–Deepened clinical exam
–Therapeutic procedure (ex: oesophagostomy tube)
–Risk of anesthetic death is 1.4% in rabbits, 3.8% in GP, 1.7 to 3.7% in other exotics. Much more important than in dogs and cats (6-10x)
–Do not exceed 5 to 10%, around 2 to 5ml/kg
–An average gauze sponge will absorb 7ml of fluids
–An average coton tip applicator will aborb 0,17ml of fluids
–Factors to control:
–Species identification is mandatory, especially in birds and reptiles
–Stress (prey species!)
–Subclinical nutritional deficiencies (calcium, vitamin A, vitamin C)
–Subclinical diseases, esp. respiratory diseases (rabbits, rats) causing hypoxia. Thoracic Xrays and Bloodwork are advised.
–Small diameter of trachea: obstruction with fluids, edema or unadapted position
–Herbivores have usually smaller thorax compared to abdomen volume
–Peroperative complications: hypothermia (high surface area to body volume ratio)
–Postoperative complications such as digestive problem, infection, pain, electrolyte imbalances
–IV catheterization, IV fluids, tracheal intubation are not systematics
Recovery from anesthesia is obtained when the patient is able to stand up on his legs, to move when stimulated, to maintain a sternal body position with normal respiratory, cardiac parameters. They require specific attention until they eat alone, and can maintain normally their body temperature.
–Should I keep the water bowl or water bottle in the cage?
–Does he need to eat? Should I let extruded diets? Hay?
–Provide secure and hidden area so the patient will not be too anxious
–What is the POTZ (or PBT=Preferred Body Temperature) of this Reptile?
–Was he examined by a vet of the structure recently?
What is required for a safe anesthesia?
2.Prepare your material
What is our knowledge of anesthesia in exotic species?
–A lot of different species. Something that works and is weel-tolerated by rabbits may be toxic and dangerous in another species…
–A lot of publications and range of dosages,
–Not the same safety level when you are looking on anesthetic dosages used in experimentation and in clinical practice.
–How to chose? Respect the vet’s experience and the patients needs.
General information about Anesthesia
–Influenced by the drugs and species, strain, age, sex, body condition, type of procedure
–Always adjust to your patient: it is called TITRATION.
–Depends on the procedure (if painful, a deeper anesthesia is usually needed)
–Depends on the dosage of the anesthetic molecule (% of anesthetic gas or dosage of chemical anesthesia)
–It only brings NARCOSIS (amnesia, loss of consciousness and immobility)
–The preferred way to anesthetize exotic pets. It does not mean that they are used alone. They are always associated to other drugs bringing analgesia, muscle relaxation or sedation (midazolam-morphine).
–Exotics: Isoflurane >> Sevoflurane. Don’t use Halothane (very toxic for humans and pets).
–% of anesthetic gas permits to adjust the depth and duration of anesthesia.
–Dose-dependent cardiovascular depression
–Non-rebreathing or pediatric circle
–Low dead space and low resistance
–Nose-cone, mask or tracheal tube
–Birds: Possible to use an air-sac catheter
–Protect yourself: do not breath that gas. Ventilate the room, reduce the loss of gas (mask’s size), adapt the % of oxygen and gas to the patient (do not overdose) and check the scavenging (outside or through activated charcoal canisters).
–Induction: preferably in a sedated patient (otherwise, struggling and breath-holding), in a small box, a big mask or directly with towel handling. First, preoxygenation during several minutes, then 2 to 5 minutes with 3 to 5% isoflurane gas. Reduce gas % once the anesthetic state is obtained. Stress, apnea, hypotension and bradycardia can occur.
–Maintenance: 1,5 to 3,5% depending of the preanesthetic drugs, the type of procedure, the species…
–Recovery: only oxygen until complete recovery. Check breathing pattern, cardiac frequency and temperature. Hypotension and hypothermia are common. Be sure of airways patency.
–Never use an injectable molecule alone. Associate it to other injectable anesthesia or to gaseous anesthesia (Combination drug= cocktail anesthesia).
–Difficult to adjust: once injected, it can not be removed. Some molecules (alpha2 agonist like medetomidine and dexmedetomidin) can be reversed with atipamezole. If needed, can be re-administered (20 to 30% of the initial dosage) but it decreases the safety level (however, we can not finish the procedure if the animal is not properly anesthetized).
The first injection must be done before surgery, it is called « pre-emptive analgesia ». It permits to block the painful stimuli.
–What about atropine and glycopyrrolate?
How to secure anesthesia?
–Always check airways patency (extend the neck so the trachea is straight)
–Air sac catheterization is possible in birds
–They are very sensitive to food deprivation (hypoglycemia, transit slow down).
–If anesthesia is required for a short duration and non invasive procedure (grooming, diagnotic, dental): remove food only 1h before anesthesia to ensure there is no more food in the oral cavity and crop.
–If anesthesia is required for a longer duration and more invasive procedure (abdominal surgery): remove food only 3h before anesthesia in rabbits and rodents.
Prepare all the material needed for the anesthesia, the procedures and a potential emergency
Check particularly the anesthetic circuit (level of isoflurane, open-circuit, production of oxygen)
–Depth of anesthesia:
–Cornea should be lubricated to prevent drying out
–IV line when possible and fluids i possible
–Atropine, adrenaline, glycopyrrolate, doxapram, diazepam should be ready to use with syringe, needles and tables showing dosage by species and weight
–Laryngeal mask are great, if weel-inserted, to oxygenate patients. They permit to realize positive-pressure ventilation if needed.
–It is also possible to ventilate via the mask if adequately sealed or to blow gently into the nose
Gastric tympanism may develop
–In 1 survey, more than half the anesthetic mortalities occurred after the surgery!
–Heart rate, Respiratory Rate and Airways patency, Body temperature should be monitored regularly.
–The patient must benefit of oxygen delivery until his complete recovery (except Reptiles!)
–When recovered: appetite and feeding, fecal output, pain, behavior should be supervised
–Painkiller should be used in a pre-emptive manner
–Assisted feeding are required in birds and small mammals
–Prokinetics drugs should be used in herbivores species
–Do not forget social contact when they need it