Local anesthetic systemic toxicity

Question 1

What is LAST?

Answer 1

a constellation of clinical symptoms associated with high plasma levels of local anesthetic-ranging from dizziness to complete cardiovascular collapse

Question 2

What are the neuro symptoms of LAST?

Answer 2

seizure, agitation, loss of consciousness, dysarthria, perioral numbness, tinnitus, dizziness, dysphoria

Question 3

What are cardio signs of LAST?

Answer 3

bradycardia/asystole, hypotension, tachycardia, VF/VT, hypertension

Question 4

DDX of LAST:

Answer 4

Seizure from other causes
Brady or tachy from other causes
Anaphylaxis
PE

Question 5

How do you manage LAST-what do you do first?
Then what (it’s critical to prevent)
Halt what?
Circulatory support and can you use pressors? What is the antiarrhytmic of choice?
Lipid emulsion therapy?

Answer 5

Stop injecting LA, call for help
Ensure adequate oxygenation and ventilation–this initial step is CRITICAL in preventing hypoxia and acidosis (both of which potentiate local anesthetic toxicity)
Halt seizures-benzos are first line (2-4 mg of midaz)-you could give small doses of prop, but CV depression is a concern
Cir support-IV crystalloid
chest compression if pulselessness, ACLS. Pressors are controversial-if cardiac arrest occurs-epi should be used in small doses (10-100 micrograms)
DO NOT USE vasopressin, CCBs, betablockers or lidocaine in tx of cardiac arrest or arrhythmias-amiodarone is the anti-arrythmic drug of choice?
Lipid emulsion therapy-consider administering at the FIRST sign of toxicity

Question 6

Lipid emulsion therapy-what is the dose? The infusion dose, if not stability not attained, then what? How does it work? If all else fails, then what ?

Answer 6

consider administering at the FIRST sign of toxicity
Dose: 1.5 mL/kg of 20% lipid emulsion bolus (usually 100 mL for most adults)
Infusion of 0.25 mL/kg/min for at least 10 minutes AFTER return of circulatory stability
If stability not attained then consider rebolusing and increasing infusion dose to 0.5 mL/kg/min
Max dose: 10 mL/kg over first 30 minutes.
Don’t use prop d/t fact that amt required to achieve an effect would cause profound circulatory depression?
If all esle fails-CPB if available
Works by acting as a lipid sink? The lipid droplets facilitate accelerated redistribution of drug X to the skeletal muscle and to the liver where it is conjugated to permit
excretion.

Question 7

Why is hypercarbia bad with LAST?

Answer 7

Hypercarbia – Increased PaCO2 lowers the seizure threshold with local anesthetic administration.