Test 3: 35-36: small and large Flashcards
why use local
MAC sparing
LA provide analgesia, so you can use less opioids
can do procedures under sedation instead of general
when not to use LA
neuropathies
skin lesions at injection site
coagulopathies
allergies
altered anatomy
dose dependent complications of LA
- Neurotoxicity
- Cardiotoxicity
- Allergic reaction (PABA: amino-esters, anaphylaxis)
- Methemoglobinemia (prilocaine/benzocaine > lidocaine/procaine)
- Nerve and muscle injury from repeated injections
LA complications due to technique
- Neuronal injury
- Radiculopathy
- Intraneural injection
- Pneumothorax (brachial plexus or thoracic paraverterbral)
- Hemorrhage /Hematomas
topical anesthesia work on —
blocking the free nerve endings of sensory neurons
(applied to skin or mucous membranes)
how does splash block work
local block by applying anesthetic directly into a surgical site or injecting it into a closed space where the agent can diffuse
used for pain surgeries: amputations, ear crops, ablations
infiltration anesthesia works by
deposited around the area to be desensitized by multiple intradermal and/or subcutaneous injections, without regard for the course of the nerves.
can be used to produce linear blocks (linea alba during laparotomies, surgical incisions, biopsies), ring blocks or field blocks.
intratesticular block
injection into center of the testicle (toward the spematic cord)
how does regional or peripheral nerve block work
injection close to nerve to temporarily block sensory and motor functions
need to know where nerve is: anatomical landmarks, electrolocation, ultrasound
how to find the location of a nerve
- anatomic landmarks
- electrolocation- nerve stimulator
- ultrasound
what nerve is blocked in the face
trigeminal (CN5)
opthalmic, maxillary, mandibular branches
why use local for eye and eyelid procedure
- For sensory or motor blockade for ocular exam or surgery of the eye / adnexa
- To decrease volatile anesthetic requirements during ocular procedures
- To decrease possibility of inducing oculocardiacreflex (trigeminovagal)
- To provide postoperative analgesia
what nerves are blocked for ocular procedure
motor: auriculopalpebral nerve (e + f)
sensory: supraorbital (a), Lacrimal nerve(b), Zygomatic nerve (c), Infrathroclear nerve (d)
how to do supraorbital nerve block in horse
Terminal branch of the ophthalmic nerve (CN5)
Sensory to most of the superior lid.
Technique
* Where nerve exits the supraorbital foramen
* Thumb and middle finger are placed at the nasal and temporal canthi
* The index finger will fall on, or near, the supraorbital foramen
* Insert needle into foramen and administer into foramen, during withdrawal, & some SQ
how to do eye block for small animals
nerves all close together, can just go in circle around eye
how to do lacrimal nerve block in large animal
- Branch of the ophthalmic nerve
- Desensitizes the lateral canthus and lateral aspect of the upper eyelid.
Insert the needle at the lateral canthus and infiltrate (3-5 ml) along the dorsal rim of the orbit for the length of the needle.
how to do infratrochlear nerve block in large animal
- Branch of the nasociliary nerve (from the ophthalmic nerve)
*Desensitizes the medial canthus, and the third eyelid
Subcutaneously at the notch in the rim of the orbit just dorsal to the medial canthus (3 – 5 ml LA)
how to do zygomatic nerve block in large animal
- Terminal branch of the maxillary nerve * Desensitizes the lower 2/3rds of the lower eyelid
*Palpated along the edge of the bony orbit ventral to the eye
*LA injected against the bone, insertion of the needle about 1 cm
how to do auriculopalpebral nerve block in large animal
- Terminal branch of the facial nerve (VII).
- Motor to the orbicularis oculi muscle.
- At the dorsal edge of the most dorsal
point of the zygomatic arch (3 – 5 ml LA) - Prevents closure eyelids
- For examination of the eye
- No loss of sensation
how to block globe of the eye
need to block CN 2, motor from CN 3, 4, 6, and sensory from CN 5
can do retrobulbar nerve block
complications of retrobulbar nerve block
- Oculo-cardiac reflex
- Inadvertent globe puncture
- Intravascular injections
- Retrobulbar hemorrhage
- Optic nerve damage
pressing on the eye can cause what reflex
bradycardia and hypotension
(retrobulbar nerve blocks prevent this reflex, but you can cause the reflex while doing the block)
how to do retrobulbar block in SA
- Spinal needle, bent to 20ﹾ
- Insert needle between dorsal aspect of zygomatic process of temporal bone
& orbital ligament, advance caudal-medial-ventral - Aspirate and inject drug (bupivacaine)
- Globe may bulge out slightly
how to do retrobulbar nerve block in Large animal
how to do cornual block in cows
Zygomaticotemporal:
* ½ distance between lateral canthus and lateral aspect of horn
* Advance needle subcutaneously
* 5-10ml anesthetic in fan shape
* Aspirate before injecting
how to do cornual block in goats
Zygomaticotemporal (same as
bovine)
* ½ distance between lateral canthus and lateral aspect of horn
* Advance needle subcutaneously
* 5-10ml anesthetic in fan shape
* Aspirate before injecting
Infrathroclear:
* ½ distance between medial canthus and medial aspect of horn
* Advance needle
* Inject drug in fan shape- subcutaneously
branches of maxillary and mandibular nerve
how to do maxillary nerve block in small animal
inside mouth behind last tooth
how to do maxillary block in large animal
from outside of mouth, draw line from laterl canthus and zygomatic arch
how to do infraorbital nerve block in large animal
Desensitization of the nose, upper incisors and rostral maxilla on the side injected
Draw a line from the rostral end of the facial crest to the nasal incisive notch, the foramen will be just caudal to the midpoint of this line
- Where nerve exits the foramen
- The needle should be directed rostral to caudal and angled to get down to the nerve at the level of the foramen
how to do infraorbital block in small animal
can be done in mouth or outside
infraorbital formamen is above PM3 in dogs, or rostroventral to the medial canthus (Feline)
what is mandibular nerve block used for
This block covers the ipsilateral mandibular quadrant, including teeth, alveolar bone, gingiva
used for
* ipsilateral mandibular dental extractions
* periodontal surgery
* endodontic therapy
* biopsies
* mandibulectomy
how to do large animal mandibular block
The target for injection is the intersection of 2 lines:
1. line that extends caudally along occlusal surface of mandibular cheek teeth
2. line that passes perpendicularly from lateral canthus of the eye
can accidently get lingual nerve- pts can not feel tongue, carful they might bite it
how to do alveolar inferior nerve block in small animals
transcutaneous (extraoral)
trans-buccal (intraoral)
inject medially and caudal to last molar
Palpate the nerve at the opening of the foramen. Using a 25-gauge, 5/8 - 1 inch needle, enter either ventrally through the skin or intraorally through the buccal mucosa, and direct needle toward the mandibular foramen
brachial plexus block are used for
surgery of the thoracic limb from distal 1/3 of humerus (elbow) and distal
how to do brachial plexus block
3 ways:
blind: The needle enters perpendicular to an imaginary line connecting acromion and the greater tuberosity of the humerus, advancing parallel to the body
nerve stimulator
US guided
complications of brachial plexus block
- Vasculature puncture (jugular v., carotid and axillary aa.)
- Pneumothorax / Lung laceration
- Diaphragmatic hemiparalysis (phrenic n. block) (do not block bilaterally, pt will not be able to breathe)
- Horner syndrome (Stellate ganglion block)
how to block radial-ulnar and medial nerve
4 injections
2 palmer: ulnar and median
2 dorsal: radial and ulnar
or you can do ring block- all the way around limb
how to do IVRA
intra-venous regional anesthesia
- used for short surgical procedures involving the distal extremities (distal to the carpus and the hock)
- apply touriquete (90 min max)
- Use IV lidocaine only!
- Bupivacaine can cause severe cardiotoxic effects
risks of intercostal nerve block
- Pneumothorax
- Intrapleural injection
- Vascular puncture
how to do intercostal nerve block
- Enter perpendicular to the respective rib, in the most dorsal aspect
- Redirect the needle toward the caudal aspect of the rib
- Aspirate and check for blood or air
- Inject small volume of local anesthetic
lumbosacral plexus formation
how to do femoral nerve block
medial side of leg
palpate femoral artery and inject just cranial to the artery
used for:
Anesthesia of the femur (mid diaphysis to distal), femorotibial joint (medial aspect of the femorotibial joint capsule), femorotibial intra-articular structures, skin of the dorsomedial tarsus and first digit. Typically used for distal femoral fractures and stifle surgery.
usually will block both femoral and sciatic nerve
complications of femoral nerve block
- Vascular puncture (femoral a. and v.), femoral nerve injury
sciatic nerve block will — and complications
Indications
* In combination with a femoral nerve block, anesthesia of the entire pelvic limb (distal to mid femur) can be
achieved.
* Anesthesia of the stifle (partial) and the structures distal to it.
Complications
* Nerve injury resulting in temporary or permanent foot
knuckling.
how to do sciatic nerve block
parasacral approach: imaginary line between the greater trochanter and the ischiatic tuberosity. Dividing the line in 3rds, enter with the needle perpendicular to skin between the cranial and middle thirds, one thumb dorsally
gluteal approach: US guided
advantages and disadvantages of neuraxial anesthesia
Administration of agents in the CNS, either in the epidural space (extrathecal) or under the arachnoid (intrathecal)
Advantages:
- Perioperative analgesia
- MAC & drug sparing effects
Disadvantages:
- Risk of motor blockage (drug choice)
- Urinary retention (drug choice)
- Risk of drug toxicity, respiratory dysfunction, neurotoxicity, infections
when not to do neuraxial anesthesia
- Coagulopathies
- Hypotensive / Hypovolemic patients (sympathetic blockade)
- Skin infections / neoplasia at the site of injection
- Pre-existing neurological deficits that require monitoring of progression
- Obesity or anatomic abnormalities – difficult landmarks
where is the epidural space
between the periosteum and the dura mater
why use epidural
- Surgery of pelvis and pelvic limbs, tail, perineum
- Rectal / vaginal / preputial prolapse
- Laparotomies/Sternotomies
- Epidural analgesia can also be extended by using an indwelling catheter
how to tell if in epidural space
- Hanging drop
- Loss of resistance (LOR)
- “Pop” feeling is not reliable
- Electrolocation
what kind of meds used for epidural for small animal
how to do epidural in large animal
place epidural catheter
give single, small dose into C1-C2
want to provide pain relief, but allow pt to still stand after procedure
lift tail and find space
what drugs for large animal local epidural
