Locoregional Nerve Blocks- Small Animal Flashcards
What are the four methods of local anesthesia?
- Topical
- SubQ
- Line blocks
- Wound soaker catheter
What are two types of topical anesthesia administration?
- EMLA cream- lidocaine + prilocaine)
2. Lidoderm- 5% lidocaine patches
Do lidoderm patches provide a complete block?
No- only analgesic effects
What drugs are used for opthalmic analgesia?
Tetracaine or proparacaine
What drug is used for laryngeal anesthesia?
2% lidocaine- usually for intubation
What is SQ local anesthesia used for?
Wounds, masses, or biopsy
T/F: Ventral midline blocks have conflicting evidence for actually decreasing pain.
True
What is a wound soaker catheter?
A long fenestrated closed tip catheter that is placed during surgery deeply close to visualized nerves
What are wound soaker catheters used for?
- Total ear canal ablation
- Amputation
- Oncology surgery
- Large wound closure
What are complications associated with wound soaker catheters?
- Catheter dislodgement or disconnection
- Local anesthetic toxicity
- Delayed wound healing
What are some advantages to wound soaker catheters?
- Technically simple
- Consistent and prolonged analgesia
- Decreased need for systemic analgesics
What are the indications for a bier block?
Distal extremity procedures
What are some advantages of a bier block?
- Simple and reliable
2. Minimal blood loss and clear field
What is the procedure for a bier block?
- Place distal IVC
- Exsanguinate limb (elevate or tight wrapping)
- Place tourniquet proximally
- Remove bandage
- Inject lidocaine and allow to sit
- Remove catheters and tourniquet
What are some IVRA complications?
- Pain
- Ischemia/nerve injury
- Limb swelling
- Hematoma
- Local anesthetic toxicity
What are indications for a retrobulbar block?
- Enucleation
- Eviscceration/prosthesis
- Intraocular surgery
What nerves are effected in a retrobulbar block?
CN III, IV, V, VI, ciliary ganglion
What are the advantages to a retrobulbar block?
- Post-op analgesia
- Globe immobility during sx
- Decreased anesthetic and NMBD requirements
What are potential complications of a retrobulbar block?
- Retrobulbarr hemorrhage
- Damage to optic nerve or extraocular muscles
- Globe penetration
- Intravascular injection
- Intrathecal injection
What is the preferred technique for a retrobulbar block?
Interior-temporal palpebral
If there is resistance to injection during a retrobulbar block, what does this indicate?
Needle is within the optic nerve sheath and proceeding may be fatal
What nerve does a maxillary nerve block affect?
Sensory branch of CN V
What areas are anesthetised in a maxillary nerve block?
Maxilla and teeth/soft tissues, lateral nasal mucosa
`What are the three techniques for a maxillary nerve block?
- Subzygomatic
- Maxillary tuberosity (intraoral)
- Infraorbital
What does an infraorbital block provide anesthesia for?
3rd premolar and all teeth rostral, rostral maxilla and soft tissues
Where is an infraorbital nerve block placed?
Into the infraorbital foramen
Is an intraoral or extraoral technique perfered in cats?
Extraoral
What does an inferior alveolar block provide anesthesia for?
Mandibular teeth, rostral lower lip, intermandibular space
Where is the injection given for an inferior alveolar block?
Medial aspect of mandible adjacent to mandibular foramen
What other nerve may be affected in an inferior alveolar block?
Lingual nerve- loss of sensory innervation to the rostral 2/3 of tongue
What does a mental block provide anesthesia for?
Rostral lower lip only
Where is the injection places for a mental nerve block?
Over palpable middle mental foramen, intra or extraorally
What does an cervical paravertebral block provide anesthesia for?
Entire thoracic limb including the scapula and shoulder joint
Which nerves are effected in a cervical paravetebral block?
Ventral branches of C6, C7, C8, T1, spinal nerves, proximal to brachial plexus
Are cervical paravertebral blocks commonly used?
No, very technically difficult
What does a brachial plexus block provide anesthesia for?
Thoracic limb below them elbow
Which nerves are effected in a brachial plexus block?
Suprascapular, musculocutaneous, radial, medial, and ulnar
Is a nerve locator preferred when performing a brachial plexus block?
Yes, but ultrasound can be used
What is a RUMM block used for?
Anesthesia of the distal thoracic limb including the carpus
Which nerves are effected by a RUMM block?
Radial, ulnar, median, and musculocutaneous
That’s what RUMM stands for…..
T/F: RUMM blocks are achieved with one injection.
False- two injections are required, one medially and one laterally
T/F: Declaws are illegal in some places.
True
What drug is used for declaw blocks?
Bupivacaine
T/F: Femoral and sciatic blocks are typically performed together.
True
Pelvic limb blocks anesthetize what?
Pelvic limb distal to the mid-femur
T/F: Pelvic limb blocks are as effective as an epidural for stifle surgery.
True
What are some indications for using an intercostal block
Thoracotomy, rib fractures, thoracic procedures, etc
T/F: Intercostal blocks should be performed along the cranial aspect of the rib.
False- the VANs run along the caudal aspect
T/F: Intercostal blocks should be performed at the incision site and the two surrounding rib spaces.
True
What should the orientation of the effected side be when performing intrapleural regional blocks?
Down, because gravity. At least 20 min after injection
Where are epidurals most commonly places in small animals?
L-S space
Should epidurals be performed on awake animals?
No, heavy sedation or anesthesia is required
What are two options for administering an epidural?
- Single injection
2. Indwelling catheter
T/F: Epidurals can be performed with the animal in sternal or lateral recumbancy.
True- sternal is preferred
What is the loss of resistance technique for epidurals?
Feeling for a pop when advancing the needle- indicates you are through the ligaments
Is it recommended to inject air using the LOR technique to confirm placement?
No- use saline or the epidural drug
What is the hanging drop technique for eipdurals?
Watching for the fluid in the hub of the needle to be pulled into the space
What principle does the hanging drop technique work on?
The epidural space being subatmospheric pressure
Is the hanging drop more reliable in large or small patients?
Large
Are nerve locators commonly used in epidurals?
No
T/F: Higher volumes of injection are more likely to spread cranially.
True- risk for sympathetic blockade especially with LA drugs
What volume will be sufficient to reach L1?
0.2 mL/kg
T/F: Most commonly a local anesthetic and an opioid are used in combination in an epidural.
True- usually bupivicaine and morphine
T/F: Morphine produces more cranial spread and a longer duration with an epidural than using a LA alone
True- may produce anesthesia in the thoracic wall/limbs
What are some complications of an epidural injection?
- Intrathecal injection
- Neural damage/toxicity
- Infection
- Hypotension
What are some complications of epidural opioids?
Urinary retention and puritis (uncommon)
