6. Locoregional Anesthesia LA Flashcards
What is a general overview of locoregional anesiasia for LA?
- Need to know important anatomical structures in area of interest
- Always aspirate prior to injection
- Avoid intravascular local anesthetic injection
- Always perform sterile preparation of area for injection
- Approx. volumes for adult cattle/equine nerve blocks = 5-15 mL per site
- Most common local anesthetic used = lidocaine
- Sheep/Goats/Camelids = 4-5 mg/kg
- Horses = 8 mg/kg
- Cattle = 8 mg/kg
What is the cornual nerve block?
- Desensitizes horn
- Blocks ophthalmic branch of trigeminal nerve: cornual nerve, +/-
supraorbital and infratrochlear nerves - Uses: Dehorning or horn injury repair
What is the technique for the cornual nerve block?
- Young cattle: palpate upper 1/3rd temporal ridge approx. 2-5 cm down
from horn based – insert needle SQ, aspirate and inject 3-5 mL local
anesthetic - Adult cattle (well-developed horns) = ring block around entire base of
horn or three-point block to completely desensitize horn
What is the technique for a cornural nerve block for a goat?
- Goats: TWO branches of cornual nerve
- Must block BOTH to completely desensitize the horn
Technique: insert needle SQ at each site, aspirate and inject 2-3 mL
lidocaine per site - Zygomaticotemporal (aka. lacrimal) branch: behind root of supraorbital
process, halfway between lateral canthus of eye and lateral base of horn - Infratrochlear branch: dorsomedial margin of orbit, midway between
medial base of horn and medial canthus of the eye
What is the large animal opthalmic block?
- Sensory denervation of eyelid = must block 4 separate
nerves - Upper eyelid: Supraorbital (frontal), lacrimal nerves
- Lower eyelid: zygomatic, infratrochlear nerves
- Motor innervation to eyelid:
- Palpebral nerve (branch of auriculopalpebral nerve) = must
block to prevent blinkin
What is the technique for the LA ophthalmic upper lid blocks?
Technique for Upper eyelid
* Insert needle SQ at each site, aspirate and inject desired
volume of local anesthetic
1. Supraorbital nerve: Dorsal to medial canthus of eye,
medial to supraorbital ridge
* Also Blocks part of palpebral nerve
2. Lacrimal nerve: Palpate lateral canthus and place needle
pointing medial along dorsal orbit rim
What is the technique for the LA ophthalmic lower eyelid blocks?
- Infratrochlear nerve: dorsal orbital rim near medial
canthus (bony notch) - Zygomatic nerve: lateral aspect of lower orbit rim
and supraorbital part of zygomatic arch (direct
ventral)
What is the LA retrobulbar block?
- Retrobulbar block: desensitizes ocular surface, globe
and intraocular structures - Optic, oculomotor, trochlear, maxillary and abducens nerves
- Surgical preparation should be done with iodine 1.25% solution and sterile eye wash
- Complications:
- Eye penetration, IV or intraneural injection, retrobulbar hemorrhage, proptosis, oculo-cardiac reflex, increased IOP, chemosis
- Use: enucleation +/- evisceration, orbectomy
What is the technique for the retrobulbar block for cattle?
- Bend 20-gauge, 9-cm needle into circular angle
- Insert needle at 4 points around orbit (12, 3, 6, and 9 o’clock positions) and advance through soft tissues until bone of orbit is hit
- Advance needle along orbit bone until needle is located behind the orbit (feel ‘pop’ sensation when entering retrobulbar cone)
- Aspirate, then inject 5mL lidocaine per site (20 mL total)
What is the technique for the retrobulbar block for the horse?
- Palpate orbital fossa just caudal to posterior aspect of dorsal orbital rim
- Insert 22-gauge, 3.5-inch spinal needle perpendicular to skin, advance until eye rolls dorsally in orbit and a ‘pop’ is felt (entering retrobulbar cone)
- Insert needle 2-3mm more, aspirate then inject 10mL
lidocaine or bupivacaine
What is the maxillary nerve block?
- Desensitizes maxilla bone, intraoral soft tissues, upper dental arch, upper lip and nostril, hard and soft palate
- Uses: Extraction of maxillary teeth, maxillary sinus trephination, nasal
cavity surgery - Complications: salivary gland or maxillary artery damage, nerve damage
What is the technique for the maxillary nerve block?
- Palpate infraorbital foramen
- Insert needle approx. 3-4 cm into foramen
- Aspirate then inject approx. 5mL local anesthetic
What is the inferior alveolar nerve block?
Mandibular block
* Desensitizes entire ipsilateral mandible bone and soft tissues,
lower lip and lower dental arcade
* Complications: tongue desensitization
* Uses: dental extractions for molars/premolars,
mandibulectomies, mandibular fracture repairs, mass
removals, etc
What is the extraoral mandibular block technique?
- Estimate mandibular foramen location by imagining
two intersecting lines: vertically down from caudal aspect of orbit AND horizontal line parallel to
occlusal surface of lower cheek teeth - Insert 18 gauge, 8 – 10-inch spinal needle along caudal mandible until you hit the bone
- Walk off the end of the mandible heading medially, insert needle by scraping along inner aspect of mandible until you reach intersection of lines previously discussed
- Aspirate, then inject desired volume of local anesthetic
What is the intraoral technique for the mandibular block?
- Attach 20-gauge, 1.5-inch needle (bent 20-30
degrees) to IV fluid extension set, and guide insertion
into oral cavity with 12-inch pliers - Insert needle into mucosa just caudal and above
occlusal surface of 3rd mandibular molar (lateral to
palate) - Aspirate and inject desired volume of local anesthetic
What is the mental nerve block?
- Lower lip desensitization only (A)
- Local anesthetic injected around mental foramen
- Lower incisors to 3rd premolar desensitization =
mandibular alveolar nerve block (B) - Insert needle into mental foramen and advance into
mandibular canal (ventromedial direction)
What is purpose of the distal limb locoregional anesthesia?
- Purpose: specific nerve blocks used to
diagnose lameness but also to provide analgesia
to lower limb for surgical procedures
What is the digital nerve block and technique?
Distal Limb Locoregional Anesthesia
* Purpose: specific nerve blocks used to
diagnose lameness but also to provide analgesia
to lower limb for surgical procedures
What is the abaxial sesamoidean nerve block and technique?
- Desensitizes medial and lateral palmar (plantar) nerves
- Palpate nerves as they pass proximal sesamoids
- Blocks entire foot, back pastern and distal sesamoidean ligaments
- Can result in partial numbing of fetlock
What is the low palmar/plantar nerve block? and technique?
- Desensitizes: structures distal to fetlock and fetlock joint
- Does not block small area dorsal to fetlock joint
- Approach: 4-point block (patient should be bearing weight on the limb of choice)
- Medial and lateral palmar (plantar) nerves: between flexor tendon and suspensory ligament
- Medial and lateral palmar (plantar) metacarpal nerves: between suspensory ligament and splint
bone
What is the high plantar/palmar nerve block and technique?
- Desensitizes palmar metacarpal (metatarsal) region and all digits distal to fetlock
- Does not block dorsal fetlock metacarpal (metatarsal) region
- Approach: level of the proximal quarter of metacarpus (metatarsus)
proximal to communicating branch of medial and lateral palmar
(plantar) nerves - Limb can be elevated or weight bearing
- Needle (perpendicular to skin): 4.5 cm distal to carpometacarpal joint into groove between suspensory ligament and deep flexor tendon
- Medial and lateral sides
What is the proximal forelimb block and techniques?
- Desensitizes 3 nerves: median, ulnar, and musculocutaneous
nerves
Proximal Forelimb Block
Technique: - Median nerve: medial aspect forelimb, 5 cm ventral to elbow
- Needle inserted between border of radius and internal flexor carpi radialis muscle belly, deep
to superficial pectoral muscle - Ulnar nerve: 10cm proximal to accessory carpal bone between flexor carpi ulnaris and ulnaris lateralis muscles
- Medial cutaneous antebrachial nerve (branch of musculocutaneous) Anteriomedial
aspect of forelimb - Halfway between elbow and carpus, palpate cranial to cephalic vein
What is the proximal hindlimb block
- Desensitizes: tibial, saphenous, superficial peroneal
(superficial fibular), deep peroneal (deep fibular) nerves
What is the tibial nerve technique?
- Tibial nerve: medial aspect of limb, 10 cm proximal to point of tarsus
- Between combined gastrocnemius muscle tendons and superficial digital flexor tendon
- Desensitizes posterior metatarsal area, foot except anterolateral region
What is the saphenous nerve technique?
- Saphenous nerve: medial aspect of limb, proximal to tibiotarsal joint
- Can have two nerve trunks: caudal AND cranial aspect of medial saphenous vein → inject on
either side of vein - Desensitizes medial aspect of thigh and part of metatarsal region
What is the superficial and deep peroneal nerve block technique?
- Superficial and deep peroneal nerves: 10cm proximal to
lateral malleolous of tibia - Between long and lateral digital extensor muscles
- Deposit local anesthetic SQ around superficial nerve branch
- Advance 2-3 cm (enter deep fascia) and deposit local anesthetic
around deep branch - Desensitizes anteriolateral tarsal and metatarsal regions and
tarsus joint capsule
What is a caudal epidural block?
Site = S5 – Co1 or Co1 – Co2
* First midline depression caudal to sacrum palpated when tail is
moved up and down
* Prepare area aseptically, as in small animal epidural procedures
* Volume = DIFFERENT FROM SMALL ANIMALS
* 6-8 mL total (450 kg horse) = perineum, rectum, vulva vagina,
urethra and bladder
* 10 mL MAXIMUM for standing procedures
* Complications: ataxia, motor paralysis to hindlimbs,
excitement, infection, hypotension
What is the caudal epidural block technique?
- Prep area and instill 1-2 mL lidocaine in soft tissues where you will place epidural needle
- Insert needle at 30o angle to skin, fill hub with sterile saline
- Advance needle through tissues until epidural space is entered = sub- atmospheric pressure sucks in drop of saline
- Attach syringe with epidural solution and inject slowly – there should be NO resistance
What is the inverted L block?
- Similar to simple line block, except injecting local
anesthetic in TWO long lines
1. Behind the last rib (R13)
2. Below transverse process of vertebrae (L1 – L5) - Total volume = up to 100mL lidocaine (adult cow)
evenly distributed - Blocks skin but not peritoneum
- Advantage over line block: no anesthetic agent in
incision line (minimized edema, hematoma and
healing interference)
What is the proximal paravertebral block?
- Block T13, L1, L2 nerves exiting intervertebral foramen
near dorsal aspect of transverse process - Desensitizes skin, muscle and peritoneum
- Animal will bend towards the opposite side (scoliosis) and
flank will be warm (vasodilatation) - Standing laparotomy procedures: C-section, rumenotomy, cecotomy, intestinal obstruction,
displaced abomasum, volvulus, etc. - Use 10-20 mL lidocaine per site (onset 10 min, duration of block 90 min)
- Complications: aorta puncture, vena cava puncture, ataxia and loss of hindlimb motor
function
What is the technique for the proximal paravertebral block?
- Prep skin overlying area T12 – L3 transverse processes
- 2.5-5 cm from midline, along cranial aspect of transverse spinal process
- Inject 2-3 mL lidocaine under skin along cranial border for local anesthesia in order to perform needle insertion
- Insert 16 - 18-gauge 1.5 – 6-inch needle until you hit cranial aspect of
transverse process bone, walk off cranially until you pop through intertransverse
ligament - Aspirate, inject 10-15mL lidocaine, withdraw needle 1-3 cm and repeat by injecting 5mL lidocaine above intertransverse ligament
- Repeat steps at L1 and L2 transverse processes
Sheep/goats = only use 2-3 mL lidocaine per site!
What is the distal paravertebral block?
- Desensitizes T13, L1, L2 but in more distal position
(ends of L1, L2 and L4) - Used for similar reasons as proximal block
- Advantages over proximal blocks:
- Minimal risk of penetrating vascular structures
- Not as much scoliosis
- Minimal risk of ataxia and pelvic limb paralysis
- Disadvantages:
- Large volume required
- Variable efficacy for skin desensitization
What is the technique for distal paravertebral block?
- Prepare and desensitize skin similar to proximal
paravertebral block but at L1 – L4 - Insert 18-gauge, 1.5-inch needle until you hit the lateral aspect of L1 transverse process
- Walk needle ABOVE transverse process, aspirate and inject in fan infiltration pattern 15 mL
lidocaine - Back needle up until you hit the lateral aspect of the transverse process again
- Walk needle BELOW transverse process, aspirate and inject in fan pattern 5 mL lidocaine
Sheep/goats = only use 2-3 mL lidocaine per site!
What is the intratesticular block and technique?
- Desensitizes spermatic cord and soft tissue structures
- Used for castration
- Local anesthetic used = lidocaine
Technique:
1. Insert needle directly into testicular body and aspirate
2. Inject until you feel increased ‘pressure’ within testicle or desired volume is reached
** Can infiltrate incision line (pre-scrotal or scrotal) with small amount of local anesthetic *
What is the teat locoregional anesthesia
Dairy cattle, sheep and goats for surgical procedures of the teat
What is the inverted V block technique for the teat locoregional anesthesia
Inverted V Block: 25-gauge, 1.5-cm needle inserted into
skin and musculature dorsal to surgical site in inverted V patter.
Aspirate and inject 2.5 mL local anesthetic in each site
What is the ring block technique for the teat locoregional anesthesia
25-gauge, 1.5-cm needle inserted into skin and
muscle encircling entire base of teat and injecting 5mL total
equally around entire teat
What is the Teat cistern infusion technique for the teat locoregional anesthesia
Teat Cistern Infusion: milk out cistern then place tourniquet on
teat base (prevent local anesthetic from entering udder). Sterile teat
cannula inserted into teat cistern and inject 10mL local anesthetic.
Remove cannula and milk out any extra local anesthetic.
* At end of procedure, remove tourniquet
What is intravenous regional anesthesia? Whats its other name?
Bier’s block
* Tourniquet applied to limb proximal to planned surgical area, lidocaine injected IV distal to
tourniquet
* Local anesthetic spread from vessels to nearby nerves and tissues
* Time and area dependent: short
procedures (< 90 minutes) on distal
extremities (distal to elbow or hock)
* Alternative to ring block, minimal blood loss
* Potential for tissue necrosis and ischemic pain
What is the technique for the intravenous regional anesthesia?
- Place loose tourniquet on limb and ID palpable arterial pulse in area of interest
- Insert IV catheter in distal vein, then exsanguinate distal limb using flexible bandage
- Inflate/tighten tourniquet > 50-100 mmHg higher than SAP – document time! (Complete
procedure within 90 min form this time) - Remove bandage used to exsanguinate the limb
- CHECK for PULSE
- Inject 20 mL lidocaine IV slowly (2-3 min) – document time!**
- At end of procedure, slowly remove tourniquet while surgical site is closed
** Sheep/goats = only use 3-4 mL lidocaine!
