Premedication, analgesia, and anaesthetic Flashcards
what is the purpose of pre-medication?
- restraint
- reduce anxiety or stress
- achieve balanced anaesthesia
- reduction in dose of induction
what is balanced anaesthesia?
the use of multiple anaesthetic drugs in combination to provide general anaesthesia
what are some premedicants?
- phenothiazine
- alpha 2 adrenergic agonist
- alpha 2 adrenergic antagonist
what is a phenotiazines?
- acepromazine
what are some alpha 2 adrenergic agonist?
- medetomidine
- dexmedetomidine
- xylazine
what is an alpha 2 adrenergic antagonist?
atipamazole
what are some advantages of acepromazine?
- works well with opioids to product neuroleptanalgesia
- long lasting - 6 hours
- anti-arrhythmic action
- IM, SC or slow IV
- anti-emetic
what are some disadvantages of acepromazine?
- slow onset
- no analgesic effect
- poor muscle relaxation
- ceiling effect in large breeds
- hypotension
what are some advantages of alpha 2 adrenergic agonist?
- profound sedation
- good muscle relaxation
- profound drug sparing effect
- peripheral vasoconstriction reduces heat loss
- rapid recoveries
- given IM, IV, or SC
what are some disadvantages of alpha 2 adrenergic agonist?
- significant cardiovascular depression
- not suitable for severe liver disease
- can cause vomiting
- analgesic effect is reversed by atipamazole
- hypertension
what are some advantages of benzodiazepines?
- good sedation in sick/young animals
- minimal cardiovascular effects
- good sedation if used in an opioid
- anti-epileptic
- given IM, slow IV or SC
what are some disadvantages of benzodiazepines?
- minimal sedation in healthy animals
- can cause excitement
- muscle relaxation may impair breathing effort
- cannot be given in an infusion as they are absorbed in plastic
what are some classes of analgesics?
- opiates
- NSAIDS
- alpha 2
what are three types of pain?
- physiological (localised and appropriate)
- inflammatory (tissue damage associated with trauma or surgery)
- neuropathic (damage to the nervous system)
what is a noxious stimulus?
something that causes tissue damage
what is nociception?
the processing of noxious stimuli which activates nociceptors and their pathways
what is a pain pathway?
after repeated noxious stimulus has triggered the nociceptive pathway, the site of injury and surrounding tissues become highly sensitive to pain (wind up)
what is pre-emptive analgesia?
administering analgesics before the onset of noxious stimuli such as surgery
what are pure agonists?
occupy and strongly stimulate the sites and thus have a stronger effect
what are partial agonists?
occupy but don’t fully stimulate the sites
what enzymes do NSAIDS interfere with?
the cyclo-oxygenases (COX-1 + COX-2)
what are some side effects of NSAIDS?
- gastric ulceration
- renal damage
what are some ways to induce anaesthesia?
- intravenously
- intramuscularly
- via mask or induction chamber
what is propofol?
- induction agent
- quickly distributed - lasts 10-15 mins
- doesn’t cause arrhythmias
- can be given incrementally
- suitable for TIVA or PIVA
what are some disadvantages of propofol?
- causes excitement
- extensor rigidity
- causes brief apnoea when injection
- causes resp and cardiovascular depression
what is alfaxalone?
- steroid inducing agent
- most predictable when given IV (10 mins surgical anaesthesia)
- high/wide therapeutic index
- can be given incrementally
- causes minimal respiratory and cardiovascular depression
- TIVA and PIVA
what is ketamine?
- dissociative anaesthetic
- induces a feeling of separation
- good analgesic
- causes muscle hypertonicity
- causes a rise in HR and BP
how can anaesthesia be maintained?
- inhalant agents alone
- TIVA
- PIVA
- Injectable agents given IM
what does PIVA stand for?
partial intravenous anaesthesia
what does MAC stand for?
minimum alveolar concentration
what are some factors for isoflurane?
- non-flammable
- good muscle relaxation
- non-explosive
- smell is poorly tolerated
what are some factors for sevoflurane?
- less soluble than iso (quicker induction and recovery)
- better tolerated by patients
- less potent than iso
what is allodynia?
pain from a stimulus that does not normally provoke pain
what is hyperalgesia?
increased sensitivity to pain
what is multimodal analgesia?
more than one class of analgesic that target different receptors along the pain pathway
what is central sensitisation?
a state in which the central nervous system amplifies sensory input
what is local anaesthetic?
a temporary interruption in nerve conduction in sensory and motor nerves without loss of consciousness
what is neuroleptanalgesia?
provides a combination of deep sedation and analgesia by a synergistic combination of a neurolept and a narcotic analgesic
