Anaesthesia For Minor Procedures Flashcards
Why do we use anaesthesia?
Immobility, prevent pain, prevent distress
Why is anesthesia important?
High quality data, lower variation in no. of animals needed, lower mortality, refine, reduce
Fasting in anaesthesia?
Anaesthesia = no protective coughing reflex = inhale vomit = pneumonia (dogs, cats, primates, ferrets, pigs, sheep, ruminants).
Rodents, rabbits, guinea pigs = no vomit
Acclimatization in anesthesia?
- 7-10 days in animal unit
- Reduce stress = safer
- Check animal health and weight
Local anaesthetic in anaesthesia?
Anaesthetize large areas by blocking nerve trunks = topical for larger species BUT need restrain/training to accept
Pros and cons of inhalants?
Pros: easy administration, smooth and rapid induction, change depth, rapid recovery
Cons: expensive equipment, anaesthetise 1 at a time, waste gas must be removed
Pros and cons of injectables?
Pros: multiple at once, no specialist equipment, just O2
Cons: can’t change dose, variability in response
What are signs of poor health in animals?
- Ruffled coat
- Sunken/closed eyes
- Hunched posture
- Pale ears/tail
- Not active
- Discharge around eye
How does anaesthesia affect your results?
- Cardiovascular + respiratory depression, hypothermia
- Alter immune, tumour metastatic rate, organ blood flow, compete for enzyme pathways, interact w/ receptors, GI motility
=> REVIEW LITERATURE
What are the common injectable agents
Ketamine (+ Medetomidine)
- 30 mins surgical anaesthesia, ~180 mins recovery
- Atipamezole partially reverses
- Provide O2
- Give extra analgesia after reversal
Hypnorm (+ midazolam/diazepam)
- Surgical anaesthesia
- Buprenophine partially reverses
Propofol
- Surgical anaesthsia 5-10 mins via IV
Alphaxalone
What are uncommon injectable anaesthetics?
Etomidate (+fentanyl)
Pentobarbital (light anaesthsia, narrow safety margin, 7hr recovery)
Compare the different routes of adminstration of injectables?
IM: 5-10 mins to develop. Pain on administration in small. Some = irritant = muscle damage E.g. Ketamine.
SC: 5-15. Less stress, more consistent than IM/IP. Not all agents suitable. Slower absorption (10 mins), easy, well tolerated
IP: Widely used. 5-10% times not all anaesthetic administered. Not all suitable. Less pain, easier but also problems w/ airsac in birds
IV: Rapid effect = dose adjustable. Better for large. Check dose appropriate on 1/2 animals
How do you assess anaesthesia depth?
Withdrawal Reflexes:
- tail pinch (light-med)/pedal withdrawal (med-deep)
Eye Position:
- useful in dog, cat, pig, sheep = eye gradually rotates down w/ anaesthesia, blink reflex lost, deep = eye rotates back up and fixed centrally
- Rodents = fixed eye position, blink may remain
- Rabbits = variation, deep = rotate and protrude
Ear Pinch:
- Lost in rabbits and guinea pigs
What do we need to support and monitor during anaesthesia?
- Support respiratory function
- Prevent eye injury
- Prevent hypothermia
- Monitor HR
How can you assess respiration?
- Observe pattern and depth of chest movements
- Electronic monitor
- Reduction of 50% rate = concerning
- Lay so airway unobstructed, head and neck extended
How do you prevent eye injury?
Ophthalmic ointment/taping lids = >15 mins anaesthsia
What are the steps of administering injectables?
- Place into clean cage while anaesthetic takes effect
- Check leg withdrawal reflex
- If stop breathing = administer O2, extend head and gently squeeze chest, give antagonist, give respiratory stimulant E.g. dopzapram, use syringe to inflate lungs
How does surgery affect body temperature?
Anaesthetics + cold fluids + shaving + cold anaesthetic gases = hypothermia
Hypothermia = fall in body temp >2 degrees = cardia arrest, altered cell membrane transport systems, enzyme activity
How do you maintain temperature during injectables?
- Heating pad
- Monitor temp
- Avoid excessive skin disinfectants
- Minimize shaving
- Avoid unnecessary exposure of abdominal viscera
- Warm fluids to body temp before administration
- Use forced-air warming blankets in big species
- Insulate w/ bubble wrap
What are the most common inhalational agents?
Isoflurane - rapid induction and recovery, depth easily and rapidly altered. Pungent but no breath holding in species except rabbit and guinea pig. Almost no biotransformation and nearly completely eliminated in exhaled air
Sevoflurane - more rapid induction/recovery than isoflurane, alter depth, non-explosive/flammable. Less pungent than others, mask well tolerated in most except rabbits and guinea pigs. Many recover w/o involuntary excitement
Desflurane - used, expensive, most rapid onset/recovery, relatively non-irritant. Least degree of metabolism. Needs pressurized, temperature-controlled vaporiser due to low boiling point. Not widely used in vets/lab.
Halothane - no longer available commercially in many countries
Methoxyflurane - similar to halothane
Ether - not used in EU/US = unpleasant to inhale and safety risk (explosive w/ air/oxygen)
What are the recovery times in rats after 1hr of anaesthesia
Desflurane - 5 mins = righting reflex, 10 mins = rotarod test
Sevoflurane - 7 = righting, 15 = rotarod
Isoflurane - 10 = righting, 21 = rotarod
Halothane - 19 = righting, 40 = rotarod
What does the vaporiser do?
Deliver precise conc of anaesthetic, even when temp and rate of gas flow changed
How do you dispose of unused anaesthetics?
Inhalant = return liquid anaesthetic to original bottle
Injectable = sharps, may be special control
What do you do with animals after surgery?
- Put animal in bedding in incubator (not sawdust)
- After normal, put in warm recovery area (30-35C until animal conscious, maintain 35 for neonates, 25-30C for small rodents, 25C for larger animals. Reduce as they regain normal activity)
- Don’t need to give O2 but monitor respiration and keep animal on sides/chests
-Can have food+ water after moving normall and recovered - Assess for pain, maybe give NSAID
