Assessing optimal lidocaine dosing during the acute management of ventricular arrhythmias following myocardial infarction or during cardiac manipulation such as surgery.
Assessing potential lidocaine toxicity.
Lidocaine is commonly used as a local anesthetic, but is also effective at controlling ventricular arrhythmia and ventricular fibrillation in children and adults. For cardiac therapy, optimal therapeutic response is seen when serum concentrations are between 1.5 and 5.0 mcg/mL. Lidocaine is protein-bound (60-80%), primarily to alpha-1-acid glycoprotein; concentrations of this protein increase after myocardial infarction, which may decrease the amount of free lidocaine and thus its efficacy.
Lidocaine undergoes extensive first-pass hepatic metabolism and therefore is not administered orally. It is eliminated via renal clearance, with a half-life of approximately 1.5 to 2 hours. Diseases that reduce hepatic or renal function reduce clearance and prolong elimination of lidocaine.
Toxicity occurs when the serum concentration of lidocaine is >6.0 mcg/mL and is usually associated with symptoms of central nervous system excitation, light-headedness, confusion, dizziness, tinnitus, and blurred or double vision. This can be accompanied by bradycardia and hypotension leading to cardiovascular collapse.
Therapeutic: 1.5-5.0 mcg/mL
Critical value: >6.0 mcg/mL
Optimal response to lidocaine occurs when the serum concentration is between 1.5 and 5.0 mcg/mL.
Toxicity is more likely when concentrations exceed 6.0 mcg/mL.