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26 Cards in this Set
- Front
- Back
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What are the benefits for using local anaesthetics? |
-Reduces dose of other anaethetic drugs -Multimodalal analgesia -Pre - emptive analgesia -Diagnosis (equine) - |
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What are some examples of local anaesthetics? |
-Lidocaine = Intubeaze -Procaine = Wilcain Mepivacaine = Intra - epicaine Lidocaine + prilocaine = EMLA cream |
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How do local anaesthetics work? |
-Prvents transmission of nerve impulses ( by blocking sodium channels) -Sensory nerves affected at lower doses than motor nerves -Eventually absorbed into circulation - some faster than others -Adrenaline may be added to cause local vasoconstriction & slow absorption |
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What are the potential problems with local anaesthetics? |
-Toxicity; CNS & cardiac -Also blocks motor function -Thought that adrenaline may delay wound healing -Duration of action |
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What are the problems with toxicity with local anaesthetics? |
-CNS = can cross the blood brain barrier, at lower levels cause sedation / analgesia / anticonvulsant & seizures -Cardiovascular = slow myocardial conduction, cause peripheral vasodilation, cause bradycardia, hypotension & possible arrest -Cats more susceptible |
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What are the techniques when using local anaesthetics via topical use? |
-Applied to skin or mm -Minims (proxymetacaine) useful for examining the eyes -Intubeaze (lidocaine) for larynx in cats -EMLA can be used on the skin; requires 30 - 60 mins to take effect, good for rabbit ears |
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What are the techniques when using local anaesthetics via infiltration? |
-Area where anaesthesia required is infiltrated with local anaesthetic +/ - adrenaline -Dilute with NaCl (0.9%), helps avoid overdose -Wound soaker catheters |
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What are the techniques when using local anaesthetics via regional? |
-Nerve supply to an area or region is blocked; Brachial plexus, intercostal, maxillary / mandibular, epidural |
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What is brachial plexus? |
-Local anaesthesia is infiltrated around the nerves of the brachial plexus -Useful for surgery on the foreleg -Risk of haemorrhage / damage to brachial plexus |
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When are intercostal local anaesthetics used? |
-Pain relief after surgery/ trauma |
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When are the maxillary / mandibular local anaesthetics used ? |
-Dental extractions -Trauma rostral to injection site |
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When are intrasynovial local anaesthetics used? |
-Following joint surgery / arthroscopy -Injected at the end of surgery so not flushed out |
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When are intravenous local anaesthetics used? |
-Tend to be used ONLY in cattle -Tourniquets applied to proximal limb when vein injected with local anaesthetic |
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When are intrapleural local anaesthetic used? |
-Provide analgesia following thoracotomy or rib trauma -Given via chest drain if in place or butterfly catheter |
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When would an epidural local anaesthetic be used? |
-Injected between the Dura (outer layer of meninges) & vertebral canal to anaesthetise spinal nerves as they leave the cord Between the L7 - S1 in anaesthetised patient |
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When would paravertebral local anaesthetic be used? |
-Cattle for flank surgery |
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When are neuromuscular blocking agents used? |
-Muscle relaxation part of the triad of anaesthesia
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What are the advantages of NMBAs? |
-Provides muscle relaxation -Prevents movement -Whole body -Reduce need for high concentration of inhalational agents |
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What are the problems with NMBAs? |
-Monitoring depth of anaesthesia -Prevents movement of respiratory muscles |
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When are NMBAs indicated for use? |
-Intraocular surgery -Facilitate IPPV -Laparotomy -Cardiovascularly unstable patients |
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How do NMBAs work? |
-Blocks the action potential at the neuromuscular junction -Two types |
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What are the two types of NMBAs? |
-Depolarising -Non - depolarising |
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-How do depolarising NMBAs work? |
-Bind reversibly to the Ach receptor -Initial muscle contraction followed by relaxation |
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How do non - depolarising NMBAs work? |
-Bind reversibly to Ach receptor but do not cause muscle contraction -used in veterinary practice |
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How are NMBAS reversed? |
-Modern agents short acting so often left to "wear - off" -Reversed with ant- acetylcholonesterase (neostigmine or edrophonium) -Competitibe antagonist so effect so can be overcome by increasing the concentration of the agonist |
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How do you monitor animals under NMBAs? |
-Requires a peripheral nerve stimulator -Need to attach & check placement BEFORE administer the NMBA -Peripheral nerve stimulator gives information on how effective the block is -HR & pupil dilation monitored closely - indicator of anaesthetic depth |
