Special Species Dr. Bennett

Question 1

What are considered special species?

Considerations

Answer 1

Small mammals

incr pub awareness they are capable of experiencing pain & distress

specific challenges due to:

unfamiliar species

unfamiliar drugs

research requirements & legislation

ethical aspects of research projects

Question 2

What may be some causes for anesthetic deaths in rabbits compared to dogs & cats

Answer 2

maybe relate to CV & resp problems

? due to large surface area:volume ration

high metabolic rate & high rish of hypoglycemia

difficult to intubate due to small size & problems of maintaining patent airway

Question 3

Pre anesthetic assesment of small mammals

Answer 3

rats, mice & hamsters are nocturnal

rabbita are activea at dawn & dust (crepuscular)

Question 4

pre anesthetic management of small mammals

Answer 4

No fasting due to:

Rats & mice do not vomit, prone to hypoglycemia & dehydration

Rabbits & GP experience GI disturbances leading to changes in gut flora, ileus & enterotoxemia

All spp exhibit neophobia (fear of new things) - feed usual diet

plus high-energy & high water content

all are coprophagic- avoi use of E collar

Question 5

Complications seen in anesthesia of sm mammals

Answer 5

high risk of hypothermia

Question 6

How to administer drugs to small mammals

Answer 6

SQ preferred into scruff or flank

IP may be unreliable

IM (avoid if volume large)

use drugs w/ wide safety margin

ideally are reversible

e.g. Alfaxalone

Question 7

IV access in sm mammal spp

Answer 7

Rats: lateral tail v., make sure they are warm

Rabbits: auricular, cephalic & saphenous v.

GP & ferrets: cephalic v. (potentially saphenous v. also)

Use EMLA cream prior

Question 8

What is most commonly used injectable in lab rodents

Answer 8

Ketamine

used in combo with Alpha2 agonist

Question 9

Inhalant anesthetics in sm mammals

Answer 9

Isoflurane & sevoflurane

adverse effects well documented

can be used in all common lab rodents

isoflurane undergoes virtually no biotransformation

Question 10

Considerations of inhalant anes drugs w/ sm mammals

Answer 10

Mask induction may be associated w/ breath holding esp in Rabbits

some aversion to inhalants due to smell in rats & mice

less with Sevo & halothane than Iso

Iso particularly irritating to GP

Question 11

Airway management & intubation of sm mammals

Answer 11

placing ET tube narrows the airway & increases resistance to exhalation & potentiall the work of breathing

Question 12

Rabbit intubation

Answer 12

specific laryngoscope available for rabbits

Question 13

Types of breathing systems used in sm mammals

Answer 13

T-piece & Bain:

non-rebreathing

low resistance

need ot minimize dead space in order to prevent rebreathing

TV: 5-10 mL/kg small rodents

Question 14

Maintenance of body temp in sm mammals

Answer 14

electric & warm water blankets available

forced hot air blankets not practical in rats & mice

recover in an incubator

Question 15

Postoperative care & pain assessment in sm mammals

Answer 15

Can have changes in facial expression!

Question 16

Opioids in small mammals

Answer 16

Buprenophine used most commonly

35 x as potent as morphine in rats IM

long duration of action: 3-5 h mice, 6-8 h rats

less incidence of respiratory depression

May cause pica esp in rats

analogous to vomiting in other spp

if occurs switch to non opioid analgesic

Question 17

NSAIDs in sm. mammals

Answer 17

all drugs licensed fro use in animals can be administered in lab animals

oral meloxicam is highly palatable

duration of action not clear

8-24 hours

Question 18

Local anes in sm mammals

Answer 18

may be suitable for some procedures in combo with GA

dont exceed:

Lidocaine 10 mg/kg

bupivicaine 2 mg/kg

Question 19

Gabapentin & pregabalin in sm mammals

Answer 19

MAC sparing effects of gabapentin in rats using both iso & sevo

Question 20

Specifice Ferret anesthesia

Answer 20

sedation: medetomidine & butorphanol, reversal with atipamezole

Question 21

What are most commonly encountered reptiles for anesthesia

Answer 21

Crocodilians (alligators & crocs)

Chelonians (tortoises & turtles)

Squamates (snakes & lizards)

Question 22

Species specific considerations for reptiles

Answer 22

Metabolism & thermoregulation

CV system

Pulmonary system

Renal system

Hepatic system

some spp terrestrial & others aquatic!

Question 23

Reptile metabolism & thermoregulation

Answer 23

Poikilothermic/ectothermic

lower rates of metabolism compared to mammals

oxygen consumption varies from almost zero to that of a restin mammal (spp dependent)

Perferred optimal temperature zone (POTZ)

ensures optimal metabolic function

approx 20-25° C for aquatic & temperate spp

25-35° C for tropical spp

Question 24

reptile CV physiology

Answer 24

Squamates & chelonians

3 chambered heart - 2 atria 1 ventricle

Crocodilians

4 chambered heart somewhat similar to mammals

blood can be shunted from R-L & L-R

can lead to awakening during anesthesia

may affect patient monitorin e.g. blood gas analysis & SpO2

BP varies by spp & environment

values vary between 15-30 mmHg in chelonians, 60-80 mmHg in lizards

Question 25

reptile pulmonary system

Answer 25

**Chelonians & lizards:** **paired lungs** **chelonians obligate nasal breathers** **Snakes** **single functional R lung** **many also possess a R tracheal lung** functional units are ***ediculi & faveoli** analogus to alveoli* **anesthetic drugs may have more respiratory depressant effects compared w/ mammals (lack of diaphragm)** **Chelonians: dorsal survace of lung is attached to carapace, ventra surface to abdominal viscera***, no ribcage, mm used in locomotion are also involved in ventilation* high FiO2 may depress ventilation **recovery may be faster breathing room air (green iguana)**

Question 26

renal system of reptiles

Answer 26

**blood from hind limbs & tail may pass via the kidney before returning to heart** **little apparent effect on drug PK in healthy animals** **preferable to avoid nephrotoxic drugs inj into hindlimbs**

Question 27

hepatic system of reptiles

Answer 27

similar in structure & function to mammals ## Footnote **metabolic capacity lower than mammals** **thought to be responsible for prolonged recoveries seen after anesthesia**

Question 28

Pt assessment of reptiles

Answer 28

obtain bodyweight & assess gen. appearance Maintain POTZ

Question 29

Drug admin in reptiles

Answer 29

Snakes: **IM epaxial muscles** lizards: **IM triceps, biceps, quadriceps, semi-mem & semi-tend & tail** **Don't use tail in gecko!** Snakes and lizards **ventral coccygeal vein palatine vein** Tortoise and turtles **dorsal coccygeal vein** IV catheterization **coccygeal and abdominal veins jugular vein in tortoises** Venous sinuses **using stylet of an IV catheter**

Question 30

Sedatives used in reptiles

Answer 30

Benzodiazepines and alpha2-adrenoceptor agonists in combination injectable anesthetic drugs usually IM. E.g. **Medetomidine** ◦E.g. **Midazolam** **both can be reversed**

Question 31

injectable anesthetics

Answer 31

Propofol drug of choice if IV access is available **give slowly to avoid respiratory depression CRIs have been used in Green iguanas** Alfaxalone **minimal effect on HR & ventilation** Ketamine **effects (spp/dose) dependent** **recovery may be prolonged**

Question 32

intubation in reptile

Answer 32

In chelonians and crocodilians t**racheal rings are complete –avoid cuffed ET tubes** In chelonians **trachea bifurcates quite rostrallyso it is easy to intubate a bronchus**

Question 33

Maintenance of anesthesia in reptiles

Answer 33

Iso or sevo Options IM sedation –large and aggressive animals **ketamine +/-medetomidine or midazolam tiletamine+zolazepam** IV induction of anesthesia **propofol alfaxalone** Mask or chamber induction

Question 34

Fluid therapy of reptiles

Answer 34

some debate since blood is hypotonic compared to birds and mammals **use isotonic saline diluted (9:1 with sterile water) “reptile ringers” -\> 2 parts 2.5% dextrose/0.45% saline and 1 part LRS** may use lactated of acetated fluids some query about ability to metabolize lactate hypertonic crystalloids and colloids may be used in hypovolaemic animals **start at 1-2 mL/kg and re-assess**

Question 35

anes monitoring in reptiles

Answer 35

ECG **differences from mammals in configuration** ETCO2 **not reliable due to intra-pulmonary shunting of blood** pulse oximetry **not validated for reptilian species** ◦protect the eyes

Question 36

pain assessment & mgmt in reptiles

Answer 36

Opioids **species differences in response** **some information about morphine, tramadol, buprenorphine, butorphanol and hydromorphone** NSAIDs **evidence supports the efficacy of these drugs** Meloxicam **high bioavailability PO dose 0.2 mg/kg IV or PO** Local anesthetics **lidocaine**