Pre-Medication Flashcards
Why do we use pre-medications?
-calm patient and reduce anxiety in pre op period
-provides sedation, making induction more smooth
-provides analgesia
-reduces dose of induction and maintenance agents required thereby improving safety
-smoother recovery is expected
What are the 3 golden rules during premed?
-correct dose for each individual
-quiet environment
-enough time for the drug to take effect
What does phenothiazines do, and give an example?
-provide tranquillisation (calming), with sedation at higher doses
-they do not provide analgesia
-eg, acetylpromazine (ACP)
What are phenothiazine characteristics?
-tranquillise/sedation
-long duration of action
-smooth recovery
-relatively safe
-anti-emetic and smooth muscle relaxation
-mild anti-histamine effect and anti-arrhythmic
-bigger animals need smaller doses as are more sensitive
What are phenothiazines side effects?
-causes vasodilation and will lead to hypotension
-must take care with dehydrated/hypovolaemic patients
-may cause hypothermia
-decreased seizure threshold
What are pehothiazine negatives?
-slow to peak effect
-no analgesia
-unpredictable sedation
What do alpha 2 adenoceptor agonists do, and give examples?
-drugs that bind alpha 2 receptors in the brain and spinal cord
-blocks the transmission of nociceptive impulses
-provides sedation and analgesia
-complete reversal of effects is possible
-eg, Medetomidine
-eg, dexmedetomidine
What are the benefits of using alpha 2 adrenoceptor agonists?
-duration and level of sedation is dose dependant
-profound drug sparing effect
-provides muscle relaxation and analgesia
-complete reversal of effects is possible
What side effects do alpha 2 adrenoceptor agonists have?
-profound effects on CVS
-causes vasoconstriction
-slows heart rate
-reduces liver blood flow and may cause vomiting
-avoid in patients with cardiovascular disease and liver disease
What do benzodiazepines do, and give examples?
-tranquillisers
-do not provide a deep sedation
-eg, diazepam
-eg, midazolam
What are the benefits of benzodiazepines?
-safe
-has minimal effects on CVS ad resp systems
-anti-epileptic actions
What are the negatives of benzodiazepines?
-can be unpredictable action
-not a sufficient premed if used alone in healthy animals
-diazepam is painful by IM injection g
Is an opioid an analgesic?
Yes
How do opioids work?
-they combine with specific opioid receptors in the brain and spinal cord
-they decrease the transmission of noxious stimuli (pain across these receptors)
What are characteristics of full agonist opioids?
-stronger
-produces a maximal effect as it binds all receptors
-can be topped up to increase analgesic effect
-for moderate to severe pain
What are examples of full agonist opioids ?
Morphine
Fentanyl
Methadone
What are characteristics of partial agonist opioids?
-can’t induce a maximal response
-can’t be topped up
-for mild to moderate pain
What is an example of a partial agonist opiod?
Buprenorphine
What are opioid antagonists?
-they antagonise the effects of agonists
-can be used as an antidote in cases of overdose
What is an example of an opioid antagonist?
Naloxone
What effects do opioids have on patients?
-provides analgesia, euphoria and sedation
-has little effect on respiration at correct dose
-has little effect on CVS
-has drug sparing effect
What negatives do opioids have on patients?
-high doses lead to profound respiratory depression
-can cause vomiting
-constipation
-can cause urinary retention
What do anti-muscarinics do?
-decrease parasympathetic tone by blocking transmission via acetyl choline
-they antagonise the parasympathetic nervous system
Give 2 examples of anti-muscarinics?
Atropine
Glycopyrrolate
What are the benefits of using anti-muscarinics?
-reduces sedation
-reduces bronchial secretion
-counteracts bradycardia
-decreases salivation
What are the negatives of anti-muscrainics?
-can cause increased HR and metabolic rate
-may cause arrhythmias
-thickens bronchial secretions
-can reduce GI function
-pupil dilation which leads to visual disturbance
