Local Anesthetic Systemic Toxicity

Question 1

What is local anesthetic systemic toxicity?

Answer 1

A constellation of clinical symptoms associated with high plasma levels of local anesthetic, and ranging from dizziness to complete cardiovascular collapse.

Question 2

What are the classic clinical features of local anesthetic systemic toxicity?

Answer 2

Worsening neurologic symptoms with increasing concentration of local anesthetic progressing to seizures, LOC, followed by CV manifestations.

Question 3

What are the neurologic symptoms of local anesthetic systemic toxicity in order from most common to least?

Answer 3

Seizure (68%)
dysarthria, perioral numbness, tinnitus, dizziness, dysphoria (18%)
Agitation (11%)
LOC (7%)

Question 4

What are the cardiovascular signs of local anesthetic systemic toxicity in order from most common to least?

Answer 4

• Bradycardia/asystole (27%)
• hypotension (18%)
• tachycardia (16%)
• VF/VT (13%)
• QRS widening (12%)
• ST changes/chest pain/dyspnea/HYPERtension (9%)
• Ventricular ectopy (5%)

Question 5

What is the differential diagnosis for local anesthetic systemic toxicity?

Answer 5

1. Seizure from other causes
2. Bradycardia, tachycardia, or cardiac arrest from other causes
3. Pulmonary embolus
4. Anaphylaxis
5. Myocardial ischemia/infarction
6. Methemoglobinemia (esp if using benzocaine or prilocaine)

Question 6

What is the management of local anesthetic systemic toxicity?

Answer 6

1. Stop injecting local anesthetic
2. Call for help
3. Ensure adequate oxygenation and ventilation
4. Halt seizures
5. Circulatory support
6. Lipid emulsion therapy
7. CPB/CPR if not responsive to above measures

Question 7

Why should ensuring adequate ventilation and oxygenation precede other steps in the treatment of local anesthetic toxicity?

Answer 7

Hypoxia and acidosis potentiate local anesthetic toxicity.

Question 8

How should one treat seizures from local anesthetic toxicity?

Answer 8

1. Benzodiazepines such as midazolam 2 - 4mg are first-line treatment
2. Propofol in small doses of 20 - 40mg are also acceptable but CV depression is a concern.

Question 9

What is the antiarrhythmic of choice in local anesthetic systemic toxicity?

Answer 9

Amiodarone

Question 10

What medications should be used for treatment of cardiac arrest or arrhythmias in local anesthetic systemic toxicity?

Answer 10

Do not use vasopressin, calcium channel blockers, beta blockers or lidocaine.

Question 11

When should you consider providing lipid emulsion therapy for local anesthetic toxicity?

Answer 11

At the first sign of toxicity even if symptoms are mild.

Question 12

What is the dosing regimen for lipid emulsion therapy?

Answer 12

• 1.5cc/kg of 20% lipid emulsion bolus
• infusion of 0.25 cc/kg/min for at least 10 minutes after return of circulatory stability
• if remains unstable, consider rebolusing and doubling infusion

Question 13

In the absence of lipid emulsion for treatment of local anesthetic systemic toxicity, how much propofol should one use to achieve the same effect?

Answer 13

One should not use propofol because the amount required would cause profound circulatory depression.

Question 14

What is the maximum dose of of lipid emulsion therapy in the first 30 minutes of use?

Answer 14

10 cc/kg

Question 15

If cardiac arrest occurs during local anesthetic systemic toxicity, what vasopressors should be used?

Answer 15

The use of vasopressors is controversial but epinephrine 10 - 100mcg should be used in small doses.