[Dose limits for local anesthetics. Recommendations based on toxicologic and pharmacokinetic data].

Abstract

Since Heinrich Braun added adrenaline to cocaine (and later also to procaine) in 1903 to allow clinical use of this local anesthetic, "limiting dosages" for local anesthetics have been "recommended" with no reference to the technique of administration, on the assumption that adrenaline will lower the toxicity of the local anesthetic used. However, the limiting dosages determined up to now do not take account of important pharmacokinetic and toxicological data: (1) The dependence of blood levels measured on the technique of regional anesthesia and (2) the raised toxicity of a local anesthetic solution containing adrenaline following inadvertent intravascular (intravenous) injection. A maximum dose recommendation that differs according to the technique of local anesthesia is suggested for (A) subcutaneous injection, (B) injection in regions of high absorption, (C) single injection (perineural, e.g. plexus), (D) protracted injection (catheter, combined techniques), (E) injection into vasoactive regions (near to the spinal cord, spinal, epidural, sympathetic). This sequential categorization also underscores the need for selection of appropriate techniques as well as for concomitant monitoring referred to the technique of administration and to the expected and the possible plasma level curve.(ABSTRACT TRUNCATED AT 250 WORDS)