Regional anesthetic techniques Flashcards
Features of amino amide structure & examples:
hepatic metabolism (slower), but toxic accumulation is more likely
ex. lidocaine, bupivacaine, mepivacaine
MOA local anesthetics?
block sodium channel
Local anesthetics are considered weak bases? T/F
True, ( becomes ionized in acidic pH causing ion trapping)
- reason should not inject lidocaine into infected tissues which are considered acidic/ so LA does not work
Which local anesthetic has a short onset & short duration?
Lidocaine: fast onset & 1-2 hr duration–> max dose: 5 mg/kg
What fiber types are more susceptible to local anesthetic?
smaller nerve & myelinated fibers
Local anesthetic toxicity is associated with…
high dose, IV injection & reduced biotransformation/ elimination (liver or renal)
What CNS signs are associated with local anesthetic toxicity?
depression of cortical inhibitory pathways, impaired vision, seizures, CNS depression/coma
What CV signs are associated with local anesthetic toxicity?
bradycardia, changes to ECG, VPC, reduced myocardial contractility & cardiac arrest
Topical anesthesia- block indications
superficial mucosal tissue
Topical anesthesia- what nerves are blocked?
free nerve endings & nociceptors
Local infiltration- block indications
skin & underlying tissue
Local infiltration- nerves blocked
free nerve ending, nociceptors & terminal nerve branches (does not target specific nerve)
What do intraneural injections produce?
Nerve damage
Infraorbital nerve block contraindication
risk of ocular puncture in cats & brachycephalic animals!
Maxillary nerve block:
o Nerves blocked: maxillary
o Use: dental; unilateral mandible
o Area desensitization: maxilla (+teeth), paranasal sinus & sinus cavity
Inferior alveolar (mandibular) nerve block:
o Nerves blocked: mandibular nerve (branch of trigeminal)
o Use: dental; mandibular teeth extraction
o Area desensitization: mandible, mandibular teeth & ipsilateral lower lip
Inferior alveolar (mandibular) block adverse effect?
desensitize lingual nerve leading to self mutilation of the tongue during recovery
Why would you select lumbar paravetebral block over inverted L technique?
no LA at margins of surgical site & provides better analgesia than an inverted l technique
What nerves are being blocked with the lumbar paravertebral block?
T13-L1 &L2
Where is the epidural space?
located between interarcutae ligament & duramater
What epidural space is commonly used in SA?
o Lumbo-sacral space is used in small animal (less risk of piercing spinal cord- since it ends at L6-L7)
What epidural space is commonly used in LA?
o Sacro-coccygeal space because spinal cord ends at S1
Landmark for epidural injection- SA?
o Iliac crest, medial sacral crest & spinous process L7
Why is it important to know whether you are epidural or spinal injection?
They need different volumes of LA; which spinal injection requires much lower dose than epidural space!
How do you know if you are in the epidural space?
Hanging drop technique OR loss of resistance to injection
Why should you use small volumes in the sacro-coccygeal epidural in horses?
Typically use a small amount in horses, because large volumes can lead to pelvic limb paralysis
