Title: Anaesthesia of laboratory animals
1Anaesthesia of laboratory animals
- Timo Nevalainen
- Universities of Kuopio
- Finland
2A more pharmacologic presentation www.uku.fi/tne
valai/Anesthesia.ppt
3Terminology
- Anaesthesia without sensation
- an without, aestos sensation
- Analgesia without pain
- an without, algios pain
- Euthanasia good death
- eu good, thanatos death
4How anaesthesia is chosen ?
- Tradition
- look articles of your discipline
- Ask colleagues
- end up to tradition
- Rational way ?
5Anaesthesia, how ?
- Choice of anaesthetic
- minimal interference of study
- immobilisation and no/less pain
- nature of the procedure
- duration of the procedure
- Humane handling of animals and safety of
personnel are important
6Problems with laboratory animals
- Group anaesthesia
- Large species, strain etc. differences
- Follow-up difficulties
- Anaesthesia poorly known
- Clinical and research anaesthesia are not used
properly - Postoperative care does not work
7Pros and cons of anaesthesia
- Pros
- no pain
- no muscle reflexes
- no muscle tension
- Clinical anaesthesia
- Cons
- changes in the body
- physiological status different
- responses may be different
- Research anaesthesia
8Anaesthesia vs. CNS-mediated reflexes
- alphachloralose
- thiobarbiturate N2O
- cyclopropane
- barbiturates
- ether
- halothane
- chloroform
- Depresses least
- depresses most
9Inspection before anaesthesia
- Check animals before starting
- Do not anaesthetise sick animals, they are
unsuitable for experiments anyway - Pay attention to symptoms of infections
10Bedding Volatile Compounds / With Highest Sums
concentration microg/g
Vesel et al. 1966 Bedding volatile compounds
induce liver microsomal enzymes
11How to fast before anaesthesia ?
- Take away food - not water
- the smaller species, the faster metabolism, the
shorter fasting - no fasting for mouse
- abdominal procedures in rat, fast for 6 h
- guinea-pig 6 h
- rabbit 6 h
12Dangers of vomiting
- Horse vomits rupture of stomach
- ruminants can drop ruminating balls
- carnivores vomit easily
- among rodents guinea-pig vomits easily
- can drain into trachea and cause aspiration
pneumonia
13Handling vomiting dangers
- Fasting decreases amount vomited, but reflex
stays - if vomits, place head over table edge, drains
away from mouth - once anaesthetised, intubate, closes passage to
respiratory system
14Pre-anaesthetic hydration
- Give animal balanced electrolyte fluid to drink
couple of days before - yields better water balance
- continue a few days after anaesthesia (and
procedure)
15Pre-medication atropine
- No saliva, no vagal reflexes, less gut motility
- Dose rodents 0.05 mg/kg, rabbit 1-3 mg/kg about
30 min before - if autonomic nervous system is involved, atropine
may be contraindicated
16Sedative pre-medication
- Decrease dose of anaesthetic by 20-50
- better handling may be needed eg for iv injection
- if procedure is not painful, but immobilisation
is needed - some compounds dilate vessels - easier to see them
17Ensuring oxygenation
- Respiratory passages open
- posture, atropine
- additional oxygen
- tubing directly into mouth
- less dead space
- intubation
18Pulse oxymeter
19Sensor around leg
20Maintaining normal temp
21ECG-recording
22Control of anaesthesia
- Inhalation is well controlled
- iv-bolus anaesthesia - you give half of
calculated dose, the rest to effect - infusion anaesthesia also well controlled
- im, ip ja sc administration you give calculated
bolus - response may be variable
23Inhalation - open mask
24Intubation
- Mouse - tracheostomy
- rat - tube outer diameter 1-1.5 mm, length 2 cm
attached snugly inside wider tube - rat placed on back, fixed by maxilla incisors,
tongue pulled out - larynx visible, becomes easier with high
intensity light directed to neck
25Intubation
- Guinea pig intubation - easier version of rat,
tube outer diameter 2 - 2.5 mm - Rabbit intubation difficult
- laryngospasm unless not deep enough
- small place, otoscope / pediatric laryngoscope
- tube outer diameter 3 - 3.5 mm, no cuff
- Rabbit guided or blind intubation
26Mouse intubation video
27Using otoscope
28Air movement ?
29Rodent respirator
30Wet - loosing heat
31Skin disinfection
32Assessment of anaesthetic depth (video)
- Mouse
- respiratory rate, cornea
- tail pinch and pedal reflex
- pedal best
- Rat
- respiratory rate, tail pinch
- pedal reflex and ear pinch
- ear pinch best
33Tail pinch
34Pedal reflex
35Anaesthetic depth
- Guinea-pig
- palpebral reflex and ear pinch
- ear pinch best
- may move 1-2 times, is not lightening of
anaesthesia - Rabbit
- light surgical - pedal reflex
- medium depth - palpebral reflex ear pinch
- corneal reflex - dangerously deep
36Ear pinch
37Dose memos
- www.uku.fi/tnevalai/ratmouseanes.html
-
- Rabbit dose calculator
- www.morfz.com/rx/drugcalc.html
38Hypnorm midazolam
- clinical anaesthesia, reasonable safety margin
- NOT to be given ip, liver metabolism weakens
effect - contains fentanyl controlled substance
- recovery is speeded by nalorphin
- Rat Combination 0.15 - 0.2 ml / 100 g sc
- Mouse Combination 0.10 - 0.15 ml / 20 g sc
39Hypnorm Midazolam
- Combination
- One part HypnormR (fentanyl-fluanisone) one
part midazolam (DormicumR, 5 mg/ml) two parts
sterile water - Mix both drugs first with water and then
combine. Do not keep in refrigerator. - Duration of anesthesia Mouse 30-60 min, rat
20-90 min - Reversal Nalorphine 1 mg / kg iv, im, ip
40Medetomidine fentanyl
- Works reasonably well in rats
- animals pale and urine drips
- major advantage antagonist wakes them real
fast
41Chloralhydrate
- Common in neuropharmacology
- if too concentrated, fatal paralytic ileus,
abdomen dilated, do badly and die - correct concentration is 36 mg/ml or less
42Permanent iv-access
43Infusion anaesthesia
- Typical compound propofol
- used in rats, single bolus 10 mg/kg produces
anaesthesia of about 5 min - infusion anaesthesia can provide stable
anaesthetic level without a vaporizer
44Barbiturate anaesthesia
- Safety margin in rabbits narrow
- may lead to 20-40 mortality
- if used - only for terminal procedures
- Mouse - the same situation
- can combine with e.g. ethanol
- there are better combinations
45Complete inhalation set
46Induction chamber
47Nose cones with exhaust
48THE UNIVENTOR 400 ANAESTHESIA UNIT
designed to control the mixture of anesthetic and
air with the precision required to successfully
operate on animals weighing from 20-500 grams
www.agnthos.se
49Inhalation
- halothane
- common inhalation compound
- does not evaporate concentrations with mortality
at room temperature - liver necrosis
- cheapest of proper inhalation compounds
- good clinical anaesthesia with guidance
50Isoflurane
- Combines reasonable research anaesthesia and good
guidance - more expensive than halothane
- requires own vaporizer
- no mortal concentrations at room temperature
51No ether, neither chloroform
- Evaporate to mortal concentrations at room
temperature - ether explodes, and carcasses in cooler of
freezer smell a long time - chloroform is liver toxic and suspected carcinogen
52CO2
- Useful for 1-2 min procedures, no longer
- for rats and mice
- incubation box with animals, tube CO2 in at a
rate 0.6 x box volume l/min - righting reflex disappears, move to mouth cone
with 50 CO2 and 50 O2
53Postoperative care
- temperature
- infrared light bulb
- insulation
- fluid
- ip or sc as boluses
- air humidification
- additional oxygen
- carbogen flow to chamber
54Insulated, recovering rat
55Recovery chamber
56Eyes stay open and.dry
57Strategy for research anaesthesia
- Simple is best - avoid polypharmacy
- Effect on your study
- Prefer inhalation
- stable anaesthesia
- can measure inhalant concentration from expired
air best description of anaesthesia
58Pain?
- Unpleasant sensory or emotional feeling, may /
may not be associated with real or potential
damage - It is reasonable to assume that animals feel pain
- The mechanisms behind are similar
59Animal pain
- may not be identical to humans
- it is assumed that intensity and duration of pain
is variable in specific tissue damage between
species - fast recovery leads to underestimation of pain
and failure to give analgesic
60Why pain?
- It is a warning signal
- specific part of body will not be used
- Pain can also be harmful
- lack of use spasms -gt weakness, loss of muscle
and permanent change - Pain can result in lack of appetite and drinking
61Pain assessment
- difficult in humans even though we understand
what they say - animal approaches
- anthropomorphic way
- based on clinical findings
- activity, grooming, immobility, vocalization,
posture, aggressiveness
62Pain assessment
- rodents are nocturnal
- animals should not notice
- infrared lamp during dark
- handling responses
- www.lal.org.uk/pdffiles/fleck.pdf
63Signs of pain
- Species and procedure specific
- Scoring system is a necessity
- analgesic treatment
- verification of analgesia efficacy
- postoperative analgesia the most common form
- humans with neoplasia and infections receive
analgesia - fear for interference in animal studies
64Difficulty of assessment
- Animal shows no sign of pain
- pain will not be treated
- Comparison to human situation
- better to give a single dose
- repeated dose may be problematic
- e.g. appetite may be lost -gt recovery delayed
65Pain scoring requires
- knowledge of
- species specific behavior
- behavior before the procedure
- palpation of the tissue response
- evaluation of sore area (e.g. leg)
- knowledge on efficient analgesics doses, and
possible behavioral consequences
66Pain assessment after laparatomy in rats
- Stage 1 Visual Analogue Score (VAS)
- assess pain experienced by the rat with a mark on
a 10 cm line - there are 4 clips to assess
67Continues..
- Stage 2 Instructions
- become familiar with behaviors typical to pain
- do not count at this point
- Only three behaviors needs to be recognized
- order haphazard like in real life
68Pain behaviors 1
- Twitches
- usually when the rat rests
- most common on back, fur coat movement
- also on the head
- most common behavior
- Back arching
- feet extended, belly goes up, arching back
- often just prior to walking
69Pain behaviors..
- Falling
- temporary loss of balance
- falls to side or backwards
- Each of all three are counted as one
70Ideal analgesic
- Does not interfere the study
- No sedation
- Long duration
- Efficient analgesia
71Analgesia contraindications
- Analgesia does NOT replace
- good surgical technique
- good peri- and postoperative care
- Analgesia should not interfere with the study or
interpretation of the results
72Methods
- systemic analgesia
- duration?
- local analgesia
- applied on the incision area
73Analgesics
- Rat (R) and Mouse (M)
- Opioids - look for duration
- Buprenorphine
- 0.05(R), 0.1(M) mg/kg sc / 6-12 h
- Butorphanol 2.0(R) mg /kg sc / 1-2 h
- Petidine 10-20(RM) mg/kg sc or im / 3 h
- Morphine 2-5(RM) mg/kg sc /4 h
74Other
- Rat (R) and Mouse (M) doses
- many given per os / dissolve in water
- Carpofen 5(RM) mg/kg sc or per os
- R 12-24h
- Fluniksine 2.0(R) mg/kg sc /1-2h
- Ketoprofeine (R) 5 mg/kg im/12-24h
75Per os administration
76Analgesia - advantages
- Faster recovery
- Faster return of appetite
- No weight loss
- Which is better
- effect of pain and procedure or only effect
of procedure - Ethically right
77How to use ?
- Small surgical procedures -gt single injection
e.g. buprenorphine - in major interventions continue 2-3 days
- Additionally place local analgesia into the
incision - Follow animals and verify efficacy
78Books
- P.Flecknell. Laboratory Animal Anaesthesia.
Academic Press, 1996 - H.B. Waynforth P.A. Flecknell Experimental and
Surgical Technique in the Rat. Academic Press
1992 - D.H. Kohn, S.K. Wixson, W.J. White, G.J. Benson.
Anesthesia and Analgesia in Laboratory Animals.
Academic Press 1997.