LAST Flashcards
Local anesthetic systemic toxicity is a
serious but rare event during regional anesthesia
most commonly occurs from an inadvertent intravascular injection
___________ is thought to cause seizures
initial blocking of inhibitory neurons
___________ results in bradycardia
blocking of cardiac ion channels
The most serious complication of LAST is
ventricular fibrillation
_________ drugs are thought to be less cardiotoxic
shorter acting drugs
More potent agents have
higher lipid solubility & protein binding
The classic clinical presentation of last includes
rapid onset; usually within a minute
Subjective symptoms of LAST include
agitation, tinnitus, circumoral numbness, blurred vision, and metallic taste
this is followed by muscle twitching, unconsciousness, and seizures
Very high levels of local anesthetic can result in
cardiac and respiratory arrest
The most commonly seen incidences of LAST are a result of
epidural
axillary
interscalene
Ways to prevent LAST include
test dosing
incremental injection with aspiration
use of pharmacologic markers
ultrasound
Treatment of LAST includes:
prompt recognition and diagnosis
airway management priority- seizure suppression with benzodiazepines & succincycholine & prevention of hypoxia & acidosis
Lipid emulsion therapy
vasopressors- epinephrine <1 mg/kg
vasopressin- do not give b/c of risk of pulm. hemorrhage
the possible mechanism of action of lipid emulsion therapy is
capture local anesthetic in blood (lipid sink)
increased fatty acid uptake by mitochondria
interference of Na+ channel binding
promotion of calcium entry
accelerated shunting
The max dose of lidocaine & mepivacaine is
4 mg/kg; 7 mg/kg with epi
The max dose of bupivacaine, ropivacaine, & tetracaine is
3 mg/kg
The max dose of chloroprocaine is
11 mg/kg; 14 mg/kg with epi
The max dose of prilocaine is
7 mg/kg; 8.5 mg/kg with epi
The max dose of procaine is
12 mg/kg
Bupivacaine is most likely to cause
LAST because it is longer acting and has a stronger bond
Nerve injury can be a result of
direct needle trauma or local anesthetic toxicity
The incidence of peripheral nerve injury varies with
location
Pre-existing patient factors for nerve injury include
diabetes, pre-existing neurologic disease, smoking, increased BMI, male
Local anesthetic neurotoxicity is the result of
dose and concentration of local anesthetic
additive agents, e.g. epinephrine
Nerve injury should be evaluated based on
presenting signs & symptoms
Patient’s perception of the postoperative course is altered by
postoperative blur
non-operative factors that coincide with the surgical site
Ultrasound allows the practitioner to identify important structures close to nerve tissue such as
dural, pleural, vasculature, & bowel
