Lecture 16 10/31/24 Flashcards
What are the goals of preemptive locoregional nerve blockade?
-block afferent sensory information
-prevent noxious stimulus from reaching CNS
-reduce need for systemic drugs
-reduce adverse drug effects
-promote pain-free and comfortable recovery
Which drugs are used for nerve blocks?
-opioids
-alpha2 adrenoceptor agonists
How can nerves be located for nerve blocks?
-blind injection
-nerve locator
-peripheral nerve stimulators
-ultrasound-guided blocks
What are the benefits to using a nerve locator?
-closer to the nerve
-more effective
-apply as little drug as possible
What are the characteristics of an electrical nerve stimulator?
-allows localization of the nerve
-uses variable current in the stimulating device
Which nerve blocks are done in the head area?
-ophthalmic n.
-auriculotemporal n.
-maxillary n.
-mandibular n.
-mental n.
-infraorbital n.
What are the branches of the trigeminal nerve?
-ophthalmic n.
-maxillary n.
-mandibular n.
What are the characteristics of the maxillary nerve block?
-middle branch of trigeminal n.
-blocks sensory innervation to entire upper dental arcade, soft palate, hard palate, and muzzle
How is the maxillary nerve blocked through the oral cavity?
-needle is introduced into the mucosa
-caudal to last molar
-injection at junction of hard and soft palate
How is the maxillary nerve blocked through the zygomatic arch?
at corner of the zygomatic arch and the caudal border of the maxilla
Which other approach can be used to block the maxillary nerve?
infraorbital canal
What are the characteristics of the infraorbital nerve block?
-branch of maxillary nerve
-blocks sensory innervation to rostral part of maxilla
-blocks anterior upper teeth, nose, and upper lip
What are the characteristics of the mandibular nerve block?
-blocks entire lower dental arcade, tongue, and lower lip
-blocks nerve as it enters mandibular foramen
-on medial surface of mandible
-foramen is palpated from inside mouth
-intraoral or extraoral approach
What are the characteristics of the mental nerve block?
-rostral continuation of mandibular nerve
-mental foramen located caudal and ventral to lower canine tooth
-blocks sensory innervation to rostral portion of mandible
-desensitizes lower incisors, canine teeth, and lower lip
How is the mental nerve block performed?
-mandibular labial frenulum is retracted ventrally
-needle is inserted into the rostral aspect
What are the characteristics of the brachial plexus?
-originates from C5, C6, C7, C8, and T1 (sometimes T2) spinal nerves
-gives rise to radial, ulnar, median, and musculocutaneous nerves
What are the techniques for an axillary brachial plexus block?
-RUMM block/at level of the arm
-digit nerve blocks over the digits
-regional intravenous block/lower extremities
What are the indications for axillary brachial plexus blocks?
elbow and distal procedures
What are the landmarks for an axillary brachial plexus block?
-medial to the shoulder
-direct needle toward the first rib
What are the indications for epidural anesthesia?
-cesarean section
-pelvic or hind limb surgery
-abdominal exploratory
-perineal or peri-anal procedures
What is the epidural space?
space between the vertebral column and the dura mater
What are the steps to finding the L-S junction?
-pull legs forward in ventral or lateral recumbency
-palpate iliac crests with first and third finger of non-dominant hand
-palpate L7 spinous process with pointer finger
-insert needle 45-60 deg. to the horizontal plane
Which layers must the needle pass through to reach the epidural space?
-skin
-SQ and interspinous ligament
-interarcuate ligament (pops)
What is the most common epidural medication combination?
bupivacaine and morphine
What are the characteristics of epidural morphine?
-full opioid agonist
-hydrophilic/poor lipid solubility; less systemic uptake
-onset around 60 minutes
-duration of 16-24 hours
-no motor blockade
What are the adverse effects of epidural anesthesia?
-hypotension
-urinary retention
-motor blockade in both pelvic limbs
-cranial migration
-cardiovascular and resp. depression
-pruritus
-abnormal hair regrowth
Which nerve blocks are used for the hind limbs?
-femoral: L4-L6
-sciatic: L6-S3
How is the sciatic nerve block approached?
between ischiatic tuberosity and greater trochanter
What is the use of the femoral nerve block?
block craniomedial innervation of the thigh
