5. Locoregional Anesthesia SA

Question 1

What should we do BEFORE we do a locoregional block?

Answer 1

right patient, site, drug and dose!!!
Required equipment: clippers, surgical scrub, sterile gloves, LABELLED sterile syringes, appropriate size sterile needles
Before injection: Aspirate, check for resistance to injection

Question 2

How can you give a general overview to locoregional anastetic?

Answer 2

know important anatomical structures in area of interest
Always aspirate prior to injection - avoid intravascular local anesthetic injection
Always perform sterile prep of area for injection
Approx. volumes = 0.1-0.2ml/kg per site - stay within safe volume

Question 3

Why is landmark palpation important?

Answer 3

Most common: dental blocks, neuraxial anesthesia, ring blocks
Pros: minimal training and equipment needed
Cons: 50% success rate (potential for block failure)
Higher V = potential for local anesthetic toxicity

Question 4

What is being nerve simulator guided?

Answer 4

using peripheral nerve stimulator (PNS) in conjunction w/ palpebral landmarks - electrical current passing thru insulated needle to the tip > depolarizes nerve > visually confirm appropriate motor reflex
Requires specialized insulated needles and PNS system
Objective estimate of needle-to-nerve distance - closer to nerve > less electrical current required to elicit motor response
0.5mA = motor response within 5mm of nerve (common end point)
<0.4mA = potential for intraneural injection

Question 5

What is the nerve stimulator?

Answer 5

• Pros: improved accuracy over landmark palpation alone
• Approx. 80% success rate for certain blocks
• Need to know specific motor innervation and action obtained from activation of that nerve
• Cons:
• Only for locoregional anesthesia near motor nerve fibres

Question 6

What is ultrasounded guided?

Answer 6

• Ultrasound = real-time visualization of nerve and tissue planes
  for infusion of local anesthetic agent
• Requires specialized echogenic needles (blunt) and ultrasound
  equipment
• Continuing education:
• Anatomy and landmarks
• Understand ultrasound use and images

Question 7

Where might we use ultrasound guided locoregional anesthetic?

Answer 7

• Uses:
• Motor and sensory nerve locoregional anesthesia
  Fascial planes anesthesia
  Neuraxial anesthesia
  Safely track needle advancement
• Limit risks of off-target, inadvertent IV or intraneural
  administration
• Increase accuracy of blockade (90-100%)
• Lower volumes of local anesthetic can be used
• 0.05 – 0.2 mL/kg

Question 8

What is the retrobulbar block?

Answer 8

desensitizes glove (cornea and uvea) and conjunctiva, and prevents palpebral reflex - blocks optic, oculomotor, trochlear, ophthalmic, maxillary and abducens nerves
Complications - eye penetration, IV or intraneural injection, retrobulbar hemorrhage, proptosis, oculo-cardiac reflex, increased intraocular pressure
Used for: enucleation +/- evisceration, orbectomy

Question 9

What is the technique for the retrobulbar block?

Answer 9

1. Create bend in 22-gauge 1.5-inch needle
2. Insert needle at the lateral 1/3rd boney rim of the lower orbit
   until it hits bone
3. Advance the needle along the orbit (scraping sensation can be
   felt) aiming slightly dorsal/medial
4. Can feel a slight ‘pop’ when passed through ocular muscle and
   entering cone
5. ASPIRATE (very vascular) then inject desired volume of local
   anesthetic

Question 10

WHat is the greater auricular and auriculotemporal block?

Answer 10

desensitizes ear canal and pinna - does not completely block middle/inner ear
Common side effects - temp motor paralysis to eyelids, facial nerve paralysis
USed for: total ear canal ablation +/- bulla ostectomy, deep ear canal endoscopy or flush

Question 11

What is the technique for the greater auricular and auriculotemporal block?

Answer 11

• Greater auricular nerve:
  1. Palpate wing of atlas and vertical ear canal (caudal)
  2. Insert needle SQ, directing it rostral/ventral towards TMJ
  3. Aspirate and inject desired volume of local anesthetic
• Auriculotemporal nerve:
  1. Palpate caudal border of zygomatic arch and vertical ear canal
  (rostral)
  2. Insert needle slightly deeper, directing it caudal ventral (towards
  jugular groove)
  3. Aspirate and inject desired volume of local anesthetic

Question 12

What is the maxillary nerve block?

Answer 12

• Desensitizes ipsilateral maxilla bone, intraoral soft
  tissues, upper dental arch, upper lip and nostril, hard
  and soft palate
• Complications:
• Salivary gland or maxillary artery damage
• Nerve damage
• Uses: Maxillectomy, Dental extractions or mass removal or upper jaw
• 2 different techniques for blocking this nerve

Question 13

What is the two techniques for the caudal maxillary block?

Answer 13

• Extra-oral/percutaneous approach:
  1. Insert needle just below ventral border of zygomatic arch,
  2. Advance medially until 0.5cm caudal of the medial canthus of the eye
  3. Aspirate and inject desired volume of local anesthetic
• Intra-oral approach:
  1. Open mouth and retract lips caudally
  2. Insert needle dorsally into the mucosa caudal to the second maxillary molar (do not insert more than 2-4mm to avoid globe perforation)
  3. Aspirate and inject desired volume of local anesthetic

Question 14

What is the infraorbital block?

Answer 14

Desensitizes of maxillary incisors, canines and premolars - rostral branches of maxillary nerve within infra-orbital canal
Uses: dental extractions rostral to 3rd premolar (does not always reach molars)
Rhinoscopy (will not block nasal sepum completely)
Rostral maxillectomy
Caution in cats/brachycephalic dogs: possible ocular trauma

Question 15

What is the technique for the infraorbital block?

Answer 15

1. Palpate infraorbital canal (above 3rd/4th upper premolar) with
   non-dominant hand
2. Keep finger over canal and insert needle through gingiva
   (parallel to soft palate) into canal
3. Aspirate and inject desired volume of local anesthetic
4. Remove needle and apply pressure

Question 16

What is the inferior alveolar nerve block? Whats its more common name?

Answer 16

Mandibular block
desensitizes entire ipsilateral mandible bone and soft tissue, lower lip and lower dental arcade
Complications - tngue desensitization
Used for: dental extractions and mass removals on lower jaw, mandibulectomr

Question 17

What is the extra oral technique for the mandibular block?

Answer 17

Extra-oral approach: (lateral or dorsal recumbency)
1. Palpate caudal notch along ventral mandibular bone
(before angular process of ramus)
2. Pass needle through skin to hit bone of mandible,
3. Walk needle tip medially off bone and advance it while scraping along medial aspect of mandible bone, until needle tip reaches mandibular foramen
4. Aspirate and inject desired volume of local anesthetic

Question 18

What is the intraoral technique for the mandibular block?

Answer 18

1. Palpate mandibular foramen inside mouth between 3rd molar and angular process of ramus
2. Pass needle through gingiva, scraping along mandibular bone
   until tip is over mandibular foramen
3. Aspirate and inject desired volume of local anesthetic

Question 19

What is the mental nerve block?

Answer 19

desensitizes: lower lip, rostral intermandibular region, 2nd, 3rd, 4th premolars - collateral innervation to soft tissues = patchy block
Uses: dental extractions and mass removal rostral to 4th premolar

Question 20

What is the technique for the mental nerve block?

Answer 20

1. Ventral to 2nd mandibular premolar, retract labial frenulum
2. Place needle slightly ventral and caudal to enter foramen
3. Aspirate and inject desired volume of local anesthetic

Question 21

What is the manus block?

Answer 21

Desensitizes entire paw/manus - median, ulnar (palmar and dorsal branches) and radial nerve
Uses: digit amuptation, wound repairs and mass removals on paw/digits

Question 22

What is the three-point block?

Answer 22

the manus block
inject local anesthetic SQ at each site
1. Medial to accessory carpal pad
2. Lateral and proximal to accessory carpal pad
3. Dorsal-medial carpus

Question 23

What is the RUMM block?

Answer 23

desensitizes distal to the elbow (carpus, manus, digits): radial, ulnar, median and musculocutaneous nerves
Uses: wound/fracture repairs or mass removals distal to elbow joint

Question 24

What are the 2 techniques for the rumm block?

Answer 24

2 Techniques: split humerus into 3rd’s
* Distal RUMM block: mid to distal 1/3rd humerus
* Palpation/anatomical +/- nerve stimulator
* Proximal RUMM block: proximal 1/3rd humerus
* Ultrasound guided (only one injection) – blocks more cranial
structures

Question 25

What is the distal RUMM block

Answer 25

Radial nerve: lateral and caudal aspect of distal 1/3rd humerus 1. Insert needle perpendicular to bone, between long and lateral head of triceps until needle encounters humerus 2. Back needle up slightly, then aspirate and inject desired volume local anesthetic Ulnar, median, musculocutaneous nerves: medial aspect of distal 1/3rd humerus 1. Palpate brachial artery and insert needle CAUDAL to artery and biceps brachialis muscle until needle encounters humerus 2. Back needle up slightly, aspirate and inject ½ of desired volume of localanesthetic 3. Withdraw needle further while injecting the remaining ½ of local anesthetic

Question 26

What is the brachial plexus block?

Answer 26

* Desensitizes: tissues below distal humerus * Blocks axillary, radial, ulnar, musculocutaneous and median nerves * Does not always provide consistent desensitization of elbow * Uses: elbow surgery, mass removals, supplemental analgesia for amputation * Complications: brachial artery perforation, pneumothorax or lung trauma, Horner’s syndrome, diaphragm paralysis (if bilateral

Question 27

What are the 3 techniques to the brachial plexus blocks?

Answer 27

* (1) Percutaneous blind injection +/- nerve stimulator * (2) Direct visualization and perineural injection (during amputation surgery) * (3) Ultrasound guided nerve block

Question 28

What is the technique for the percutaneous brachial plexus block?

Answer 28

Percutaneous (Blind) Technique: 1. Locate acromion, first rib and jugular vein 2. Insert needle along inner side of acromion, aiming ventral and caudal (parallel to jugular vein), trying to scrape along underside of scapula 3. Stop once tip of needle is in line with first rib (caudal margin of scapula) 4. Aspirate and inject 1/3rd desired volume local anesthetic 5. Withdraw needle and repeat aspiration and 1/3rd injection in middle of scapula and again before needle exits skin (3 total injection spots)

Question 29

What is the pedus block?

Answer 29

desensitizes entire pedus - blocks tibial nerve, peroneal nerve (branches) and saphenous nerve Uses: digit amputation, wound repair and mass removal or pedus

Question 30

What is the ring block technique?

Answer 30

Pedus Block * Desensitizes entire pedus * Blocks tibial nerve, peroneal nerve (branches) and saphenous nerve * Uses: * Digit amputation * wound repair and mass removal or pedus * Ring block technique: * Inject local anesthetic SQ along entire dorsum and ventrum of pedus at level of middle section of metatarsal bones

Question 31

What is the femoral sciatic nerve block?

Answer 31

* Desensitizes tissues distal from the caudal 1/3rd femur, motor blockade to hindlimb * Uses: surgeries below distal 1/3rd femur (TPLO, MPL, fractures, etc.

Question 32

What are the two techniques for femoral sciatic nerve block?

Answer 32

* Palpation/anatomical +/- nerve stimulator * Ultrasound: Saphenous/Sciatic nerve block * Less motor blockade, increased ability to use hindlimb while blocking sensory nerves for analgesia

Question 33

What is the technique for palpating and using the nerve stimulator for the femoral nerve block?

Answer 33

* Femoral nerve: 1. Locate femoral triangle in medial thigh (rectus femoris x sartorius muscle x deep iliopsoas muscle) and palpate femoral artery 2. Insert needle cranial to artery 3. Aspirate and inject desired volume of local anesthetic

Question 34

What is the technique for palpating and using the nerve stimulator for the sciatic nerve block?

Answer 34

* Sciatic nerve: 1. Palpate groove between greater trochanter of femur and ischial tuberosity 2. Insert needle 1/3rd distance from greater trochanter on a line with ischial tuberosity 3. Aspirate and inject desired volume of local anesthetic

Question 35

What is the lumbosacral epidural?

Answer 35

* Desensitizes all structures caudal to injection site * Used for procedures involving abdomen, pelvis, pelvic limbs, perineum, and tail * Cranial extent = depends on VOLUME * 1mL/ 5 kg (0.2 mL/kg) = T13 * MAXIMUM = 6-7 mL total * Injection site = L7 – S1 * Performed ASEPTICALLY with special spinal/epidural needles * Contraindications: * Bleeding disorders, hypovolemia/hypotension, skin infections, neoplasia at injection site

Question 36

What is the lumbosacral epidural technique?

Answer 36

* Place patient in sternal (easiest) or lateral recumbency, and pull hindlimbs forward * Palpate wings of ilium with thumb and middle finger, let pointer finger fall on midline (spine) – forms a triangle! * Identify largest vertebral space with pointer finger * Angle needle 45o, insert needle into space between vertebrae slowly until you feel approx. 3 ‘pops’ * Pops = SQ, interspinous ligament and interarcuate ligament * Tests to ID proper epidural placement: * Hanging drop (sterile saline), loss of resistance (special syringe vs saline with air bubble), or aspirate (no blood or CSF)

Question 37

WHat is the sacrococcygeal epidural block?

Answer 37

* Desensitizes perineum, tail and sacrum * Pudendal, pelvic and caudal nerves * Great for urinary catheter placement!

Question 38

What is the technique for the sacrococcygeal epidural block?

Answer 38

* Similar to lumbosacral epidural block, but more caudal and uses lower volume (0.1 mL/kg or 1mL/ 7-10 kg) * Palpate spine at tail base and ID most movable joint when tail is moved up/down (S3 – Co1 or Co1 – Co2) * Perform aseptically, similar to epidural technique

Question 39

What is the intercostal block?

Answer 39

Desensitizes soft tissues and intercostal spaces distal to injection Uses: thoracotomy, rib fractures (analgesia), thoracocentesis complications: intravascular injection, pneumothorax

Question 40

What is the technique for intercostal block?

Answer 40

1. Identify proximal part of rib (close to spine) and caudal aspect 2. Insert needle to hit caudal aspect of chosen rib, walk-off bone until needle slides off back of rib 3. ASPIRATE (no blood or air) and inject 0.5 – 2mL/site depending on patient size (remember to stay within SAFE DOSE) ** Need to block 2-3 spaces cranial and caudal to target rib to get full coverage **

Question 41

What is the abdominal line block?

Answer 41

incisional block or splash block provides excellent analgesia at location of incision

Question 42

What is the technique for abdominal line block?

Answer 42

Technique: Inject local anesthetic subcutaneously at expected incision site * Can be done post-operatively by splashing area with local anesthetic solution prior to closure or injecting subcutaneously after closure

Question 43

What is the intraperitioneal block?

Answer 43

* Intraperitoneal lavage: desensitizes serosal surfaces of abdominal cavity * Mostly used to desensitize ovarian tissues for spay * Can dilute safe volume of local anesthetic with saline for larger volume (0.4-0.6 mL/kg

Question 44

What is the technique for intraperitoneal block?

Answer 44

Technique: instill mixture in abdomen once peritoneum is open or directly around ovarian pedicles once visualized, or at the end of the procedure prior to abdominal closure * Can use remainder of safe volume for incisional block

Question 45

What is the transverse abdominis plane block?

Answer 45

TAP block * Abdominal wall = 3 muscle layers (external oblique, internal oblique, transverse abdominis muscles) * Transversus abdominis fascial plane = between obliques and transverse abdominis muscle * Carries nerves that supply sensation to abdominal wall soft tissues

Question 46

What is the technique for the transverse abdominis plane block?

Answer 46

Technique = ultrasound guided block 1. Identify muscle layers of abdominal wall, insert needle and advance until reaching fascial plane between internal oblique and transverse abdominis 2. Aspirate and inject local anesthetic to bathe nerves in this area 3. Repeat these steps in 4-6 sites total along abdominal wall

Question 47

What is the intratesticular block?

Answer 47

* Desensitizes spermatic cord and soft tissue structures * Use: castration * Local anesthetic used = lidocaine

Question 48

What is the intratesticular block technique?

Answer 48

Technique: 1. Insert needle directly into testicular body 2. Aspirate and 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 remaining safe volume local anesthetic **

Question 49

What is a wound soaker catheter?

Answer 49

* Effective post-operative analgesia technique * Place flexible large-bore rubber catheter (home-made or commercial) inside incision at the end of major surgery * Uses = amputations, total ear canal ablation, oncologic surgery, large wounds * Bupivacaine boluses: 1 mg/kg 0.5% every 6-8 hours * Lidocaine infusion: 1.5-3 mg/kg/hour