Clinical Induction of Anaesthesia Flashcards
Induction of anaesthesia definition
the administration of a drug or combo of drugs at the beginning of an anaesthetic that results in the unconsciousness and allows you to intubate the patient
How fast does it take for induction of anaesthesia occur?
Thiopentone - 20-30 secs (1 circulation time)
All other drugs - about 2 mins (4 circulation times)
What are the methods of inducing anaesthesia?
- IV injection given to effect
- IM injection
- Inhalation/mask or chamber
How long does IV injection of induction take?
up to 2 minutes
How long does IM injection of induction of anaesthesia take?
5-30 mins
Why is inhalation induction of anaesthesia not recommended?
- stressful for P
- poor for environment (world) & working environment
What are a few things to remember about induction?
- IV & IM induction of anaesthesia is irreversible
- Ensure you administer the correct dose (based on body weight)
- Have a ‘Plan B’ in case of problems
- Monitor the patient’s vitals
- Be ready for intubation
- have O2 source
What characteristics would make the ideal agent for induction of anaesthesia?
- has rapid onset of action
- minimum alteration to HR or BP
- minimum post-induction apnoea
- rapid & smooth recovery w/ no hangover
- provides analgesia
- provides good muscle relaxation
- minimal organ toxicity
- no venous/injection issues
- suitable physical properties
Which drugs have a rapid onset of action (one ‘arm-to-brain’ circulation time - 30 seconds) for induction?
Thiopentone
Which induction drugs have minimum alterations to HR or BP?
Alfaxalone
Ketamine
Which induction agents have minimum post-induction apnoea?
Alfaxalone & ketamine
Propofol & Thiopentone especially
When propofol is given too much too fast during induction, what occurs?
signs of an overdose = post-induction apnoea
What induction drugs have a rapid & smooth recovery w/ no hangover?
Propofol
What induction agents provide analgesia?
Ketamine
What induction drugs provide good muscle relaxation?
Alfaxalone
Propofol
Thiopentone
What induction drugs cause minimal organ toxicity?
Alfaxalone
Propofol
Ketamine
Thiopentone
What is a caution with using propofol in cats?
Repeated anaesthesia can cause Heinz Body anaemia
What induction drugs cause no venous/injection issues?
Alfaxalone
Ketamine
Propofol - some preparations
What induction drugs have suitable physical properties?
alfaxalone
Ketamine
Thiopentone
What is marketed as the gold standard medication of induction of anaesthesia?
Propofol
Why is propofol a popular induction agent (aka advantages)?
- slow “to effect” induction w/o excitement
- rapid recovery from anaesthesia
- non-cumulative; suitable for TIVA
- suitable for thin dogs & sighthounds
- no perivascular damage
- not arrhythmogenic
- affordable
What are the disadvantages of propofol?
- CVS depression
- Respiratory depression
- hypercapnia if used for TIVA
- pain on injection, short-lived
- propofol ‘twitches’/myoclonus
- shelf-life of preservative-free formulation very short (6-8 hrs)
- Propofol 28 (w/ preservative) not suitable for repeated admin/infusion due to preservative
What is a patient that the preservative form of propofol should not be used?
C-sections
What type of drug is ketamine?
Dissociative anaesthetic which dissociates mind & body
What signs of anaesthetic depth are used with ketamine?
- active pharyngeal & laryngeal reflexes
- open, central eye
- nystagmus (equine)
- increased muscle tone
- hallucinations (humans)
Ketamine advantage?
Analgesic
Alfaxalone can be used for…
- induction of anaesthesia
- total intravenous anaesthesia (TIVA) as CRI
- Sedation (IM)
Alfaxalone is a … anaesthetic
steroid
Injectable anaesthesia is made up by…
IM injections
repeated IV injections or top-ups
TIVA
What drug combintions are used in small animal practice for injectable anaesthesia?
- Medetomidine & ketamine +/- butorphanol IM
- Ketamine & diazepam IV +/- top-ups
- propofol IV, to effect
- alfaxalone IV, to effect
What drug combinations are used in equine practice for injectable anaesthesia?
- A-2 agonist & ketamine +/- butorphanol IV
- Triple Drip (GGE, Xylazine, Ketamine)
What are the advantages of IM/IV anaesthetic techniques?
- useful for quick procedures
- useful for wild animals
- no expensive equipment required
- no operating room pollution
- can reverse some agents
What are the disadvantages of using IM/IV anaesthetic techniques only?
- no return of anaesthetic agents
- easy to overdose
- variable onset of action w/ IM inj
- may be dfficult to control depth
- resp depression common
- may be difficult to prolong anaesthesia safely
- IV injection may result in perivascular leakage
- no ETT/airway protection
- no anaesthetic machine or O2
- inadeq monitoring of P
- not suitable for high-risk P w/o fluids & O2
- cannot resuscitate P if no airway protection/O2 support available
What considerations should be taken into account before using IM/IV techniques of anaesthesia?
- use combo of drugs if possible
- use drugs w/ reversal agents
- monitor P throughout procedure, incl post-op
- provide analgesia, O2, fluid therapy
TIVA is used to
reduce inhalant anaesthetics when possible
TIVA can be
a single agent or combo of IV agents
what drugs are used for dogs in TIVA admin?
- Propofol & opioid (fentanyl, remifentanil) +/- NMB
- Alfaxalone & opioid
What drugs are used for horses in TIVA admin?
- Ketamine, alpha-2, guaifenesin (‘triple drip’)
