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