><li>Sunken eyes indicating dehydration </li></ul></ul><ul><ul><li>Prominence of vertebrae and pelvis indicating poor body condition </li></ul></ul><ul><ul><li>Rabbit: prolonged capillary refill time </li></ul></ul>
    17. 17. Small Mammal Preanesthetic Diagnostic Tests <ul><li>Blood tests </li></ul><ul><ul><li>Rabbits </li></ul></ul><ul><li>Urinalysis </li></ul><ul><ul><li>Small rodents, rabbits, guinea pigs </li></ul></ul><ul><li>Radiography </li></ul><ul><ul><li>Small rodents, rabbits, guinea pigs </li></ul></ul>
    18. 18. Preanesthetic Care <ul><li>Don’t withhold food and water </li></ul><ul><ul><li>Except when stomach is involved in surgery </li></ul></ul><ul><ul><li>Must reestablish feeding as soon as possible after surgery </li></ul></ul><ul><ul><li>Don't feed during the day </li></ul></ul><ul><ul><ul><li>Many animals are nocturnal </li></ul></ul></ul><ul><ul><li>Pain and discomfort can decrease appetite </li></ul></ul><ul><li>Correct preexisting problems </li></ul><ul><ul><li>Supportive fluid therapy for dehydration </li></ul></ul><ul><ul><ul><li>IV, SC, IP, or intraosseous routes </li></ul></ul></ul>
    19. 19. Preanesthesia <ul><li>Sedation is rarely needed prior to general anesthesia </li></ul><ul><ul><li>Protocols include a combination of injectable anesthetic agents or use of a chamber </li></ul></ul><ul><ul><li>Rabbits may need prior sedation </li></ul></ul>
    20. 20. Preanesthesia (Cont’d) <ul><li>Preanesthetics are used: </li></ul><ul><ul><li>Atropine </li></ul></ul><ul><ul><ul><li>Reduce salivation and bronchial secretions </li></ul></ul></ul><ul><ul><ul><li>Don’t use in rabbits </li></ul></ul></ul><ul><ul><li>Opioid analgesics </li></ul></ul><ul><ul><ul><li>30-40 minutes prior to induction </li></ul></ul></ul><ul><ul><ul><li>Provides preemptive analgesia </li></ul></ul></ul><ul><ul><li>Sedatives or tranquilizers </li></ul></ul><ul><ul><ul><li>Given to rabbits prior to inhalation anesthesia </li></ul></ul></ul>
    21. 21. Preanesthetic Agents <ul><li>Anticholinergics </li></ul><ul><ul><li>Atropine and glycopyrrolate </li></ul></ul><ul><li>Phenothiazines </li></ul><ul><ul><li>Acepromazine </li></ul></ul><ul><ul><ul><li>Sedates but does not immobilize rodents </li></ul></ul></ul><ul><ul><ul><li>Sedates rabbits and often provides enough immobilization for minor procedures </li></ul></ul></ul><ul><li>Benzodiazepines </li></ul><ul><ul><li>Diazepam and midazolam </li></ul></ul><ul><ul><ul><li>Marked sedation in rodents and rabbits </li></ul></ul></ul>
    22. 22. Preanesthetic Agents (Cont’d) <ul><li>Alpha 2 -agonists </li></ul><ul><ul><li>Xylazine, medetomidine, and dexmedetomidine </li></ul></ul><ul><ul><ul><li>Sedation with some analgesia </li></ul></ul></ul><ul><ul><li>Higher dose may provide immobilization </li></ul></ul><ul><ul><li>Side effects </li></ul></ul><ul><ul><ul><li>Same as in dogs and cats except vomiting </li></ul></ul></ul><ul><ul><li>Reverse with yohimbine or atipamezole (preferred) </li></ul></ul>
    23. 23. Preanesthetic Agents (Cont’d) <ul><li>Opioids </li></ul><ul><ul><li>Provide preemptive analgesia </li></ul></ul><ul><ul><li>Commonly used in combination with sedative agents </li></ul></ul><ul><ul><ul><li>Acepromazine and butorphanol helpful to get blood samples from rabbits </li></ul></ul></ul>
    24. 24. General Anesthesia: Induction <ul><li>Rabbits </li></ul><ul><ul><li>SC or IM routes most common </li></ul></ul><ul><ul><li>IV may be possible </li></ul></ul><ul><li>Small mammals </li></ul><ul><ul><li>IP route less painful than IM route </li></ul></ul><ul><li>IP or IM vs. IV route of administration </li></ul><ul><ul><li>Cannot administer drug to effect </li></ul></ul><ul><ul><li>One calculated dose is given </li></ul></ul><ul><ul><li>High dose rates are required for proper depth </li></ul></ul><ul><ul><li>Recovery times are prolonged </li></ul></ul>
    25. 25. General Anesthetic Agents: Cyclohexamine Agents <ul><li>Ketamine </li></ul><ul><ul><li>Limited effect in small mammals when used alone </li></ul></ul><ul><ul><li>Provides restraint in rabbits but not sufficient analgesia </li></ul></ul><ul><ul><li>Ketamine/acepromazine and ketamine/diazepam or midazolam: produces surgical anesthesia in some rabbits and light anesthesia in small rodents </li></ul></ul><ul><ul><li>Ketamine/alpha 2 -agonist (medetomidine or xylazine): provides analgesia and surgical anesthesia </li></ul></ul><ul><ul><ul><li>Variable results in guinea pigs </li></ul></ul></ul><ul><ul><ul><li>Monitor anesthetic depth carefully </li></ul></ul></ul>
    26. 26. General Anesthetic Agents: Cyclohexamine Agents (Cont’d) <ul><li>Tiletamine </li></ul><ul><ul><li>Combined with zolazepam (Zoletil, Telazol) </li></ul></ul><ul><ul><ul><li>Light-to-medium anesthesia in small rodents </li></ul></ul></ul><ul><ul><li>Produces less analgesia than ketamine combinations </li></ul></ul>
    27. 27. General Anesthetic Agents: Neuroleptanalgesics <ul><li>Neuroleptic (droperidol, fluanisone) combined with analgesic (fentanyl) </li></ul><ul><ul><li>Provides restraint and analgesia in small mammals </li></ul></ul><ul><ul><li>Must combine with a benzodiazepine to produce surgical anesthesia </li></ul></ul><ul><ul><li>Recovery enhanced by reversing fentanyl </li></ul></ul>
    28. 28. General Anesthetic Agents <ul><li>Barbiturates in small mammals </li></ul><ul><ul><li>Narrow safety margin </li></ul></ul><ul><ul><li>Severe cardiovascular and respiratory depression </li></ul></ul><ul><ul><li>Prolonged recovery </li></ul></ul><ul><ul><li>May be administered IV to rabbits </li></ul></ul><ul><li>Propofol </li></ul><ul><ul><li>Small rodents </li></ul></ul><ul><ul><ul><li>Not used because it must be administered IV </li></ul></ul></ul><ul><ul><li>Rabbits </li></ul></ul><ul><ul><ul><li>Short period of light anesthesia for ET intubation and gas anesthesia </li></ul></ul></ul>
    29. 29. General Anesthetic Agents (Cont’d) <ul><li>Alphaxalone </li></ul><ul><ul><li>Steroid anesthetic </li></ul></ul><ul><ul><ul><li>Induces anesthesia in rabbits </li></ul></ul></ul><ul><ul><li>Administered IV </li></ul></ul>
    30. 30. Inhalation Anesthetics: Small Mammals <ul><li>Anesthetic chamber is the most convenient method to induce anesthesia </li></ul><ul><ul><li>Appropriate size </li></ul></ul><ul><ul><li>Fill from bottom; excess gases removed from top </li></ul></ul><ul><li>Isoflurane, desflurane, and sevoflurane used in small rodents </li></ul><ul><ul><li>Rapid induction; rapid recovery </li></ul></ul><ul><ul><li>Deliver with precision vaporizer into chamber </li></ul></ul><ul><ul><li>Maintain with face mask </li></ul></ul><ul><ul><li>Scavenge waste gas </li></ul></ul>
    31. 31. Anesthetic Induction Chamber
    32. 32. Inhalation Anesthetics: Rabbits <ul><li>Rabbits often hold their breath when exposed to inhalation agents </li></ul><ul><ul><li>May lead to bradycardia </li></ul></ul><ul><ul><li>Using face mask may lead to struggling </li></ul></ul><ul><ul><li>Using chamber may result in violent attempts to escape </li></ul></ul><ul><li>Preanesthetic agents are preferred prior to induction </li></ul><ul><ul><li>Less struggling but may still hold breath </li></ul></ul><ul><ul><li>Induce general anesthesia with face mask </li></ul></ul>
    33. 33. Intubation of Rabbits and Small Rodents <ul><li>Rabbits </li></ul><ul><ul><li>Uncuffed ET tubes and laryngoscope with blade or canine otoscope </li></ul></ul><ul><ul><li>Larynx is visualized or blind technique </li></ul></ul><ul><li>Small rodents </li></ul><ul><ul><li>Nasal catheter positioned in back of pharynx </li></ul></ul><ul><ul><li>Does not allow for assisted ventilation </li></ul></ul><ul><ul><li>Waste gases removed by extract tube close to nose </li></ul></ul>
    34. 34. Nasal Catheter
    35. 35. Monitoring Anesthesia <ul><li>Out-of-circuit vaporizer </li></ul><ul><li>Open, nonrebreathing system </li></ul><ul><li>Fresh gas flow rates </li></ul><ul><li>Depth of Anesthesia </li></ul><ul><ul><li>Small rodents </li></ul></ul><ul><ul><ul><li>Tail pinch and pedal withdrawal </li></ul></ul></ul><ul><ul><li>Rabbits and guinea pigs </li></ul></ul><ul><ul><ul><li>Ear pinch reflex </li></ul></ul></ul>
    36. 36. Anesthetic Delivery in a Rabbit
    37. 37. Monitoring Anesthesia <ul><li>Heart rate and rhythm </li></ul><ul><ul><li>Rabbits and guinea pigs </li></ul></ul><ul><ul><ul><li>Auscultate chest wall, palpate chest wall, esophageal stethoscope (rabbit) </li></ul></ul></ul><ul><ul><li>Small rodents </li></ul></ul><ul><ul><ul><li>Palpate chest wall </li></ul></ul></ul><ul><li>Capillary refill time </li></ul><ul><ul><li>Rabbits only </li></ul></ul>
    38. 38. Monitoring Anesthesia (Cont’d) <ul><li>Blood loss </li></ul><ul><ul><li>Small mammals have a small total blood volume </li></ul></ul><ul><ul><li>Monitor blood loss carefully </li></ul></ul><ul><li>Arterial blood pressure </li></ul><ul><ul><li>Rabbits only </li></ul></ul><ul><ul><li>Catheter in central ear artery, oscillometric technique, or Doppler probe </li></ul></ul>
    39. 39. Blood Pressure Monitoring and Pulse Oximeter Probe
    40. 40. Monitoring Anesthesia <ul><li>Respiratory rate and depth </li></ul><ul><ul><li>Observe chest movements; no reservoir bag </li></ul></ul><ul><ul><li>Normal rates during anesthesia </li></ul></ul><ul><ul><ul><li>Small rodents 50-100 bpm; rabbits 30-60 bpm </li></ul></ul></ul><ul><ul><li>50% drop in bpm requires attention </li></ul></ul><ul><li>Pulse oximetry </li></ul><ul><ul><li>Need monitor with upper limit 350 bpm </li></ul></ul><ul><ul><li>Place across hind foot in small rodents </li></ul></ul><ul><ul><li>Place across a toe in large rabbits </li></ul></ul><ul><ul><li>Tail, tongue, and ear can also be used </li></ul></ul>
    41. 41. Pulse Oximeter Probe
    42. 42. Monitoring Anesthesia <ul><li>Capnography </li></ul><ul><ul><li>Side-stream vs. mainstream capnographs </li></ul></ul><ul><li>Thermoregulation </li></ul><ul><ul><li>Increased ratio of surface area to body weight </li></ul></ul><ul><ul><li>Rapid cooling during anesthesia </li></ul></ul><ul><ul><li>Monitor rectal temperature with electronic thermometer </li></ul></ul><ul><ul><li>Shave a minimal surgical site </li></ul></ul><ul><ul><li>Place animal on a warming pad </li></ul></ul><ul><ul><li>Warm fluids prior to administration </li></ul></ul><ul><ul><li>Continue warming during the recovery period </li></ul></ul>
    43. 43. Postoperative Care <ul><li>Recovery area </li></ul><ul><ul><li>95º F (35º C) while animal is unconscious </li></ul></ul><ul><ul><li>79º F-81º F (26º C-28º C) after animal is conscious </li></ul></ul><ul><ul><li>Warm comfortable bedding (synthetic sheepskin) </li></ul></ul><ul><ul><li>Encouraged to eat ASAP </li></ul></ul><ul><ul><li>Provide water in familiar container </li></ul></ul><ul><ul><li>SC or IP warmed fluids (98.6º F or 37º C) </li></ul></ul><ul><ul><li>Postoperative analgesia </li></ul></ul>
    44. 44. Anesthetic Emergencies <ul><li>Respiratory depression </li></ul><ul><ul><li>Determine cause </li></ul></ul><ul><ul><li>Intubated </li></ul></ul><ul><ul><ul><li>Check ET tube placement; administer 100% oxygen </li></ul></ul></ul><ul><ul><li>Not intubated </li></ul></ul><ul><ul><ul><li>Extend head and neck and gently compress chest </li></ul></ul></ul><ul><ul><li>Small rodents </li></ul></ul><ul><ul><ul><li>Place soft rubber tubing or syringe barrel over nose and mouth and blow gently to inflate lungs </li></ul></ul></ul><ul><ul><li>Administer doxapram </li></ul></ul>
    45. 45. Assisting Ventilation in a Rat
    46. 46. Anesthetic Emergencies <ul><li>Circulatory failure </li></ul><ul><ul><li>IV fluid therapy </li></ul></ul><ul><ul><ul><li>SC and IP routes provide minimum benefits </li></ul></ul></ul><ul><ul><li>Blood transfusion from donor animal </li></ul></ul><ul><ul><li>Plasma volume expander </li></ul></ul><ul><li>Cardiac arrest </li></ul><ul><ul><li>External cardiac massage </li></ul></ul><ul><ul><li>Emergency drugs at appropriate dose rate and volume </li></ul></ul>
    47. 47. Postoperative Analgesia <ul><li>Pain assessment obstacles </li></ul><ul><ul><li>Nocturnal animals </li></ul></ul><ul><ul><li>Fear or threat response to humans by going immobile </li></ul></ul><ul><li>Procedure for undisturbed animals </li></ul><ul><ul><li>Observe abnormal posture or hunched body </li></ul></ul><ul><ul><li>Look for hair coat that is unkempt and ruffled with piloerection </li></ul></ul><ul><ul><li>Rats: black discharge from eyes and nose </li></ul></ul><ul><ul><li>Animal positioned at back of cage or buried in bedding </li></ul></ul>
    48. 48. Postoperative Analgesia (Cont’d) <ul><li>Procedure for disturbed animals </li></ul><ul><ul><li>Encourage the animal to move and observe gait or posture and the presence of aggression </li></ul></ul><ul><ul><li>Apathy or aggression when handled </li></ul></ul><ul><ul><li>Vocalization (or no vocalization) and biting </li></ul></ul><ul><ul><li>Immobility </li></ul></ul><ul><li>Monitor food and water intake by monitoring body weight </li></ul>
    49. 49. Analgesic Agents <ul><li>Opioids </li></ul><ul><ul><li>Shorter duration of action </li></ul></ul><ul><ul><li>Buprenorphine preferred, 6-12 hours of action </li></ul></ul><ul><ul><li>Other drugs may require repeated doses </li></ul></ul><ul><ul><li>Combine with NSAID </li></ul></ul><ul><li>Nonsteroidal antiinflammatory drugs </li></ul><ul><ul><li>Carprofen, ketoprofen, meloxicam </li></ul></ul><ul><ul><li>Prolonged duration of action, 12-24 hours </li></ul></ul><ul><ul><li>Monitor long-term use for side effects </li></ul></ul>
    50. 50. Analgesic Agents (Cont’d) <ul><li>Local anesthetics </li></ul><ul><ul><li>Infiltrated around surgical wounds or specific nerve blocks </li></ul></ul><ul><ul><li>Narrow margin of safety; calculate dose carefully </li></ul></ul><ul><ul><li>Shorter duration of action </li></ul></ul><ul><ul><li>Topical agents used for venipuncture or IV catheter placement </li></ul></ul><ul><li>Chronic pain </li></ul><ul><ul><li>Arthritis, dental disease, neoplasia </li></ul></ul><ul><ul><li>NSAIDs most successfully used; monitor long-term use </li></ul></ul>
    51. 51. Administration of Analgesics <ul><li>IV administration </li></ul><ul><ul><li>Difficult in small rodents; straightforward in rabbits </li></ul></ul><ul><li>IM administration </li></ul><ul><ul><li>Rodents have small muscle masses </li></ul></ul><ul><li>SC </li></ul><ul><ul><li>Preferred route for rodents </li></ul></ul><ul><li>Oral </li></ul><ul><ul><li>May require firm physical restraint </li></ul></ul><ul><ul><li>Can be added to highly palatable food if animal is eating </li></ul></ul>
    52. 52. Analgesia and Postoperative Rules of Thumb <ul><li>Don’t recover small mammals in the same room as their predators </li></ul><ul><li>Preemptive analgesia administration is usually more effective than postoperative administration </li></ul><ul><li>Opioids administered prior to inhalation anesthesia can reduce the amount of inhalant anesthetic needed </li></ul>
    53. 53. Analgesia and Postoperative Rules of Thumb (Cont’d) <ul><li>Preemptive analgesia is more difficult when injectable anesthetics are used </li></ul><ul><li>If opioids are being used as the analgesic with injectable anesthetics, the opioids should be administered at the end of the anesthetic period </li></ul><ul><li>Not all NSAIDs can be used safely preoperatively because of their effects on the kidney and bleeding times </li></ul>

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