Pre-medication Flashcards
Name the 5 groups of premedication
Phenothiazine, Alpha-2-agonists, Benzodiazepines, Opioid Analgesics, Anti-muscarinics
Name a Phenothiazine
Acepromazine (ACP)
What patients are sensitive or resistant to ACP?
Large dogs are sensitive to ACP; Small dogs and Cats are resistant to ACP
Describe the properties of phenothiazines?
Dopamine receptor antagonist
Sedative/tranquiliser, but has NO analgesia
What are the advantages of Phenothiazines?
Anti-histamine
Anti-emetic
Anti-arrhythmic
Smooth muscle spasmolytic
What are the disadvantages of phenothiazines?
Predisposes hypothermia Hypotension Peripheral vasodilation Decreased seizure threshold Slow onset (30-40minutes) Long duration
What are the properties of Alpha-2-agonists?
Bind to alpha 2 receptors in the brain
Provide sedation AND analgesia
For healthy animals
Giver 2 examples of alpha 2 agonists
Medetomidine and Dexmedetomidine
What are the advantages of alpha 2 agonist?
Provides analgesia Drug sparing effect Muscle relaxation Reversible - using alpha 2 antagonist Atipamezole Dose-dependant sedation
What are the disadvantages of alpha 2 agonists?
Hypertension Vasoconstriction Vomiting Impaired Thermoregulation CVS depression ( lowers CO and HR) Respiratory Depression (can lead to apnoea)
What are the properties of Benzodiazepines?
Binds to, and enhances GABBA neurotransmitter receptors in CNS.
It is a tranquiliser (reduces anxiety) but not really a sedative (which reduces consciousness)
Give 2 examples of Benzodiazepines
Midazolam and Diazepam
What are the advantages of benzodiazepines?
Reduces anxiety
Its safe (i.e. has a high therapeutic index)
Muscle relaxant
Minimal cardiopulmonary effects (safe for very sick patients)
Prolong and enhance effects of other anaesthetics
Anti-epileptic (diazepam)
What are the disadvantages of benzodiazepines?
Causes excitement in healthy animals (when used alone)
Risk of liver necrosis
Unpredictable
Diazepam is painful IM
What are the properties of opioid analgesics?
Binds to mu receptors in the brain
Can be reversed with Naloxone
Give 2 examples of Opioid Analgesics? What type of agonist are they and what are they used for?
Buprenorphine - partial agonist - for mild to mod pain
Methadone - full agonist - for mod to severe pain
What are the advantages of using opioid analgesics as pre-meds?
Can provide sedation in non-painful or very sick animals
Reduces the dose of induction drug required
Dose-dependant analgesia
CO remains good
What are the disadvantages of using opioid analgesics as pre-meds?
Excitation in overdose If overdose, can cause profound respiratory depression GI effects (e.g. vomiting) Urinary retention Anti-tussive effect
What are the properties of Anti-muscarinics?
Parasympathetic antagonist
Inhibit acetylcholine receptors
They increase HR - used in surgeries where there is pushing/pulling on things can trigger vagal reflex (which would decrease HR)
Give examples of an Anti-muscarinic?
Atropine
Glycopyrrolate
What are the advantages of Anti-muscarinics?
Controls intra-operative bradycardia
Reduces salivation and bronchial secretions (therefore reduces the risk of aspiration pneumonia)
Protects against bradycardia during reversal of NMBA
What are the disadvantages of Anti-muscarinics?
Cause arrhythmias
Cause diminished GI activity
Pupil dilation leading to visual disturbance
Thickens bronchial secretions
Increases HR, Increases metabolic rate, Increases myocardial O2 consumptions
