J Korean Pain Soc.  1999 May;12(1):36-42.

The Plasma Concentrations and Systemic Toxicity of Lidocaine after Maximal or Supramaximal Recommended Doses of Epidural Administration

• Park HS
• Jeong CJ
• Chin YJ

Abstract

BACKGROUND: The current maximal recommended doses of lidocaine are 7 mg/kg with 5 microgram/ml of epinephrine. But in clinical practice, sometimes more doses of lidocaine are required to produce adequate regional anesthesia. METHOD: Twenty-two healthy women patients were divided into two groups and pretreated with valium 5 mg p.o, morphine 5 mg i.m., and midazolam 2 mg i.v. before operation. Of these, 7 mg/kg of 2% lidocaine with 5 microgram/ml of epinephrine were given to 11 patients epidurally. Initial 3 ml of epinephrine mixed lidocaine was given as a test dose and remaining doses were given 5 ml/30 sec with 3 min intervals. Radial arterial blood were drawn at 5, 10, 15, 20, 30, 45, 60, 90, 120 min to measure plasma lidocaine concentrations. After confirming all of the peak plasma concentrations of 7 mg/kg lidocaine were absolutely under 5 microgram/ml, the other 11 patients were given 10 mg/kg of 2% lidocaine with 5 microgram/ml of epinephrine epidurally and blood samplings were taken according to the same method of 7 mg/kg group. The peak plasma concentration (C(max)), time to reach to C(max) (T(max)), time to reach to T4, maximal sensory block level, systemic toxicity, and vital sign changes were investigated. RESULT: C(max) was significantly higher in 10 mg/kg group (5.1+/-1.3 microgram/ml) than 7 mg/kg group(3.3+/-0.5 microgram/ml), but T(max) (10.5+/-2.7 min vs 10.9+/-3.1 min) was not different. Time to reach T4 was significantly shorter in 10 mg/kg group (9.5+/-2.7 min) than 7 mg/kg group (12.7+/-3.2 min) but maximal sensory block level (T3.7+/-0.7vsT2.7+/-10) was not different. In four patients of 10 mg/kg group, peak plasma concentrations exceeded 5 microgram/ml, but no systemic toxicities appeared. No significant vital sign changes were observed.
CONCLUSION
The current maximal recommended doses of lidocaine, merely based on body weight are not always appropriate. Further studies are needed to determine more precise guideline of maximal doses that include various pharmacokinetic components.

Keyword

Anesthetic technique, epidural; Anesthetics, local, lidocaine

MeSH Terms

Anesthesia, Conduction
Body Weight
Diazepam
Epinephrine
Female
Humans
Lidocaine*
Midazolam
Morphine
Plasma*
Vital Signs
Diazepam
Epinephrine
Lidocaine
Midazolam
Morphine