Term
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Definition
-loss of sensation due to blockade of AP transmission in n. fibres
-cause changes in nerve memb. that prevent depol. and thsu block propagation - "membrane stabilisation"
- reversible and not associated w. loss of consciousness |
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Term
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Definition
| -most likely to occur due to OD so much more common in SA c.f. LA |
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Term
| Factors affecting systemic toxicity of LA |
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Definition
-site of injection - vasc. sites lead to rapid absorption into vasc. system - inadvertent IV inj. is a risk - always check
-drug used
-addition of AD - causes local vasoconstriction resulting in slow absorption w. dec. peak concentration of up to 20-50% |
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Term
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Definition
-slowing of conduction of myocardium
-myocardial depression
-peripheral vasodil.
...results in...
-bradycardia, hypotension and poss. cardiac arrest
NB: bupivicaine cardiotoxicity > lidocaine |
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Term
| Mgmt of CV effects associated w. LA |
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Definition
| -symptomatic - provision of fluid therapy to counter hypotension is important |
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Term
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Definition
-agents are lipid soluble low molecular wt. so readily cross BBB
-sub-toxic dose = anticonvulsants, sedatives, analgesics
-higher conc. = convulsions and generalised CNS depression |
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Term
| Mgmt of CNS toxcitiy associated w. LA |
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Definition
-symptomatic
e.g. anticonvulsants or induce general anaesthesia
-careful monitoring of physiological systems in case generalised CNS depression |
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Term
| Tissue effects of LA injection |
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Definition
-if needle punctures / penetrates b.v. = haematoma - always draw back to check!
(not a huge problem but can be painful)
-if inject into n. rather than around it, results in nerve damage - would be high R to admin and so should be able to tell
-vasodilation is a s. effect of LA inj |
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Term
| Small animal LA technique |
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Definition
-currently LA in small animals is often neglected, but is useful
-can reduce the dose of other anaes. drugs required for anaes. maintenance and contributes to multi-modal anaes.
-can use specific nerve blocks to prevent relay of nociceptive info can provide pre-emptive analgesia and prevent / dec. development of central sensitisation
-almost always in combo. w. GA |
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Term
| Decr. the risk of complications associated w. LA in small animals |
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Definition
-weigh the animal when calculating the dose, don't guess!
-calculate safe max. dose and do not exceed this - if you need more drug for wider distribution then dilute w. saline
-use appropriate size needle and syringes - minimise tissue trauma during inj. and allows accurate dosing
-check for inadvertent intravasc. inj |
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Term
| Local anaes / analgesic techniques |
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Definition
-topical / transmucosal
-infiltration
-regional
-epidural
-dental / maxillary and mandibular blocks
-also digital n. block, ring block (distal limb procedures) |
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Term
| Topical anaesthesia (transmucosal) |
|
Definition
-application of LA to MM produces rapid analgesia, but usually small depth (1-2mm)
-absorption through the skin is poor - EMLA cream (lidocaine and prilocaine) IS capable of producing anaes. if applied to the skin and covered w. non-permeable dressing |
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Term
| Topical anaesthesia (transmucosal) - common areas for admin |
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Definition
-cornea for ocular exams
-nasal passages
-larynx during intuabtion |
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Term
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Definition
-common in vet practice
-safe, reliable and does not require extensive experience |
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Term
| Infiltration anaesthesia admin |
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Definition
-use sterile, sharp needles
-if inj. are made at the periphery of each weal then only the one needle prick is felt
-LA should be dilutes w. 0.9%NaCl |
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Term
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Definition
| -nerve supply to a specific area or region is blocked where the nn. are easily accessible from the skin (must be readily palpable and floow a fixed course next to identifiable structures) |
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Term
| Common regional anaesthesia sites |
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Definition
-Abdominal surgery in cattle - paravertebral block
-Disbudding / de-horning - corneal nn. block |
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Term
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Definition
-lumbosacral epidural anaes. may be used to provide analgesia for all procedures cd. to the thoracolumbar junction
-esp. useful for orthopaedic procedures in the hindquarters |
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Term
| Epidural anaesthesia technique |
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Definition
| -use combo. of preservative-free morphine and bupivicaine |
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Term
| Dental / maxillary and mandibular blocks |
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Definition
| -can be blocked as they exit infra-orbital and mental foramens respectively, or blocked more proximally to povide wider area of analgesia |
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Term
| Large animal LA general use |
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Definition
-many large animal surgical procedures can be carried out safely and humanly "on farm" using LA w. restraint and mild sedation w. the animal in a standing position
-means dont need GA which is associated w. complications in large animals and often not licensed |
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Term
| Regional techniques over local infiltration techniques |
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Definition
In regional techniques
- target inj. of LA around nerve trunk so lower vol of drug is required
-no distortion of tissues at surgical site
-loss of sensory innervation is targeted to required area, so body area affected is ltd
-animal can remain standing
-generally considered to be more effective |
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Term
| Licensed LA agent for use in food-producing animals |
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Definition
-ONLY Procaine hydrochloride (w. AD for vasoconstriction - decr. systemic absorption and so prolong duration of action - care w. end arterial sites e.g. teats, penis)
-is CI for epidural and IV inj but is used routinely for both w/o problems
-not quick onset, so check there is adequate desensitisation before proceeding!
-0 meat and milk withdrawal period |
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