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With traumatic rib fracture/chest tube placement, where do you place bupivicaine in relation to injury site? How long will analgesia last at thoracic wall?
- 2-3 intercostal spaces before and after the injury
- analgesia for 4-6hr
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What cranial nerve is blocked for facial and dental blocks? Sensory or motor block? Major branches of concern?
- Trigeminal (5)
- sensory
- maxillary and mandibular
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What is desensitized when performing mental block?
- rostral mandible
- lower caninese and incisors
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What is desensitized with mandibular block?
- skin, mucosa,
- teeth of caudal and rostral mandible
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What is desensitized with infraorbital block?
upper lip, nose, upper rostral teeth
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What is desensitized with maxillary block?
caudal maxilla, premolars, molars
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What cranial nerve is blocked for ophthalmic surgery? Which branch? Sensory or motor?
- Facial (7)
- auriculopalpebral branch (motor to orbicularis oculi mm.)
- motor (so no analgesia, just immobilized/red. pressure)
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What cranial nerves are involved with retrobulbar block used for enucleation?
- optic (2), oculomotor (3)
- trigeminal (5) - ophthalmic branch
- abducens (6)
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What is important adverse effect to be aware of with retrobulbar block?
- subarachnoid injection (potentially fatal)
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What type of LA technique is used for digit amputation? which nerves are involved?
- ring block/ digital nerve block
- superficial branches of radial and median n., dorsal/palmar br. of ulnar n.
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Where is epidural injection placed? What is most common anatomical position?
- extradural space occupied by fat surrounding dura mater (outside spinal cord/inside spinal canal)
- L7-S1 = lumbosacral junction
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does epidural provide analgesia to genitalia, perineal area and pelvic viscera?
yes
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which drug is administered for epidural to thorax and forelimbs?
- morphine
- (NOT local anesthetics --> can block phrenic n.)
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does spinal cord extend further in dog or cat? why does this matter?
cat - planned epidural can become intrathecal/spinal injection --> need to be aware to half dose if this happens
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What are 3 advantages of spinal injection?
- Main DISadvantage?
- less systemic absorption
- lower dose required
- direct contact w/nerve roots
- disadvantage: in CSF so can migrate to brain
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what are the 'pops' felt when performing epidural?
needle piercing ligaments before entering epidural space --> loss of resistance indicates needle entered epidural space
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what is the most popular combination for epidural injection?
- morphine + lidocaine/bupivicaine
- (alpha2 is lipophilic - does not remain long/rapidly absorbed)
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Why are preservative free formulations needed for spinal/epidural administration?
additives can be neurotoxic
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Do local anesthetics cause sensory and motor block? what about opioids, ketamine, or alpha 2?
- LA= complete sensory and motor
- opioid = analgesia by blocking pain transmission, can only reduce to variable degree (incomplete)
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How long does morphine provide analgesia with epidural?
- 24 hours
- (it's hydrosoluble = stays at site, won't migrate fat of epidural space)
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what is risk of injecting epidural too fast?
excessive cranial migration
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If desired effect is to block right hind limb, what is common technique to ensure block of right side? Is this necessary?
- lay pt on right recumbency to prolong contact time with this side's nerve roots
- more likely that solution diffuses uniformly regardless of position
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What are some advantages of epidural anesthesia?
- relatively simple and inexpensive
- excellent analgesia and decr. anesthetic requirements
- prolonged analgesia good for extensive sx
- can be given before/after sx, prior to recovery of anesthesia
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how does epidural injection lead to hypotension? How can we compensate?
- block paravertebral sympathetic ganglia --> lose control of splanchnic vascular tone --> blood pools in viscera --> hypotension
- -can admin IV fluid bolus preemptively
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What is first sign of subarachnoid penetration that results in brain penetration?
- anisocoria (unequal pupil size) then mydriasis
- can result in marked respiratory depression
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What is an UNCOMMON complication that occurs when large volumes injected cause pressure change in epidural space?
bradycardia and cardiovascular depression (uncommon)
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What vessels are on the floor of the spinal canal? Which pt is puncture of this blood supply the most concerning?
- venous plexus
- patient with coagulopathy (epidural contraindicated in know coagulopathy patient)
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Why would epidural injection lead to incomplete block?
failed drug admin -lack of uniform diffusion due to injection speed/technique or anatomical variations or air bubble
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Why does epidural sometimes induce urinary retention?
temporary dysfunction of detrusor muslce or increased urethral sphincter tone
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What are some contraindications for epidural anesthesia?
- skin infection/dermatitis at injection site
- clotting problems
- septicemia
- fractured pelvis/spine (inflammation/distorted landmarks)
- pre-existing hypotension (only with LA)
- meningitis, CNS disorder, neurological dz
- (difficult in obese or discospondylitis)
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what is an indication to place epidural catheter in dog? How long can it be left in place?
- following thoracotomy or anything requiring prolonged analgesia (also done in horses)
- 48-72 hours post-op
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What is blocked with brachial plexus block? Where administered?
- below elbow (loss of motor and sensory) radial, ulnar, musculocutaneous, median and axillary
- C6,7,8 and T1 (medial to tip of shoulder)
- **not brachium
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What LA is a poor choice for Bier block?
bupivicaine - cardiotoxic due to systemic absorption when turniquet removed
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What are some indications for Bier block?
ruminant digital amputation/surgery (sometimes small animal)
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what are risks/complications of brachial plexus block?
- inadvertent IV injection --> LA toxicity
- subscapular hematoma if pierce large vessel
- pneumothorax
- nerve damage/paralysis -- lameness
- infection
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