Premed and sedation drugs Flashcards
Describe the ideal anaesthesia
Achieves the triad
Smooth induction and recovery
Minimal effect on body systems
How do we achieve the ideal anaesthesia?
Use a combination of drugs
Reduces the dose required of each individual drug
Therefore likelihood of side effects is reduced
Synergistic effect (1 + 1 > 2)
Anaesthetic protocol
What are the anaesthetic protocol stages?
Pre-medication (pre-med)
Induction
Maintenance
(Sedation)
What are the aims of pre-medication?
Calm the patient
Reduce the total dose of anaesthetic drugs needed
Relieve pain
To allow a smooth recovery
Reduce autonomic side effects
To reduce other side effects of anaesthesia
Give examples of pre-meds used
Phenothiazines
Opioids
Benzodiazepines
α-2 agonists
Anti-muscarinics (anti-cholinergics)
Butyrophenones
(Non-steroidal anti-inflammatories(NSAIDs))
(Ketamine)
Describe Phenothiazines
Acepromazine
Generally used in combination with an opioid
Effects: Aggression & seizures
Problems: Bracycephalics and boxers
Describe opiods
Bind to specific receptors in CNS to block pain signals
Pure agonist / partial agonist / pure antagonist
Partial agonists tend to bind most strongly to receptor sites
Compete for the same sites if given together (theoretically)
Describe Benzodiazepines
Diazepam and midazolam
Describe a-2 agonists
Effects:
Profound sedation
Reduces total anaesthetic dose (by 50% or more)
Muscle relaxation
Gives visceral analgesia
Examples:
Medetomidine, xylazine, dexmedetomidine
What are some potential problems with a-2 agonists?
Problems: Profound cardiovascular effects Vomiting Diuresis Hyperglycaemia Abortion Unreliable on its own for sedation
When may a-2 agonists be used?
alone or with opioids for pre-meds
at higher doses for sedation (e.g. cleaning ears) and if used with an opioid provide enough analgesia for minor wound repair.
The effects are variable, may wake unexpectedly, noise sensitive. Beware !
In combination with an opioid and ketamine for general anaesthesia.
May be given iv or im. The sc route is less reliable. Can also be absorbed across mms so take care when handling!
Medetomidine and dexmedetomidine can be reversed with Atipamezole
Describe Anti-muscarinics
Effects: Block parasympathetic system Prevent bradycardia Reduce respiratory secretions Reduce salivation Example: Atropine Glycopyrrolate
What are some potential problems with Anti-muscarinics?
May cause tachycardia
Pupillary dilation
Cause dry mouth
Boxers and other brachycephalic breeds?
Enucleation involving traction on the eyeball?
Laryngeal surgery?
Describe Butyrophenones
Only one in veterinary use is Fluanisone
in Hypnorm, licensed for rabbits, in combination with the opioid Fentanyl
“neuroleptanalgesia”
tranquilliser (neuroleptic) combined with a potent analgesic (opioid) to give heavy sedation or anaesthesia.
Describe NSAID’s
Analgesic Often considered part of a pre-med Sometimes contentious issue between vets… Disadvantage Reduces renal blood flow Examples Carprofen (Rimadyl) Ketoprofen (Ketofen) Meloxicam (Metacam)
