Locoregional anesthesia in SA Flashcards
What should you do before performing local blocks
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
What are teh approx volumes per site in SA local blocks
0.1-0.2ml/kg per site
Remember to stay within safe volume
When do you use landmark palpation
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
What is nerve simulator guided local blocks
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
What are the pros and cons of nerve stimulator to perform local blocsk
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
Why would you use an ultrasound guided needle to perform local blocsk
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
What does a retrobulbar block do
Desensitizes globe (cornea and uvea) and conjunctiva and prevents palpebral reflex
Blocks: optic, oculomotor, trochlear, ophthalmic, maxillary and abducens nerves
Use
Enucleation +/- evisceration
Orbectomy
What are the complications with a retrobulbar block
Eye penetration, IV or intraneural injection, retrobulbar hemorrhage, proptosis, ocular cardiac reflex, increased intraocular pressure
How do you perform a retrobulbar block
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
Greater auricular and auriculotemporal block is used for
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
What are the side effects for Greater auricular and auriculotemporal block
Common side effects:
Temporary motor paralysis to eyelids
Facial nerve paralysis
How do perform a Greater auricular and auriculotemporal block
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
What are the uses and complications of 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
How do you perform a maxilary nerve block
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
What is an infraorbital block used for
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
How do you perform an intraorbital 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 are the uses and complications of inferior alveolar nerve block
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
How do you perfom an inferior alveolar block
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
What does the mental nerve block freeze and waht are the uses
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
How do you perform a 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 does a manus block freeze
Desensitizes entire paw/manus
Median, ulnar (palmer and dorsal branches) and radial nerve
What are the sues of a manus block
Digit amputation
Wound repairs and mass removals on paw/digits
How do you do a manus block
Medial to accessory carpal pad
Lateral and proximal to accessory carpal pad
Dorsal medial carpus
What does a RUMM blcok freeze
Desensitizes distal to elbow (carpus, manus, digits)
What is a RUMM block used for
Wound/fracture repairs or mass removals to elbow joint
What are the 2 techniques of the RUMM block
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
How do you do a distal RUMM block
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
What does the brachial plexus block freeze and what are its uses
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
What are the complicatiosn with a brachial plexus block
brachial artery perforation, pneumothorax or lung trauma, Horner’s syndrome, diaphragm paralysis (if bilateral)
What are the techniques of diong a brachial plexus block
(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)
What does the pedus block do and what are the uses
Desensitizes entire pedus
Blocks tibial nerve, peroneal nerve (branches) and saphenous nerve
Uses:
Digit amputation
wound repair and mass removal or pedus
How do you perfom a pedus block
Ring block technique
Inject local anesthetic SQ along entire dorsum and ventrum of pedus at level of middle section of metatarsal bones
Femoral sciatic nerve freezes what and what are the uses
Desensitizes tissues distal from the caudal ⅓ femur, motor blockade to hindlimb
Uses: surgeries below distal 1/3rd femur (TPLO, MPL, fractures, etc.)
What are the techniques when performing a 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
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
Lumbosacral epidural blocks what
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
What are the contraindications of lumbosacral epidural
Bleeding disorders, hypovolemia/hypotension, skin infections, neoplasia at injection site
How do you perfom a lumbosacral epidural
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)
Sacrococcygeal epidural desinsitizes what
Desensitizes perineum, tail and sacrum
Pudendal, pelvic and caudal nerves
Great for urinary catheter placement!
How do you do a Sacrococcygeal epidural
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
Intercostal block freezes what and is used when
Desensitizes soft tissues and intercostal spaces distal to injection
Uses:
Thoracotomy
Rib fractures (analgesia)
Thoracocentesis
What are the complications with an intracoastal block
Intravascular injection
Pneumothorax
What is the technique when doing a 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 **
Abdominal line block is aand done by
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
Intraperitoneal block is and done how
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
Transverse abdominis plane (TAP) block is used for
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
How do you do a TAP block
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
Intratesticular block is and used for
Desensitizes spermatic cord and soft tissue structures
Use: castration
Local anesthetic used = lidocaine
How do you do a intratesticular block
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
What is a wound soaker catheter
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
