Locoregional anesthesia in SA

Question 1

What should you do before performing local blocks

Answer 1

Pre block checklist
Right patient
Right sire
Right drug and dose
Equipment
In general: clippers, surgical scrub, sterile gloves, labelled sterile syringes, appropriate size sterile needles
Before injection: aspirate, check for resistance to infection

Question 2

What are teh approx volumes per site in SA local blocks

Answer 2

0.1-0.2ml/kg per site
Remember to stay within safe volume

Question 3

When do you use landmark palpation

Answer 3

Requires palpable anatomical landmarks
Most common
- Dental blocks
- Neuraxial anesthesia
- Ring blocks
Pros: minimal training and equipment needed
Cons:
- 50% success rate (potential for block failures)
- Higher volumes = potential for local anaesthetic toxicity

Question 4

What is nerve simulator guided local blocks

Answer 4

Using peripheral nerve simulator (PNS) in conjunction with palpable landmarks
- Electrical current passing through insulated needle to the tip → depolarizes nerve → visually confirm appropriate motor reflex
Requires specialized insulated needles and PNS system
Objective estimate of needle to needle nerve distance
- Closer to nerve → less electrical current required to elicit motor response
-0.5 mA = motor response within 5 min of nerve (common end point)
- <0.4 mA = potential for intraneural injection

Question 5

What are the pros and cons of nerve stimulator to perform local blocsk

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 locoregional anaesthesia near motor nerve fibers

Question 6

Why would you use an ultrasound guided needle to perform local blocsk

Answer 6

Ultrasound = real time visualisation of nerve and tissue planes for infusion of local anesthetic agent
- Requires specialized echogenic needles (blunt) and ultrasound equipment
Continuing ed
- Anatomy and landmarks
- Understand ultrasound use and images
Uses
- Motor and sensory nerve locoregional anesthesia
- Fascial planes anaesthesia
- Neuraxial anesthesia
Safely track needle advancement
- Limit risk of off target, inadvertent IV or intraneural administration
- Increase accuracy of blockade (90-100%)
Lower volumes of local anaesthetic can be used
- 0.05-0.3 mL/kg

Question 7

What does a retrobulbar block do

Answer 7

Desensitizes globe (cornea and uvea) and conjunctiva and prevents palpebral reflex
Blocks: optic, oculomotor, trochlear, ophthalmic, maxillary and abducens nerves
Use
Enucleation +/- evisceration
Orbectomy

Question 8

What are the complications with a retrobulbar block

Answer 8

Eye penetration, IV or intraneural injection, retrobulbar hemorrhage, proptosis, ocular cardiac reflex, increased intraocular pressure

Question 9

How do you perform a retrobulbar block

Answer 9

Crate bend in 22 gauge 1.5 inch needle
Insert needle at the lateral ⅓ rd boney rim of the lower orbit until it hits bone
Advance the needle along the orbit (scraping sensation can be felt) aiming slightly dorsal/medial
Can feel a slight ‘pop’ when passed through ocular muscle and entering cone
ASPIRATE (very vascular) then inject desired volume of local anesthetic

Question 10

Greater auricular and auriculotemporal block is used for

Answer 10

Desensitizes ear canal and pinna
Does not completely block middle/inner ear
Uses:
Total ear canal ablation +/- bulla ostectomy
Deep ear canal endoscopy or flush

Question 11

What are the side effects for Greater auricular and auriculotemporal block

Answer 11

Common side effects:
Temporary motor paralysis to eyelids
Facial nerve paralysis

Question 12

How do perform a Greater auricular and auriculotemporal block

Answer 12

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

Question 13

What are the uses and complications of the maxillary nerve block

Answer 13

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

Question 14

How do you perform a maxilary nerve block

Answer 14

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

Question 15

What is an infraorbital block used for

Answer 15

Desensitization 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 septum completely)
- Rostral maxillectomy
Caution in cats and brachycephalic dogs: possible ocular trauma

Question 16

How do you perform an intraorbital block

Answer 16

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

Question 17

What are the uses and complications of inferior alveolar nerve block

Answer 17

Desensitizes entire ipsilateral mandible bone and soft tissues, lower lip and lower dental arcade
Complications:
- Tongue desensitization
Uses:
- Dental extractions and mass removals on lower jaw
- Mandibulectomy

Question 18

How do you perfom an inferior alveolar block

Answer 18

Extra-oral approach: (lateral or dorsal recumbency)
- Palpate caudal notch along ventral mandibular bone (before angular process of ramus)
- Pass needle through skin to hit bone of mandible,
- Walk needle tip medially off bone and advance it while scraping along medial aspect of mandible bone, until needle tip reaches mandibular foramen
- Aspirate and inject desired volume of local anesthetic
Intra-oral technique: (lateral or dorsal recumbency)
- Palpate mandibular foramen inside mouth between 3rd molar and angular process of ramus
- Pass needle through gingiva, scraping along mandibular bone until tip is over mandibular foramen
- Aspirate and inject desired volume of local anesthetic

Question 19

What does the mental nerve block freeze and waht are the uses

Answer 19

Desensitization: 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

How do you perform a mental nerve block

Answer 20

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

Question 21

What does a manus block freeze

Answer 21

Desensitizes entire paw/manus
Median, ulnar (palmer and dorsal branches) and radial nerve

Question 22

What are the sues of a manus block

Answer 22

Digit amputation
Wound repairs and mass removals on paw/digits

Question 23

How do you do a manus block

Answer 23

Medial to accessory carpal pad
Lateral and proximal to accessory carpal pad
Dorsal medial carpus

Question 24

What does a RUMM blcok freeze

Answer 24

Desensitizes distal to elbow (carpus, manus, digits)

Question 25

What is a RUMM block used for

Answer 25

Wound/fracture repairs or mass removals to elbow joint

Question 26

What are the 2 techniques of the RUMM block

Answer 26

Distal RUMM block: mid to distal ⅓ humerus - palpation/anatomical +/- nerve stimulator Proximal RUMM block: proximal ⅓ humerus - Ultrasound guided (only one injection) - blocks more cranial

Question 27

How do you do a distal RUMM block

Answer 27

Radial nerve: lateral and caudal aspect of distal ⅓ humerus - Insert needle perpendicular to bone, between long and lateral head triceps until needle encounters humerus - Back needle up slightly, then aspirate and inject desired volume local anaesthetic Ulnar, median, musculocutaneous nerves: medial aspect of distal 1/3rd humerus - Palpate brachial artery and insert needle CAUDAL to artery and biceps brachialis muscle until needle encounters humerus - Back needle up slightly, aspirate and inject ½ of desired volume of local anesthetic - Withdraw needle further while injecting the remaining ½ of local anesthetic

Question 28

What does the brachial plexus block freeze and what are its uses

Answer 28

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

Question 29

What are the complicatiosn with a brachial plexus block

Answer 29

brachial artery perforation, pneumothorax or lung trauma, Horner’s syndrome, diaphragm paralysis (if bilateral)

Question 30

What are the techniques of diong a brachial plexus block

Answer 30

(1) Percutaneous blind injection +/- nerve stimulator (2) Direct visualization and perineural injection (during amputation surgery) (3) Ultrasound guided nerve block Percutaneous (Blind) Technique: Locate acromion, first rib and jugular vein Insert needle along inner side of acromion, aiming ventral and caudal (parallel to jugular vein), trying to scrape along underside of scapula Stop once tip of needle is in line with first rib (caudal margin of scapula) Aspirate and inject ⅓ desired volume local anesthetic Withdraw needle and repeat aspiration and ⅓ injection in middle of scapula and again before needle exits skin (3 total injection spots)

Question 31

What does the pedus block do and what are the uses

Answer 31

Desensitizes entire pedus Blocks tibial nerve, peroneal nerve (branches) and saphenous nerve Uses: Digit amputation wound repair and mass removal or pedus

Question 32

How do you perfom a pedus block

Answer 32

Ring block technique Inject local anesthetic SQ along entire dorsum and ventrum of pedus at level of middle section of metatarsal bones

Question 33

Femoral sciatic nerve freezes what and what are the uses

Answer 33

Desensitizes tissues distal from the caudal ⅓ femur, motor blockade to hindlimb Uses: surgeries below distal 1/3rd femur (TPLO, MPL, fractures, etc.)

Question 34

What are the techniques when performing a femoral sciatic nerve block

Answer 34

Palpation/anatomical +/- nerve stimulator Ultrasound: Saphenous/Sciatic nerve block Less motor blockade, increased ability to use hindlimb while blocking sensory nerves for analgesia Palpation and nerve stimulator technique: Sciatic nerve - Palpate groove between greater trochanter of femur and ischial tuberosity - Insert needle ⅓ distance from greater trochanter on a line with ischial tuberosity - Aspirate and inject desired volume of local anesthetic Femoral nerve - Locate femoral triangle in medial thigh (rectus femoris x sartorius muscle x deep iliopsoas muscle) and palpate femoral artery - Insert needle cranial to artery - Aspirate and inject desired volume of local anesthetic

Question 35

Lumbosacral epidural blocks what

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

Question 36

What are the contraindications of lumbosacral epidural

Answer 36

Bleeding disorders, hypovolemia/hypotension, skin infections, neoplasia at injection site

Question 37

How do you perfom a lumbosacral epidural

Answer 37

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 38

Sacrococcygeal epidural desinsitizes what

Answer 38

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

Question 39

How do you do a Sacrococcygeal epidural

Answer 39

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 40

Intercostal block freezes what and is used when

Answer 40

Desensitizes soft tissues and intercostal spaces distal to injection Uses: Thoracotomy Rib fractures (analgesia) Thoracocentesis

Question 41

What are the complications with an intracoastal block

Answer 41

Intravascular injection Pneumothorax

Question 42

What is the technique when doing a intercostal block

Answer 42

Identify proximal part of rib (close to spine) and caudal aspect Insert needle to hit caudal aspect of chosen rib, walk-off bone until needle slides off back of rib 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 43

Abdominal line block is aand done by

Answer 43

Aka. Incisional block Very simple, provides excellent analgesia at location of incision 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 44

Intraperitoneal block is and done how

Answer 44

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) 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

Transverse abdominis plane (TAP) block is used for

Answer 45

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

How do you do a TAP block

Answer 46

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

Question 47

Intratesticular block is and used for

Answer 47

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

Question 48

How do you do a intratesticular block

Answer 48

Insert needle directly into the testicular body Aspirate and inject until you feel increased ‘pressure’ within testicle or desired volume is reached **can inflate incision line (pre scrotal or scrotal) with small amount or remaining safe volume local anaesthetic**

Question 49

What is a wound soaker catheter

Answer 49

Effective post op analgesia technique Palace 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: 1mg/kg 0.5% every 6-8 hours Lidocaine infusion: 1.5-3mg/kg/hour