Anesthesia in birds and exotic pet animals

Anesthesia in Birds and Exotic Pet animals

Presented byGanga Prasad Yadav

M.V.Sc.Veterinary Surgery & Radiology

Indications for anesthesiaRestraining and SedationDiagnostic Imaging - X-ray and UltrasoundSurgical procedures - Fracture repair and Growth removalTransportationControl of convulsion - SeizureCapturing of exotic animalsEuthanasia

General considerations For Anesthesia

Pre-anesthetic considerations1. Discussion with Owner.2. Reduce the animal’s stress.3. Pre-surgical evaluation and

animal selection a. Physical examination - Quiet observation - Contraindication to anesthesia

b. Laboratory evaluation -Complete CBC, biochemical profile (minimum: PCV, TP, BUN and Glucose). c. Diagnostic evaluation - X-ray - Ultrasound - ECG - Endoscopy etc.

Pre-anesthetic Fasting Necessary to prevent regurgitation.In birds, when fasting is impossible, Crop

needs to be empty.Due to high metabolic rate,

hypoglycemia in very small birds and exotic pet animals.

Time period for pre-anesthetic food with drawl in birds and exotic animals

Types of animal Time(hour)Birds <100 gram 0Large psittacine birds 1 to 2Raptor, Ratite, waterfowl 12 to 24Carnivores reptile ingesting whole prey

> 5 days

Reptile < 200 gram 2 to 4 Reptile 200 to 500 gram 12Reptile > 500 gram 24+Fish 12-24Rodent < 200 gram 0-2 Rodent > 200 gram >6Guinea pig 6-8Ferret 3-6Rabbit 0-24

• Maintaining homeothermy- Small animals are predisposed to

hypothermia due to high surface area to volume ratios.

- Ectotherms (Reptiles and Fish).- Core body temperature Digital/esophageal/rectal or cloacal

thermometer used.- Heat sources: incubator, warm air blanket

etc.

• Fluid therapy - Administer if anesthetic procedure more than 20 minutes. - 10-20 ml/kg body weight per hour during anesthesia. - Preheated fluid to 26-35° C for animals weighting less than 1 kg and for all ectotherm.

Sites for Parenteral access or Injections in birds and exotic pets

Species SitesBirds IM, IO, Jugular and Medial metatarsalRat and Mouse SQ, IM, IP, IO, IV, Jugular and Lateral tailGerbil SQ, IM, IP, IO, IV, Lateral tail, Saphenous and Metatarsal

Hamster SQ, IM, IP, IO (Tibial crest), IV, Lateral tarsus, Cephalic and Lingual

Chinchilla SQ, IM, IP, IO, IV, Jugular, Cephalic, Tail, Lateral saphenous

Rabbit: SQ, IM, IP, IO (trochanteric fossa), IV, Marginal ear vein, Jugular and Cephalic, Lateral saphenous

Guinea pig SQ, IM, IP, IO (trochanteric fossa). IV, Marginal ear vein, Jugular and lateral Saphenous veins

Ferret SQ, IM, IP, IO, IV, cephalic, jugular, lateral saphenous and lateral tail

Note: IM, Intramuscular; IO, Intraosseus; IP, Intraperitoneal; IV, Intravenous and SQ, Subcutaneous

Oxygen Supply • Necessary in Respiratory compromised or anaemic patients.• Facemask.• Endotracheal tube: Cuffless tube is used.• Air sac canulation in birds: if surgery of head, trachea or syrinx.

Figure: air sac canulation in bird

Fig.: ET tubes Fig.: Epiglottis in raptor

Premedication in birdsIndications :1. Restraining2. Sedation3. Analgesia4. muscle relaxation5. Reduce drugs required for

induction and maintenance6. Smooth recovery etc.

Preanesthetic sedatives and other drugs are rarely used in birds with exception of analgesics (eg. Butorphanol) due to stress from handling.

Anticholinergic drugs such as atropine and glycopyrrollate are not routinely used to birds because thickened respiratory tract secretions increase the risk of airway or endo-tracheal tube occlusion. Used only if history of bradycardia.

Local Anesthesia in Birds

To provide analgesia.Lignocaine@<4 mg/kg. Toxic dose of local anesthesia

(Lignocaine) is approximately ≥4 mg/kg.

Bupivacaine: 2mg/kg at the site of incision or as ring block provide 4 hours of analgesia.

Injectable sedatives, anesthetics and analgesic drugs used in birds

drugs dosesAtropine 0.01-0.02 mg/kg IV, 0.02-0.08 mg/kg IM

Glycopyrrolate 0.01-0.02 mg/kg IV, IM

Buprenorphine 0.01-0.10 mg/kg IM

Butorphanol 0.1-4.0 mg/kg IM

Fentanyl 0.2mg/kg IM

Diazepam 0.05-0.15mg/kg IV, 0.2-0.5mg/kg IM

Midazolam 0.05-0.15mg/kg IV, 0.1-0.5 mg/kg IM (7mg/kg intranasally)

Detomidine 12mg/kg intranasally

Ketamine < 1kg: 30-40mg/kg im; >1kg: 15-20 mg/kg im

Ketamine/midazolam 20-40mg/kgIM+4mg/kgIM

Ketamine/xylazine 10-30mg/kg IM+2-6mg/kg IM

Propofol 10mg/kg slow iv infusion until effective, upto 3mg/kg maintenance doses

Flunixin meglumine 1-10mg/kg iv, im

carprofen 2-10mg/kg IM, 1 mg/kg SQ

Inhalent Anesthesia in Birds

Used for both induction and maintenance. Isoflurane is currently the anesthetic choice

although Sevoflurane is excellent but more expensive.

Induction and maintenance at 3% to 4% and 1% to 2.5% respectively for Isoflurane and 4% to 6% and 3% to 4% respectively for Sevoflurane.

Oxygen flow rate of 150 to 200 ml/kg/min but 1L/min in most medium and large birds (approximately >300 grams).

Monitoring of anesthesia

• By monitoring heart rate, respiratory rate and temperature.

• Anesthetic monitoring equipments can be useful and includes

ECG machine Pulse Oximeter Capnograph Doppler flow detector.

Figure: ECG leads in bird

Recovery of Patient • Keep warm.• Keep hydrated.• Provide food as

soon as possible after recovery.• Maintain analgesia

for couple of days. Fig.: bird is in incubator during recovery phase

Anesthetic emergencies

1. Apnea 2. Blocked Endotracheal tube 3. Cardiac arrest4. Depression of respiratory rate during a long period of anesthesia

Anesthesia in ReptileHistory and Physical examinationLaboratory evaluation: CBC, PCV,

BUN, Uric acid and Glucose.Other evaluations (dehydration, anemia

and acid base imbalance) must be corrected prior to anesthetic induction.

Although regurgitation and aspiration is unlikely, fasting is recommended because of impaired digestion.

Preanesthetics in Reptiles

Preanesthetics are rarely indicated, except in large, aggressive, and/or venomous reptiles. Anticholinergics make respiratory secretions more viscous. Intubation is similar to birds. Oxygen flow rate @ 1L/0.3-1kg; 1L/5-10 kg for larger reptiles.

Premedication and analgesic drugs used in reptile

Induction anesthesia

drugs dosepropofol 5-10mg/kg iv, ic in snakes

10 mg/kg iv, io in lizards12-15 mg/kg iv in chelonian10-15 mg/kg iv in crocodilia

ketamine 20-60 mg/kg im5-15 mg/kg iv, io

Tiletamine/zolazepam

10-40 mg/kg im in squamates5-15 mg/kg im in chelonians and crocodilians

Inhalants are commonly used, using clear plastic chamber.IV injection of anesthetics is not generally practical in these species but induction via IM injection can be carried out using pole syringes or blow pipes.Propofol IV induction.

Figure showing induction by face mask

in Gecho

Fig.: Clear plastic chamber

Maintenance

• Inhalents anesthetics - Isoflurane - Sevoflurane

Inhalent drugs concentration

Isoflurane 3-5% Induction 1-2% Maintenance

sevoflurane 3-5% Induction3-4% Maintenance

Monitoring• Herat rate, respiratory rate,

temperature.• Different reflexes: righting reflex• Eosophageal stethoscope.• ECG leads should be placed near the

hearts.• Due to thick skin(scales), difficult to

use Pulse oximeter and invasive blood pressure monitoring.

• Small reptiles may be hypothermic, so external heat sources should be applied.

Fig.: Monitoring by using doppler flow

detector

Recovery • Takes hours to days with

injectable anesthetics but fast with inhalent anesthetics.

• Oxygen supply should be continue until animal is breathing regularly on its own.

• Supply fluid and heat according to needs.

• Provide analgesia

EmergenciesEmergency conditions Drug s Dose

Bradycardia Atropine 0.01-0.04 mg/kg SC, IM, IV,

Cardiac arrest: supply 100% oxygen

Epinephrine 0.1- 0.2 mg/kg IV, IO, IC, Intratracheally

Respiratory arrest (apnea)

Doxapram 5 mg/kg IM, IV; repeat every 10 min if required

Anesthesia in Rabbit• Preanesthetic consideration1. History and Physical exam - minimal handling to reduce

stress2. Laboratory evaluation - CBC, TP, Glucose, X-ray,

Ultrasound3. Fasting is not necessary 4. Stabilize fluid and electrolyte

Preanesthetic in Rabbits

drugs dose commentsacepromazine 0.25-1 mg/kg IM, SC,

IVMild to mod. Sedation, duration 4 hours.

Acepromazine+ butorphanol

0.5+ 0.5 mg/kg IM, SC

Mod. sedation

diazepam 1-2 mg/kg IM, SC, IV Mod, to deep sedation, duration 30-180 min

ketamine 25-50 mg/kg IM, IV Mod. To heavy sedation, duration 1 hour(IM), 15-20 min(IV)

Midazolam 0.5 -2 mg/kg IV, IM, IP

Mod, to deep sedation, duration < 2 hour

Xylazine 1-5 mg/kg IM, IV Mild to profound sedation, duration 30-60 min

Endotracheal tube intubation

Mostly 2.5 – 4 mm internal diameter tubes are used.

Intubating can be difficult in rabbits.

Intubation: with the help of Laryngoscope and blind intubation without laryngocope.

Oxygen flow 0.5 - 2 L/min. Fig.: ET tube intubation

Induction of Anesthesia• Either injectables or inhalants are used.

Anesthetics Dose (mg/kg)Ketamine + Diazepam 10+2; IVKetamine + Midazolam 25+1; IMKetamine + Xylazine 35+5; IM

50+5; IVMedetomidine+Fentanyl+Midazolam 0.2+0.02+1; IMMedetomidine+ketamine+Butorphanol

0.1+5+0.5; SC, IM

Propofol 3-6; IVInduction by inhalent anesthetics1. Isoflurane 2% to 3%2. Sevoflurane 3% to 5%

Maintenance and Monitoring

Maintenance1. Isoflurane 0.25% to 2%.2. Sevoflurane 2% to 3%.

MonitoringException: Palpebral reflex is normal with surgical plane of

anesthesia.. Surgical depth- pinnal reflex, pedal withdral reflex and

pedal pinch reflexes(faint forelimb reflex but no hindlimb reflex) and jaw tone .

Monitor respiration rate and depth. Central ear artery is a useful for peripheral pulse.

Recovery Keep the animal warm if temperature is subnormal. Monitor the animal’s hydration status.Analgesia

Anesthesia in ferrets• Similar to that of domestic cats

for endotracheal intubation, face mask and anesthesia.

• Do not have sweat glands so vulnerable to heat stress.

• Ferrets should be fasted for < 4 h prior to planned procedures

- to reduce the risk of vomiting or regurgitation and aspiration.•Fluid therapy by IV or SC or IO.

Premedication and analgesics drugs used in ferrets

drugs Doses(mg/kg)Atropine 0.02-0.05 SC, IM, IVGlycopyrrolate 0.01 IV, SC, IMAcepromazine 0.1-0.3 IM, IVXylazine 1-2 SC, IMKetamine 5-15 IMDiazepam 0.3-3.0 SC, IMButorphanol 0.4 IM; 4-6 hourlyflunixin 0.5-2.0 SC, 12-24 hourly

SC: subcutaneous, IM: intramuscular & IV: intravenous

Anesthetic induction drugs for Ferrets

drug Dose(mg/kg)Ketamine/acepromazine 25+0.25 IM

Ketamine/diazepam 5-25+0.5-2 IM

Ketamine/xylazine 25+1-2 IM

Ketamine/butorphanol 15+0.2 IM

Ketamine/butorphanol/ acepromazine 15+0.2+0.1 IM

Pentobarbital 25- 30 IV, 36 IP

Propofol 3-6 IV

For induction, both injectables anesthetics or inhalent anesthetics used.Common injectable anesthetics are given in the table below.

Induction and maintenance anesthesia

• Induction and Maintenance by inhalant gas anesthesia

Inhalent anesthetics

Concentration

Halothane 3-3.5% induction

0.5-2.5% maintenance

Isoflurane or Sevoflurane

5% induction

2-3% maintenance

Monitoring• Anesthetic depth monitoring using physiologic

reflexes such as palpebral, muscle tone, withdrawal reflex and gross purposeful movement.

• Monitoring of heart rate and rhythm: bell or esophageal stethoscope.

• Observation of patient and anesthetics bag and auscultation of lung fields for respiratory rate, rhythm and depth using bell stethoscope.

• Prone to hypothermia and hyperthermia, so temperature should be monitored also.

Recovery• Maintain heat and fluid support.• Supply oxygen till showing sign

of recovery.• Extubation only done after

swallowing reflex.

Emergency drugs used in Ferrets

Anesthesia in rodents• Rodents includes the pet species

Guinea pig, rats, mice, gerbils and hamsters.

History and Physical exam • Accurate weightLaboratory data• CBC, TP, Glucose, BUN, Creatinine,

ALT and AST. Fluid therapy• Fluids are usually administerd as

boluses. • Subcutaneous and intraperitoneal

routes are also used in emergency to maintain hydration status.

• Intubation: 12 to 18 G plastic intravenous catheters.

• Face mask: mostly used due to small tracheal size or narrow oropharynx.

• In guinea pigs, frequent aspiration of the secreted materials from nasal and oropharynx, so necessary to ensure a clear airway.

Sedative and premedication used in rodents

Drugs dosesAtropine 0.05-0.1 mg/kg

SCglycopyrollate 0.01-0.02 mg/kg

SCKetamine 20-40mg/kg IMMidazolam 1-2 mg/kg IMAcepromazine 0.5 – 2.5 mg/kg

IMXylazine 5-10 mg/kg IM, IP

Carprofen 5 mg/kg SCbutorphanol 0.1 mg/kg SC

Induction and Maintenance

Induction:• By both injectables and

inhalent anesthetics.• Injectable anesthetics 1. Propofol: 10 mg/kg IV 2. Ketamine + Midazolam :

5-15+ 0.1- 0.5 mg/kg IM• By inhalant anesthetics 1. Isoflurane 2% to 3% 2. Sevoflurane 3% to 5% Maintenance 1. Isoflurane 0.25% to 2% 2. Sevoflurane 2% to 3%

Monitoring • Anesthetic depth monitoring using physiologic reflexes such as

palpebral, pinnal reflex, muscle tone, withdrawal reflex and gross purposeful movement.

• Basic physiologic monitoring: heart rate, respiratory rate, and body temperature

• Because of the very high heart rates, the ECG is almost exclusively required to obtain correct heart rate.

• Noninvasive blood pressure monitoring is best achieved in rats and mice using Doppler flow detector and sphygmomanometer.

• Pulse oximetry and capnogrpahy.• Fluids need to be administered to avoid hypovolemia and

maintain stable hemodynamics .

Recovery• Maintain heat• Fluid support• O2 supply till recovery• Pain medication

Emergency drugs used in Rodents

Fish anesthesia• Indications - Any painful procedure like

trauma.- Sedation during shipping.- Diagnostic imaging.- Stripping milt (eggs).

Preanesthetic considerationA thorough pre-anesthetic physical examination,

cardiovascular system is not redially achievable.Use least amount of restraint possible. Use wet latex

gloves when handling the fish to minimize disruption to mucous membrane.

Withhold of food should be 12 to 24 hours to reduce - risk of regurgitation of food that may lodge in gills

and - degradation the water quality.

• Preanesthetic medicines are not commonly used.

• Ectotherm so maintain body temperature from external sources.

• Hypothermia prolongs recovery and decrease immune system.

Anesthetic agents in fish

Agent concentration comment

MS-222(tricaine methane sulfonate)

75-125mg/ml Induction dose( Sodium bicarbonate added to maintain pH).

50-75mg/ml Maintenance dose

Etomidate 2-4mg/L Minimal effective dose

7-20mg/L Maximum safe dose.

Clove oil (Eugenol) 40-100mg/L Effective dose

Isoflurane 0.40-0.75ml/L Induction dose

0.25-0.40ml/L Maintenance dose

Level of sufficient anesthesia reached when

Total loss of body equilibrium

Loss of muscle tone Decreased

respiratory rate No response to

external stimuli.

• Anesthetic Overdose:- Move fish to untreated, oxygenated water.- Increase gentle flow of water over the gills.- If spontaneous respirations do not occur within

2 minutes, assist respirations: 1. Move the fish gently through the water. 2. slowly pump oxygenated water into the fish’s mouth and across its gills.

References1. Handbook of Veterinary Anesthesia, 5th edition by William W.

Muir, III, John A.E. Hubbell, Richard Bednarski and Phillip Lerche.

2. The Merck Veterinary manual, 10th edition.3. Anesthesia for the Pet practitioner, 3rd edition by Karen

Faunt.4. Anesthesia of Exotic Pets by L.A. Longley.5. Essential of Avian Medicine and surgery, 3rd edition by Brian

H. Coles.6. Avian Medicine, 2nd edition by Jaine Samour.7. Compendium Journal.

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