Locoregional anesthesia in LA Flashcards
What are the common local anesthetic volumes used in LA
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 does a corneal nerve block freeze LA
Dessnitizes horn
Blocks ophthalmic branch of trigeminal nerve: cornual nerve, +/- supraorbital and infratrochlear nerves
Uses: dehorning or horn injury repair
How do you do a cornual nerved block LA
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
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
How do you freeze a LA eye
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 blinking
What is the technique to freezing the upper eyelid in LA
Insert needle SQ at each site, aspirate and inject desired volume of local anesthetic
Supraorbital nerve: Dorsal to medial canthus of eye, medial to supraorbital ridge
Also Blocks part of palpebral nerve
Lacrimal nerve: Palpate lateral canthus and place needle pointing medial along dorsal orbit rim
What is the technique to freezing the lower eyelid in LA
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)
Auriculopalpebral block is used for what in LA
Prevents blinking during surgery or ocular exams
Sensation to the eye is STILL PRESENT
must block all sensation to eye with 4-point blocks previously discussed
how do you perform a Auriculopalpebral block LA
Two Techniques: insert needle SQ, aspirate and inject desired volume of local anesthetic and each site
A: depression caudal to mandible at ventral edge of temporal part of zygomatic arch
B: most dorsal point of zygomatic arch
Retrobulbular block is used for what in LA
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
What are the uses and complications of retrobulbular blocks LA
Complications: Eye penetration, IV or intraneural injection, retrobulbar hemorrhage, proptosis, oculo-cardiac reflex, increased IOP, chemosis
Use: enucleation +/- evisceration, orbectomy
How do you perform a retrobulbular block in 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)
How do you perform a retrobulbular block in 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 2-3 mm more, aspirate then inject 10mL lidocaine or bupivacaine
Maxillary nerve block freezes what and is used for in LA
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
What are the complications of maxillary nerve blocks in LA
Complications: salivary gland or maxillary artery damage, nerve damage
How do you perform a maxillary nerve block in LA
Palpate infraorbital foramen
Insert needle approx. 3-4 cm into foramen
Aspirate then inject approx. 5mL local anesthetic
Inferior alveolar nerve block (aka mandibular block) freezes what is used when and complications in LA
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.
How do you do a inferior alveloar nerve block in LA
Extra-Oral Technique: (most common)
- 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
Intra-Oral Technique:
- 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 does a mental nerve block freeze in LA and how do you do it
Lower lip desensitisation only
Local anesthetic injected around mental foramen
Lower incisors to 3rd premolar desensitization = mandibular alveolar nerve block
Insert needle into mental foramen and advance into mandibular canal (ventromedial direction)
What is the purpose of Distal limb locoregional anaesthesia in LA
Purpose: specific nerve blocks used to diagnose lameness but also to provide analgesia to lower limb for surgical procedures
What does a digital nerve block do LA
Palmer (planter) nerves: dorsal to fetlock at sesamoids
Three nerves: anterior, middle and palmar/plantar digital nerves
Sensory to hoof, navicular bone and bursa, corium, frog, sole
How do you perfom a digital nerve block in LA
Palpate nerve running along palmar/plantar aspect of pastern (medially or laterally by vein/artery) → passes distally over flexor tendon
Place needle midway b/w coronary band and fetlock
Desensitizes posterior ⅓ foot
Abaxial (basilar) sesamoidean nerve block does what and how to preform LA
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
Low palmer (planter) nerve block desnesitizes what LA
structures distal to fetlock and fetlock joint
Does not block small area dorsal to fetlock joint
How do you do a low palmer/planter nerve block in LA
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
High palmar/plantar nerve block desinsitizes what LA
Desensitizes palmar metacarpal (metatarsal) region and all digits distal to fetlock
Does not block dorsal fetlock metacarpal (metatarsal) region
how do you do a High palmar/plantar nerve block LA
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
Proximal forelimb block desnesitizes what LA
3 nerves: median, ulnar, and musculocutaneous nerves
How do you do a proximal forelimb block LA
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
Proximal hindlimb block Desensitizes what LA
Desensitizes: tibial, saphenous, superficial peroneal (superficial fibular), deep peroneal (deep fibular) nerves
How do you do a proximal hindlimb block LA
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
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
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
Where do you perform a caudal epidural in a LA
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
How much do you give for a caudal epidural in LA
6-8 mL total (450 kg horse) = perineum, rectum, vulva vagina, urethra and bladder
10 mL MAXIMUM for standing procedures
What are the caudal epirual complicatiosn in LA
Complications: ataxia, motor paralysis to hindlimbs, excitement, infection, hypotension
How do you do a caudal epidural in a LA
Prep area and instill 1-2 mL lidocaine in soft tissues where you will place epidural needle
Insert needle at 30 degree 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
How do you do an inverted Lblock in LA
Similar to simple line block, except injecting local anesthetic in TWO long lines
Behind the last rib (R13)
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 does a Proximal paravertebral block freeze in LA
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)
Why woudl you do a Proximal paravertebral block in LA
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)
What are the complications of Proximal paravertebral block in LA
Complications: aorta puncture, vena cava puncture, ataxia and loss of hindlimb motor function
How do you do a proximal paravertebral block in LA
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
Sheep/goats= only use 2-3 mL lidocaine per site!
Repeat steps at L1 and L2 transverse processes
Distal paravertebral block freezes what and used for in LA
Desensitizes T13, L1, L2 but in more distal position (ends of L1, L2 and L4)
Used for similar reasons as proximal block
Advantages of a distal paravertebral block over proximal LA
Minimal risk of penetrating vascular structures
Not as much scoliosis
Minimal risk of ataxia and pelvic limb paralysis
Disadvantages of a distal paravertebral block over proximal LA
Large volume required
Variable efficacy for skin desensitization
How do you do a distal paravertebral block in LA
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
Sheep and goats = only use 2-3 ml lidocaine per site
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
Intratesticular block for LA and technique
Desensitizes spermatic cord and soft tissue structures
Used for castration
Local anesthetic used = lidocaine
Technique:
- Insert needle directly into testicular body and aspirate
- 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 **
Teat locoregional anaesthesia is used in
Dairy cattle, sheep and goats for surgical procedures of the teat
how do you perform local blocks in LA teats
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
Ring Block: 25-gauge, 1.5-cm needle inserted into skin and muscle encircling entire base of teat and injecting 5mL total equally around entire teat
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
IV regional anaesthesia is and used for in LA
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
How do you do a IV regional block in LA
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!
Sheep/goats = only 3-4 ml lidocaine
At end of procedure, slowly remove tourniquet while surgical site is closed
