5. Locoregional Anesthesia SA Flashcards
What should we do BEFORE we do a locoregional block?
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
How can you give a general overview to locoregional anastetic?
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
Why is landmark palpation important?
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
What is being nerve simulator guided?
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
What is the nerve stimulator?
- 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
What is ultrasounded guided?
- 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
Where might we use ultrasound guided locoregional anesthetic?
- 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
What is the retrobulbar block?
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
What is the technique for the retrobulbar block?
- Create bend in 22-gauge 1.5-inch needle
- Insert needle at the lateral 1/3rd 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
WHat is the greater auricular and auriculotemporal block?
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
What is the technique for the greater auricular and auriculotemporal block?
- 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
What is the maxillary nerve block?
- 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
What is the two techniques for the caudal maxillary block?
- 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
What is the infraorbital block?
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
What is the technique for the infraorbital block?
- 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
What is the inferior alveolar nerve block? Whats its more common name?
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
What is the extra oral technique for the mandibular block?
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
What is the intraoral technique for the mandibular block?
- 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
What is the mental nerve block?
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
What is the technique for the mental nerve block?
- 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
What is the manus block?
Desensitizes entire paw/manus - median, ulnar (palmar and dorsal branches) and radial nerve
Uses: digit amuptation, wound repairs and mass removals on paw/digits
What is the three-point block?
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
What is the RUMM block?
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
What are the 2 techniques for the rumm block?
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
What is the distal RUMM block
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
What is the brachial plexus block?
- 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
What are the 3 techniques to the brachial plexus blocks?
- (1) Percutaneous blind injection +/- nerve stimulator
- (2) Direct visualization and perineural injection (during amputation surgery)
- (3) Ultrasound guided nerve block
What is the technique for the percutaneous brachial plexus block?
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)
What is the pedus block?
desensitizes entire pedus - blocks tibial nerve, peroneal nerve (branches) and saphenous nerve
Uses: digit amputation, wound repair and mass removal or pedus
What is the ring block technique?
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
What is the femoral sciatic nerve block?
- Desensitizes tissues distal from the caudal 1/3rd femur, motor
blockade to hindlimb - Uses: surgeries below distal 1/3rd femur (TPLO, MPL, fractures, etc.
What are the two techniques for femoral sciatic nerve block?
- Palpation/anatomical +/- nerve stimulator
- Ultrasound: Saphenous/Sciatic nerve block
- Less motor blockade, increased ability to use hindlimb while
blocking sensory nerves for analgesia
What is the technique for palpating and using the nerve stimulator for the femoral nerve block?
- 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
What is the technique for palpating and using the nerve stimulator for the sciatic nerve block?
- 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
What is the lumbosacral epidural?
- 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
What is the lumbosacral epidural technique?
- 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)
WHat is the sacrococcygeal epidural block?
- Desensitizes perineum, tail and sacrum
- Pudendal, pelvic and caudal nerves
- Great for urinary catheter placement!
What is the technique for the sacrococcygeal epidural block?
- 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
What is the intercostal block?
Desensitizes soft tissues and intercostal spaces distal to injection
Uses: thoracotomy, rib fractures (analgesia), thoracocentesis
complications: intravascular injection, pneumothorax
What is the technique for intercostal block?
- 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 **
What is the abdominal line block?
incisional block or splash block
provides excellent analgesia at location of incision
What is the technique for abdominal line block?
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
What is the intraperitioneal block?
- 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
What is the technique for intraperitoneal block?
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
What is the transverse abdominis plane block?
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
What is the technique for the transverse abdominis plane block?
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
What is the intratesticular block?
- Desensitizes spermatic cord and soft tissue structures
- Use: castration
- Local anesthetic used = lidocaine
What is the intratesticular block technique?
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 **
What is a wound soaker catheter?
- 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
