Type of Animal	Blood Volume (mL/kg)
Chicken	60
Reptile	90.8
Frog	95
Fish	17-28
Mouse	50-60
Rat	60
Gerbil	78
Syrian hamster	78
Guinea pig	60-65
Chinchilla	65
Rabbit	55-65
Ferret	60

b. Contraindications to anesthesia

(1) A blood transfusion may be needed if packed cell volume is low

Perilously Low Packed Cell Volumes in Exotic Animals

Type of Animal	Packed Cell Volume (%)
Avian	<25
Reptile	<17 to 20
Amphibian	<20
Rodent/lagomorphs	<20
Mustelid	<25
Felid	<15
Swine	<20
Camelid	<20

(2) Fluids (3 to 5 mL/kg of body weight/hr) should be supplemented during surgery

Perilously High Packed Cell Volumes in Exotic Animals

Type of Animal	Packed Cell Volume (%)
Avian	>50 to 60
Reptile	>50 to 60
Amphibian	>60
Rodent/lagomorphs	>55 to 60
Mustelid	>60
Felid	>50
Swine	>50
Camelid	>50

(3) Amino acid or plasma supplementation may be needed if total protein is less than 3 g/dL; refractometers and colorimetric tests frequently used at diagnostic laboratories for mammalian blood often register falsely low proteins in nonmammalian species; the biuret method is the most accurate in avian species

(4) Administer 5% dextrose or delay anesthesia if the glucose is low

Perilously Low Blood Glucose Levels in Exotic Animals

Type of Animal	Glucose (mg/dL)
Avian	<150
Reptile	30-100
Amphibian	<50
Rodent/lagomorphs	<80-100
Mustelid	<70-100
Felid	<80
Swine	<60
Camelid	<60

(5) Correct low calcium to greater than 8 mg/dL

(6) Correct low potassium to greater than 3.5 mg/dL

3. Further evaluation

a. Oral/fecal Gram stains in nonmammalian species

b. Bacterial culture and sensitivity testing

c. Fecal/urinalysis

d. Complete hemogram/biochemical profile

e. Radiographs/ultrasound

f. Clotting profile

g. Electrocardiogram/echocardiography

II Preanesthetic fasting

A Hypoglycemia can occur within a few hours in very small mammals

Time for Preanesthetic Food Withdrawal in Exotic Animals

Type of Animal	Time (hr)
Birds <100 g	0
Large psittacine bird	1 to 2
Raptor, ratite, fowl, waterfowl	12 to 24
Carnivorous reptile ingesting whole prey	>5 days
Reptile <200 g	2 to 4
Reptile 200 to 500 g	12
Reptile >500 g	24+
Amphibian	24
Fish	24
Rodent <200 g	0-2
Rodent >200 g	>6
Guinea pig	6-8
Ferret	3-6
Rabbit	0-24
Felid	24
Swine	24
Camelid	24 to 48

III Maintaining homeothermy

A Hypothermia depresses the respiratory control system

1. Small animals are predisposed to hypothermia; they lose heat rapidly as a result of high surface-area-to-volume ratios

2. Ectotherms (reptiles, fish, and amphibians) do not generate their own heat; they require external heat sources to maintain their body temperature; hypothermia depresses the immune system and slows healing

3. Hypothermia can result in brain damage, shock, electrolyte imbalances, and disseminated intravascular coagulation

a. Well-insulated, small animals such as rabbits, chinchillas, water birds, and birds in winter plumage are susceptible to hyperthermia

b. Ungulates are prone to malignant hyperthermia; stress, high ambient temperature, and high relative humidity during immobilization increase the likelihood of hyperthermia

B Methods of monitoring core body temperature (skin temperature is not reliable)

1. Esophageal thermometer

2. Rectal/cloacal thermometer

C Heat sources and retaining heat

1. Always monitor heat sources to avoid iatrogenic burns and hyperthermia

a. Skin temperature

b. Surface temperature where the animal’s body is in contact with a warmed surface

c. Ambient temperature in incubators

2. Water-circulating heating pad

a. Very safe

b. High maintenance cost if punctured

3. Electric coil-type heating pads

a. Likely to cause iatrogenic burns

b. Inexpensive

c. Should never be set on high

4. Incubators

a. Must be preheated

b. Useful before and after anesthesia

c. Must be escape-proof

5. Hot water bottles

a. Watch for overheating especially if warmed in a microwave

b. Act as a heat sink after they cool

6. Forced warm air blankets

a. Very safe

b. Blankets warm immediate surroundings

c. Animal’s temperature must be monitored

7. Prevention of heat dissipation

a. Plastic bag or aluminum foil

b. Plastic bubble wrap

c. Minimize the amount of hair clipped

d. Use warm prep solutions and warm surgical flush

e. Quickly cover the exposed surface with a drape

f. Minimize the duration of anesthesia

IV Fluids

A Perioperative hypovolemia must be prevented to decrease postoperative morbidity and mortality

B Preheat to 80° F to 95° F (26° C to 35° C) for animals weighing less than 1 kg and for all ectotherms

1. Incubator

a. Stable, consistent temperatures must be maintained

b. Microbial growth may occur

2. Warm water bath

a. Stable, consistent temperatures must be maintained

b. Water must be kept warm

3. Microwave fluids

a. Frequently have hot spots

b. Should be well mixed

4. Placing intravenous (IV) tubing in warm water bath

a. Quick method to warm fluids in emergency

b. Effluent temperature must be carefully monitored

5. Fluid heating devices (Hotline, SIS Level 1, Inc.)

a. Warms IV fluids to above 104° F (40° C)

C Administration (route) (Table 26-1)

TABLE 26-1

Sites for Parenteral Access or Injection in Birds and Small Mammals

Species	Sites for Parenteral Access or Injection	Comment
Bird	IM, IO, IV: basilic, jugular, medial metatarsal
Rat and mouse	SQ, IM, IP, IO, IV: jugular, lateral tail	Lateral tail veins on mice are difficult to obtain blood from except by capillary action
Gerbil	SQ, IM, IP, IO, IV: lateral tail, saphenous, metatarsal	25-gauge needle
Hamster	SQ, IM, IP, IO (tibial crest), IV: lateral tarsus, cephalic, lingual, dorsal penile	IM: maximal volume 0.25 mL
		IO: use 22-gauge spinal needle
		IV: access is difficult, use 27- to 30-gauge needle
Chinchilla	SQ, IM, IP, IO, IV: femoral, cephalic, lateral saphenous, jugular, auricular, dorsal penile lateral abdomen, tail	IM: 23-gauge or smaller and maximum 0.3 mL
		IV: 25-gauge or smaller needle
Guinea pig	SQ, IM, IP, IO (trochanteric fossa), IV: marginal ear, medial saphenous, lateral saphenous, proximal to hock, dorsal penile, jugular	Self-mutilation can occur with IM injections; vascular access is usually difficult with short, mobile, friable veins
Rabbit	SQ, IM, IP, IO (trochanteric fossa), IV: marginal ear, cephalic, lateral saphenous, jugular	Blood clots quickly, external jugular is primary drainage for head (swelling occurs if catheter remains in place)
Ferret	SQ, IM, IP, IO, IV: cephalic, jugular, lateral saphenous, lateral tail

IM, Intramuscular; IO, intraosseous; IP, intraperitoneal; IV, intravenous; SQ, subcutaneous.

1. IV or intraosseous (IO) administration is best; the humerus in all birds and the femur in many birds are pneumatic bones; placing IO catheters in these bones causes iatrogenic drowning

2. Subcutaneous (SQ) fluids (usually 5% to 10% of body weight) are given before induction of anesthesia to allow absorption and volume expansion

3. Intraperitoneal fluids

a. More rapidly absorbed than SQ fluids

b. Could cause peritonitis

c. Must be warmed to body temperature

d. Not in birds

e. Not in pregnant animals

f. Bladder should be expressed before administration

4. Colonic fluids

a. Isotonic, warmed solution may be given as an enema

b. Fluids are often absorbed more rapidly across the mucosa of the colon than from the SQ space

D Fluid rates

1. Standard maintenance: 40 to 100 mL/kg of body weight/ 24 hr; the higher end of the range is used for neonates, birds, and animals with high metabolic rates

2. Intraoperative: 3 to 5 mL/kg/hr

3. Shock: 5 mL/kg in 20 minutes and reevaluate

E Fluid rate control

1. Rates less than 10 mL/hr require an IV fluid infusion pump to ensure accuracy

2. Rates of 10 to 50 mL/hr are accurately measured with inline flow controls or burette fluid chambers

3. Rates greater than 50 mL/hr are accurately measured off of most fluid containers

F Fluid choice (see Chapter 16)

G Blood transfusion (see Chapter 16)

1. Ethylenediamine tetra-acetic acid (EDTA) should not be used in small exotic animals to avoid hypocalcemia

2. Heparin is the anticoagulant of choice for birds

3. Birds can receive one interspecies or genera transfusion if a donor of the same species is not available, but survival of red blood cells over 24 hours is limited; intraspecific or at least intragenera transfusions are preferred

a. Pigeons are the most common donors

b. Transfusions should not be repeated for at least 3 weeks

H Blood substitutes

1. Oxyglobin (Biopure Corp.) can be used in most species as a blood substitute (10 to 30 mL/kg)

V Premedication

A If necessary, administer antibiotics to achieve adequate serum levels before induction of anesthesia

B Select appropriate preanesthetic medication

C Birds (Table 26-2)

TABLE 26-2

Injectable Sedative and Analgesic Drugs for Avian Use

Drug	Dose
Atropine	0.01-0.02 mg/kg IV, 0.02-0.08 IM
Glycopyrrolate	0.01-0.02 mg/kg IV, IM
Alphaxalone	10-14 mg/kg IV
Buprenorphine	0.01-0.10 mg/kg IM
Butorphanol	0.1-4.0 mg/kg IM
Codeine	30 mg/kg IM
Fentanyl	0.2 mg/kg IM
Morphine	0.1-3.0 mg/kg IV, 2.5-30 mg/kg IM, SQ
Diazepam	0.05-0.15 mg/kgIV, 0.2-0.5 mg/kg IM
Midazolam	0.05-0.15 mg/kg IV, 0.1-0.5 mg/kg IM
	7.0 mg/kg intranasally
Detomidine	12 mg/kg intranasally
Ketamine >1 kg	15-20 mg/kg IM
<1 kg	30-40 mg/kg IM
Ketamine/midazolam	20-40 mg/kg IM+
	4 mg/kg IM
Ketamine/xylazine	10-30 mg/kg IM+
	2-6 mg/kg IM
Ketamine/midazolam/xylazine	40-50 mg/kg + 3.65 mg/kg +
	10 mg/kg intranasally
Propofol	10 mg/kg slow IV infusion until effective
	Up to 3 mg/kg increments for supplemental doses
Etomidate	10-20 mg/kg IM
Betamethasone	0.1 mg/kg IM
Dexamethasone	2-4 mg/kg IV, IM
Methylprednisolone	0.5-1.0 mg/kg (route?)
Prednisolone sodium succinate	0.5-1.0 mg/kg IV, IM
Ketoprofen	5-10 mg/kg IM, 2 SQ
Flunixin meglumine	1-10 mg/kg IV, IM
Phenylbutazone	3.5-7.0 mg/kg IV
Carprofen	2-10 mg/kg IM, 1 SQ

IM, Intramuscular; IV, intravenous; SQ, subcutaneous.

1. Anticholinergics are not indicated because they make respiratory secretions more viscous

2. Preanesthetics are rarely indicated if the bird is small enough to be manually restrained

a. They may delay recovery

b. They may depress respirations

c. Diazepam/midazolam is the most efficacious and safe—0.05 to 0.15 mg/kg IV, 0.2 to 0.5 mg/kg intramuscularly (IM), 7.3 mg/kg intranasally

(1) Can be reversed with flumazenil 0.13 mg/kg

d. Detomidine 12 mg/kg intranasally

e. Combination of midazolam (3.6 mg/kg), xylazine (10 mg/kg), and ketamine (40 to 50 mg/kg) intranasally

3. Because their long legs are susceptible to trauma, ratites, storks, and long-legged wading birds weighing more than 15 kg may benefit from sedation before capture and/or restraint

a. Xylazine 0.2 to 0.4 mg/kg IM

b. Tiletamine-zolazepam (Telazol) 2 to 5 mg/kg IM

D Reptiles

1. Anticholinergics make respiratory secretions more viscous

2. Preanesthetics are rarely indicated, except in large, aggressive, and/or venomous reptiles

E Amphibians: preanesthetics are not routinely used

F Fish: preanesthetics are not routinely used

G Rodents, guinea pigs, and rabbits

1. Atropine or glycopyrrolate is useful for decreasing airway secretions and maintaining heart rate

2. Some rabbits have atropinase—use glycopyrrolate instead (see Chapter 3)

3. Acepromazine and diazepam are effective preanesthetics

4. Acepromazine is not recommended in gerbils, because it may potentiate seizures

5. Hamsters require up to 5 mg/kg of acepromazine

6. Combination of fentanyl and fluanisone (Hypnorm) produces sedation and immobilization for about 30 to 60 minutes; analgesic effects may persist

H Mustelids (ferrets)

1. Anticholinergics are given as needed to maintain heart rate and decrease secretions

2. Diazepam or midazolam provides light tranquilization but no analgesia

3. Acepromazine provides light to moderate tranquilization but also no analgesia; should be avoided in hypovolemic or very sick animals

4. Xylazine or dexmedetomidine produces dose-dependent sedation, immobilization, and analgesia

5. Opioids potentiate sedation and provide analgesia; usually given in combination with other sedatives or tranquilizers

6. Ketamine produces dose-dependent sedation; muscle relaxation is poor if it is given alone

I Felids

1. Preanesthetics are not routinely used

2. Anticholinergics can be used at standard domestic cat doses

a. Atropine 0.02 to 0.04 mg/kg SQ, IM, IV

b. Glycopyrrolate 0.005 to 0.010 mg/kg SQ, IM, IV

J Pigs (see Chapter 24)

K Camelids (See Chapter 25)

VI Monitoring anesthesia

A Generalities

1. Pulse rate and character: a decrease in heart rate to less than 80% of the stabilized rate after induction indicates that anesthesia should be lightened

2. Respiratory rate, volume, and character (e.g., apneustic)

a. A decreasing respiratory rate or apneustic/erratic patterns indicate that anesthesia should be lightened

b. Ectotherms and birds normally develop apnea at surgical planes of anesthesia; plan to administer positive-pressure ventilation at least two to six times per minute

3. Body temperature

a. Body temperature can drop as much as 10° C in 15 to 20 minutes

4. The level of anesthesia

a. Reflexes are a good index of anesthetic depth; the signs vary between the species

(1) Auricular reflex is useful in rabbits

B Equipment

1. Electrocardiogram modifications

a. To protect delicate skin or to penetrate thick skin, attach clips to steel sutures or metal hub needles placed through the skin

b. Attach clips to alcohol-soaked pads placed at the usual lead sites

c. Wings are used for forelimb lead sites in birds

d. Place one clip cranial and one caudal to the heart in legless animals

2. Doppler placement

a. Over the heart in small animals

b. Over a peripheral artery

(1) Birds: medial metatarsal, brachial

(2) Reptiles: tail artery

(3) Rodents/lagomorph: ear, femoral, saphenous, foot pad (do not shave feet)

(4) Mustelids: tail, foot pad, saphenous

3. Pulse oximeter

a. Measures the percentage hemoglobin saturation with oxygen in addition to heart rate

b. Placement: tongue, esophageal

(1) Measures across any nonpigmented capillary bed

(2) Mucous membranes are excellent sampling sites: oral or nasal mucosa, cloaca, or vulva

(3) Measures through nonpigmented skin: ear, wing web, thin skin of flank or abdomen

4. Heart rate monitors must be suited for high heart rates and be able to read up to 350 beats/min in rabbits and more than 600 beats/min in mice

5. Respiratory monitors must be sensitive enough to detect small tidal volumes

Avian Anesthesia (less than 15 kg)

I Attaining surgical anesthesia

A Toe, tail, and cloacal pinches

B Most birds have a slow third-eyelid response; the loss of this response in birds indicates that anesthesia should be decreased

C Response is not present in response to pinpricks to the cere

D Respirations are slow, deep, and regular

II Anesthetic procedure recommendations (Tables 26-2 and 26-3)

TABLE 26-3

Avian Anesthesia

Species	Drug	Intramuscular doses (mg/kg)
Birds >250 g	Ketamine	20-40
	Diazepam	1-1.5
Birds <250 g	Ketamine	30
Parakeet	Ketamine	30
	Xylazine	6.5
Cockatiel	Ketamine	25
	Xylazine	2.5
Amazon	Ketamine	10-20
	Xylazine	1-2
African Grey	Ketamine	15-20
	Xylazine	1.5
Cockatoo	Ketamine	20-30
	Xylazine	2.5-3.5
Macaw	Ketamine	15
	Xylazine	1.5-2
Hawk, Falcon	Ketamine	25-30
	Xylazine	2
Owl	Ketamine	10-15
	Xylazine	2
Great Horned Owl	Propofol	4.5 (induction)
		0.48 mg/kg/min (maintenance)