quick ER math: max dose lidocaine for local anesthesia

13 Nov

BASIC IDEA:

–lidocaine = sodium channel blocker

–block enough sodium channels within axon to temporarily stop conduction, thus no pain signal

–Onset 2-5 min, duration 30-60 min


WHAT’S THE MAX DOSE OF LIDOCAINE I CAN GIVE MY PATIENT?

  • lidocaine alone: max dose 4.5 mg/kg
  • lidocaine WITH epinephrine: max dose 7 mg/kg

QUICK MATH:

Lidocaine 1% (10mg/ml) – max dose 4.5mg/kg

for the average 70kg patient:

70kg * 4.5mg/kg = 315mg

315mg / 10mg/ml = 31.5 ml max

BOTTOM LINE: max dose 1% lidocaine is ~30 ml for average 70kg person


VARIATIONS ON A THEME:

Lidocaine 1% (10mg/ml) + Epi –max dose 7mg/kg
70kg * 7mg/kg = 490mg.
490mg / 10mg/ml = 49 ml max
~50 ml max for 70kg person with 1% lido WITH epi

EXTRAPOLATE GUESTIMATONS:
2% lidocaine, 70kg person: ~15 mL max
(30 mL with 1%, double the concentration means half the volume)
1% lidocaine, 140kg person: ~60mL max
(30 mL with 1% at 70kg, double the weight, double the max dose)
2% lidocaine, 40kg person: ~7-10mL max (actual math gets you 9mL)
(30 mL with 1% at 70kg, halve it for the weight, halve it for the double strength concentration)

and so forth.

References: Tintinalli’s Emergency Medicine: A Comprehensive Study Guide. 7th Edition; picture

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One Response to “quick ER math: max dose lidocaine for local anesthesia”

  1. Joe November 23, 2015 at 07:31 #

    NOTE: Other references also advise a maximum of 300mg per single dose, with at least 2 hour wait before additional doses once max is reached. From “Up to Date”:
    “Anesthesia, local injectable: Varies with procedure, degree of anesthesia needed, vascularity of tissue, duration of anesthesia required, and physical condition of patient; maximum: 4.5 mg/kg/dose not to exceed 300 mg; do not repeat within 2 hours.”

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