Local Anaesthetics & Muscle Relaxants Flashcards
(29 cards)
What are the advantages of using GA?
-convenience and practicality
-rapid loss of consciousness
-wide surgical field is available
-wide variety of surgical procedures can be performed
What are the disadvantages of using GA?
-need for restraint of the patient prior to induction
-requirement for skilled administration and continued motoring of patient
-a degree of cardiovascular and respiratory depression is possible
Why do we use local anaesthesia?
-targeted analgesia
-for high risk patients where GA not appropriate
-part of multi-modal analgesia approach intra-op
-pre-emptive analgesia
How does local anaesthesia work?
-blocks sodium channels at nerve endings
-which then blocks nerve impulse conduction
-sensory neurons are more sensitive to their effects
In what order does sensation disappear?
-pain
-cold
-warmth
-touch
-pressure
How can local anaesthesia be administered?
-local infiltration, injection into superficial tissues
-regional anaesthesia, injected into nerve that supplies specific region
-spinal
-transmucosal, absorbed across MM
-transcutaneous
Give examples of local anaesthesia for clinical use?
-topical (intubation or Elma cream)
-subcut infiltration (blockers)
-nerve blocks
-epidurals
-intravenous
-splash blocks
-anti arrhythmic (lidocaine for IV)
What are 5 examples of local anaesthetic drugs?
Lignocaine
Bupivacaine
Amethocaine
Lidocaine
Benzocaine
What effects do local anaesthesia drugs have?
-little sedative effects
-few effects on CVS
-few effects on respiratory system
Describe the procedure for infiltration?
-clip area to be treated
-aseptic prep
-use small gauge needle to prevent tissue damage
-inject small amount
-onset of action usually within 3-5mins
-test effectiveness of block by pricking skin
What does the duration of effect depend on?
-the drug used
-the rate of absorption (which is affected by route given)
What do regional nerve blocks do?
-range of techniques to reduce sensation to the face and head
What do regional blocks do?
-injected unto major nerve plexus or close to spinal cord
-cases blockage of relatively large area
How does regional epidural work?
-blocks sensation to caudal abdomen, pelvis, tail and perinium
-requires careful technique
How does regional spinal anaesthesia work?
-drugs injected into subarachnoid space where they mix with CSF
-deeper than epidural
Where can regional topical anaesthesia be used?
-eyes or cornea
-skin
-larynx
-urinary catheterisation
What are the risks of using local anaesthesia?
-may cause nerve damage or permanent loss of function
-can cause tissue irritation
-possible allergic reactions
-animals may chew area following recovery
-hypotension can occur
-use with careful in exotics and cats
What are muscle relaxants?
-they are neuromuscular blocking agents
What do muscle relaxants do?
-they interrupt transmission of impulses from motor nerve to muscle synapse
-acts at nicotinic receptors or block release of acetylcholine
What do depolsaring muscle relaxants do?
-cause initial surge at NMJ followed by refractory period where muscle does not respond
What are 2 examples of depolarising muscle relaxants?
Succinylcholine
Suxamethonium
What do non-depolarising muscle relaxants do?
-they block the receptors at the muscle end plates?
-can be reversed
Give 2 examples of non-depolarising muscle relaxants?
Vecuronium
Atracurium
How do non-depolarising muscle relaxants work?
-given by slow IV
-work within a few minutes
-paralyses skeletal muscles so patient is unable to move or respond to inadequate anaesthesia
-doesn’t affect consciousness as doesn’t cross blood brain barrier
