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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
What cranial nerve is blocked for facial and dental blocks? Sensory or motor block? Major branches of concern?
- Trigeminal (5)
- maxillary and mandibular
What is desensitized when performing mental block?
- rostral mandible
- lower caninese and incisors
What is desensitized with mandibular block?
- skin, mucosa,
- teeth of caudal and rostral mandible
What is desensitized with infraorbital block?
upper lip, nose, upper rostral teeth
What is desensitized with maxillary block?
caudal maxilla, premolars, molars
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)
What cranial nerves are involved with retrobulbar block used for enucleation?
- optic (2), oculomotor (3)
- trigeminal (5) - ophthalmic branch
- abducens (6)
What is important adverse effect to be aware of with retrobulbar block?
- subarachnoid injection (potentially fatal)
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.
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
does epidural provide analgesia to genitalia, perineal area and pelvic viscera?
which drug is administered for epidural to thorax and forelimbs?
- (NOT local anesthetics --> can block phrenic n.)
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
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
what are the 'pops' felt when performing epidural?
needle piercing ligaments before entering epidural space --> loss of resistance indicates needle entered epidural space
what is the most popular combination for epidural injection?
- morphine + lidocaine/bupivicaine
- (alpha2 is lipophilic - does not remain long/rapidly absorbed)
Why are preservative free formulations needed for spinal/epidural administration?
additives can be neurotoxic
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)
How long does morphine provide analgesia with epidural?
- 24 hours
- (it's hydrosoluble = stays at site, won't migrate fat of epidural space)
what is risk of injecting epidural too fast?
excessive cranial migration
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
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
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
What is first sign of subarachnoid penetration that results in brain penetration?
- anisocoria (unequal pupil size) then mydriasis
- can result in marked respiratory depression
What is an UNCOMMON complication that occurs when large volumes injected cause pressure change in epidural space?
bradycardia and cardiovascular depression (uncommon)
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)
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
Why does epidural sometimes induce urinary retention?
temporary dysfunction of detrusor muslce or increased urethral sphincter tone
What are some contraindications for epidural anesthesia?
- skin infection/dermatitis at injection site
- clotting problems
- fractured pelvis/spine (inflammation/distorted landmarks)
- pre-existing hypotension (only with LA)
- meningitis, CNS disorder, neurological dz
- (difficult in obese or discospondylitis)
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
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
What LA is a poor choice for Bier block?
bupivicaine - cardiotoxic due to systemic absorption when turniquet removed
What are some indications for Bier block?
ruminant digital amputation/surgery (sometimes small animal)
what are risks/complications of brachial plexus block?
- inadvertent IV injection --> LA toxicity
- subscapular hematoma if pierce large vessel
- nerve damage/paralysis -- lameness