Anesthesia & analgesia in birds

Transcription

1 Anesthesia and analgesia in birds Yvonne R.A. van Zeeland, DVM, PhD, MVR, Dip. ECZM (avian) Division of Zoological Medicine, Utrecht University Anesthesia & analgesia in birds Yvonne van Zeeland DVM, MVR, PhD, Dip. ECZM (avian) Internacionalizace výuky veterinární medicíny jako cesta na evropský trh práce projekt è. CZ.1.07/2.2.00/ Brno, Czech Republic March 4, 2014 Division of Zoological Medicine Department of Clinical Sciences of Companion Animals Faculty of Veterinary Medicine, Utrecht University Introduction Indications for anesthesia Indications for anesthesia Analgesia Anesthetic agents Injectable anesthesia Inhalation anesthesia Airsac perfusion anesthesia Post-anesthetic considerations Surgical intervention Soft tissue surgery Orthopedic surgery Sedation - minor procedures Stress reduction Immobilizat ion Examples Physical examination Blood collection Diagnostic imaging Bandaging Pre-anesthetic fasting Pre-emptive analgesia Supportive care Stabilize FIRST (if needed) Length of procedure Less important for short procedures (<30 min) More preparations needed for longer procedures 1

2 Evaluate from a distance Less stressful Evaluation from a distance Physical examination Evaluation from a distance Physical examination Obtain accurate weight Evaluation from a distance Physical examination Obtain accurate weight Additional diagnostic work-up Mostly for longer procedures PCV & blood chemistry Anemia, dehydration, kidney or liver failure? Evaluation from a distance Physical examination Obtain accurate weight Additional diagnostic work-up Handling may compromise patient Remember: in some patients, handling may be more compromising than a short period of anesthesia Pre-anesthetic fasting Crop needs to be empty Gentle aspiration optional if fasting is impossible Risk of hypoglycemia is minimal Recommendations: Birds < 200 g BW => no fasting (max. 1-2 hrs) Psittacines g BW => 4-6 hrs Raptors => 6 24 hrs (until pellet is produced) 2

3 Analgesia Pre-emptive analgesia (before pain occurs!) Local anesthetics Lidocaine < 4 mg/kg Bupivacaine < 2 mg/kg SAIDs / Corticosteroids Not often used (immunosuppression) NSAIDs (also chronic & postoperative pain) Carprofen 2 4 mg/kg Meloxicam mg/kg Ketoprofen 5 mg/kg Opioids (acute pain) Butorphanol mg/kg Buprenorphine 0.5 mg/kg At least 30 min. prior to anesthesia! Injectable anesthesia Less controllable than inhalation anesthesia Inability to modify or reverse effect after administration Commonly used drugs: Medetomidine µg/kg 400 µg/kg IM Xylazine 10 mg/kg Ketamine 30 mg/kg 50 mg/kg IM Butorphanol 1 mg/kg 2 mg/kg IM Carprofen 4 mg/kg Meloxicam mg/kg 0.5 mg/kg SC Alternative: ketamine (60 mg/kg) + diazepam (2 mg/kg) + NSAID Inhalation anesthesia Generally considered safer Better to regulate depth of anesthesia Halothane Not often used due to side-effects Less safe than newer inhalant anesthetics Isoflurane vs. sevoflurane Sevoflurane is: Much more expensive, BUT Quicker induction and recovery +/- Premedication (butorphanol + midazolam) Reduces stress and lowers MAC Induction Procedure Use a face mask or induction chamber to anesthetize the bird Induction: 4-5% isoflurane in 100% oxygen (1 L/min) Procedure Intubation Pressure under the tongue to visualize the glottis Assisted ventilation To prevent CO 2 accumulation in the distal air sacs, assisted ventilation is mandatory! Manual versus mechanically assisted breathing Do NOT cuff!! (birds have closed tracheal rings) Careful with small birds (tube sizes mm): blockage/bending Fixate tube with tape to upper or lower beak Maintenance: 2% isoflurane in 100% oxygen (1 L/min)! 3

4 Air sac perfusion anesthesia Peri-anesthetic considerations Prevent dehydration Fluid therapy Prevent heat loss Active and passive heating More extensive information is provided during lecture on soft tissue surgery Peri-anesthetic considerations Fluid therapy Prevent dehydration Fluid therapy Prevent heat loss Active and passive heating vital functions Respiration Cardiovascular system Body temperature Routes of administration Subcutaneous Intravenous Intraosseus Type of fluids Crystalloids Colloids Oxygen carriers Volumes SC boluses of 50 ml/kg IV or IO: 10 ml/kg/hr Routes of administration Subcutaneous route Large volumes at once Prior to or after anesthesia Not stressful Twolocations Between shoulder blades Inguinal space Routes of administration Right jugular vein Largest vessel Mainly for boluses Crystalloids 10 ml/kg Colloids 5 ml/kg Basilic vein Medial metatarsal vein Intravenous route 4

5 Routes of administration Intraosseus catheters Higher core body temperature & metabolism Accessible in most species Locations Ulna Tibiotarsus Humerus and femur NOT to be used in birds! Connected to airsacs Heat loss occurs through Convection Airflow around the patient Radiation Difference between temperature patient and its surroundings Conduction Contact with colder surface Evaporation Through respiration & opening of coelom Solutions Cover patient & minimize plucking Heat loss occurs through Convection Airflow around the patient Radiation Difference between temperature patient and its surroundings Conduction Contact with colder surface Evaporation Through respiration & opening of coelom Solutions Cover patient & minimize plucking Work in a warm, preheated room Provide heating source Hydrate anesthetic gasses Drape patient a.s.a.p. E.g. Aluminum foil (not always practical) (not practical) (not practical) 5

6 Bag with rice => microwave Bag with rice => microwave Hotpacks Bag with rice Hotpacks Warm water blankets Bag with rice Hotpacks Warm water blankets Bair Hugger Anesthetic plane Evaluation of anesthetic plane 5 stages Reflexes present Reflexes absent Physiologic parameters Remarks Bag with rice Hotpacks Warm water blankets Bair Hugger Hot dog I. Induction All: palpebral, pedal, None Sedate, lethargic; cere; voluntary Drooping of eyelids; movement 3 rd eyelid Deep or shallow breathing II. All None; Arousable but no resistance eyes closed Increased 3 rd eyelid movement III. Light Palpebral/pedal/cer e Voluntary movement Breathing rapid, regular, deep present but slow; lacking; no response No response to sound corneal, withdrawal; to postural changes Some jaw tone present pain on plucking IV. Medium Corneal reflex present Palpebral/pedal/cere/ Good muscular relaxation Surgical but sluggish withdrawal; no pain Slow, deep, regular respiration on plucking Little jaw tone V. Deep None; lack of corneal All Slow, shallow, intermittent respiration Pupillary dilation. Excitatory phase may occur; more likely in large birds Preferred plane for minor, non-painful procedures Preferred plane for surgery Death ensues, emergency! 6

7 Capnography Intubation is necessary CO 2 levels 2-4 mm H 2 O Capnography Temperature Normal C Keep above 38.0 C Capnography Temperature Pulse Oximetry Capnography Temperature Pulse Oximetry Doppler 7

8 Emergency protocols Post-anesthetic considerations Emergency situation Treatment Apnea - Intubate (if not already done) - Turn off anesthetic gas or reverse injectable anesthetics - Intermittent positive pressure ventilation (IPPV) - Doxapram 5-20 mg/kg IM/IV/IO/IT; repeat in 2 min Endotracheal tube blockage Hypovolemia (shock if >30%) - Remove tube and replace if necessary - Provide100% O2, reduceanesthetic gas if recovery is feasible - Use of pre-emptive anticholinergics is controversial - Volume replacement with warmed isotonic fluids, colloids, or blood - Preferably IV or IO Regurgitation - Hold head down to drain liquid, clean oral cavity - Suction endotracheal tube and consider replacement of tube Hypothermia (<38 C) - Increase thermal support Bradycardia, cardiac arrest - Discontinue or reverse anesthetics - Atropine (0.5 mg/kg IM/IV/IO/IT) in case of bradycardia - Adrenaline (0.5-1 mg/kg IM/IV/IO) in case of cardiac arrest - Alternatekeel compression andcaudalcoelomic compression Monitoring does NOT stop once surgery is over and patient is awake! Continued monitoring of patients is mandatory (Antagonize to reverse anesthesia) Keep warm Keep hydrated Provide food as soon as possible Provide proper level of analgesia Questions??? Thank you for your attention! 8