Locoregional Anes SA & LA Flashcards
typical LA techniques
topical
SQ
Line block
wound soaker catheter
Topical anesthesia
EMLA cream (2.5% lidocaine + 2.5% prilocaine)
- 60 min before full onset, occlusive dressing
- IVC placement
Lidocaine patch (5% lidocaine)
- analgesic effect, not complete block
- placed on incision after closure
Ophthalmic
- Tetracaine or proparacine
Laryngeal
- 0.1 mL 2% lidocaine (feline intubation)
- topical to arytenoids
SQ
use for wounds, masses, skin biopsy
- Ventral midline line block*
- infliltrate SQ & muscle layers
- Wound soaker catheter*
- placed during sx, deep aspect close to visualized nerves
- delivers consisten 7 prolonged (1-2d) analgesia
- used for TECA, Amputation , oncologic sx, lg wound closure
IVRA aka “Bier block”
- used for distal extremity
- procedure 60-90 mL
- complications: tourniquet pain, ischemia/nerve inj, limb swelling, hematoma, LA toxicity
peripheral nerve blocks - head
Retrobulbar block
Maxillary n. block
Infraorbital n. block
Inferior alveolar n. block
Mental n. block
retrobulbar block
Indications:
- Enucleation
- Evisceration/prosthesis
- Intraocular surgery
Nerves affected:
- CN II, III, IV, V, VI, ciliary ganglion (parasympathetic)
Advantages:
- Post-op analgesia
- Globe immobility during surgery
- Decreased anesthetic and NMBD requirements
Complications:
- Retrobulbar hemorrhage
- Damage to optic nerve, extraocular mm.
- Globe penetration
- Intravascular injection
- Intrathecal injection (into optic nerve/subarachnoid space)
Preferred technique:
Inferior-temporal palpebral
- High resistance to injection indicates positioning within optic nerve sheath – injection may be fatal
Peripheral nerve blocks - thoracic limb
Cervical paravertebral block
Brachial plexus block
RUMM block
“declaw” block – distal radial, ulnar, median
cervical paravertbral block
- Less common block
- Technically difficult
- Anesthesia for entire thoracic limb incl. scapula and shoulder joint
- Ventral branches of C6, C7, C8, and T1 spinal nerves, proximal to brachial plexus
Brachial plexus
Anesthesia distal to and including the elbow
RUMM block
- Anesthesia for “distal thoracic limb”
(depends on accuracy of perineural injection)
- Radial, _u_lnar, median, and musculocutaneous nerves
- Requires 2 injection sites, one medial and one lateral
block for declaw
A pre-anesthetic block is indicated for intra- and post-op analgesia
Bupivacaine 1 mg/kg divided between sites, can dilute 1:1 with salin
Peripheral nerve blocks – pelvic limb
Femoral and sciatic nn.
Must be performed together for complete stifle block
Anesthetizes distal to mid-femur
As effective as epidural for stifle surgery
Intercostal n. block
- Anesthesia for thoracotomy, rib fractures, etc.
- Nerves run w/ artery and vein along CAUDAL aspect of rib
- Block at the incision space, and 2 spaces cranial and caudal (5 total)
- Aspirate before injection, avoid thoracic cavity
Intrapleural regional
- Local anesthetic injected into thoracic cavity
- Often delivered through indwelling chest tube post-thoracotomy
- Consider gravity!
- Affected side down for at least 20 mins after injection
- Generally safe and effective
Epidural
- Most commonly performed at the L-S space in small animals
- Requires heavy sedation or anesthesia
- Anesthesia caudal to umbilicus (generally)
Two options:
- Single injection (most common)
- Epidural catheter
Epidural – positioning
- Depends on anesthetist preference and patient condition
Sternal recumbency
- Easier to palpate landmarks
- Legs pulled forward (hips flexed) to maximize L-S space
- Allows hanging drop technique
Lateral recumbency
Epidural injection volume
- Higher volume → more cranial drug spread
- Concern for sympathetic blockade and hypotension with local anesthetic
- Volume 0.2 mL/kg will reach L1
- Sufficient for caudal abdomen, pelvic limbs, perineum
epidural drugs
Most commonly a local anesthetic + opioid
Bupivacaine + morphine
- This combo may provide analgesia for up to 24 hours
Morphine is less lipid soluble than other opioids
- More cranial spread
- Longer duration of action
- Morphine L-S epidural can provide analgesia to thoracic wall and thoracic limbs
epidural complications
Intrathecal (spinal) injection
Use ½ volume if CSF is obtained
Neural damage/toxicity
Use preservative-free, “for epidural use”
Infection
Sterile technique
Hypotension
Fluids and/or vasopressors
epidural opioids complications
Urinary retention
Express bladder post-operatively
Monitor closely for urination before discharge
Pruritis – uncommon
Equine eye
Auriculopalpebral n. block
- Prevents blinking – allows ophthalmic exam
- MOTOR BLOCK ONLY
Supraorbital n. block
- Sensory to middle 2/3 of upper eyelid and palpebral motor
- Used for placement of sub-palpebral lavage catheter (common use)
Retrobulbar block
- transpalpebral most common
- Most commonly used for standing enucleation
Equine epidural anesthesia
- Caudal (not lumbosacral) epidural
- Do not want to lose hind limb motor function
Uses:
- Control of rectal tenesmus
- Correction of uterine torsion, fetotomy, obstetric manipulations
- Tail amputation, rectovaginal fistula repairs, Caslick’s procedure
- Hindlimb procedures and pain (but do not use local anesthetics → motor blockade)
Location:
First coccygeal space
(Co1-Co2)
First movable articulation when tail is raised and lowered
Equine epidural anesthesia – drugs
Local anesthetics:
Remember – these cause motor blockade
Excessive cranial spread to spinal cord segments innervating the pelvic limbs ⇒ hindlimb ataxia or mm. weakness
EXTREMELY DANGEROUS IN A HORSE
Lidocaine 2% 6-8 mL in an adult horse is adequate for anus, perineum, rectum, vulva, vagina, urethra, bladder
Alpha-2 agonists:
Xylazine, detomidine (common)
Causes local analgesia and systemic alpha-2 effects (sedation, 2nd degree AV block, ataxia, etc)
Opioids:
Morphine
- Provides analgesia
- No risk of weakness or motor blockade
- Often administered through epidural catheter for longerterm (days) analgesia
- Hindlimb trauma, surgery, severe laminitis
Side effects: urticaria, ileus
Detomidine + morphine
Common combination
Can provide excellent analgesia for hindlimb pain
Local anesthesia for castration
Commonly used for adjunctive analgesia
Allows lower dose of general anesthetics
~20 mL lidocaine injected into each testicle
Should feel firm after injection
Quickly diffuses into spermatic cord to provide anesthesia
