Bupivacaine-Induced QRS Prolongation is Enhanced by Lidocaine and by Phenytoin in Rabbit Hearts

Procaine, a state-dependent blocker, inhibits HERG channels by helix residue Y652 and F656 in the S6 transmembrane domain

The article evaluated the inhibitory action of procaine on wild-type and mutated HERG potassium channel current (I(HERG)) to determine whether mutations in the S6 region are important for the inhibition of I(HERG) by procaine. HERG channels (WT, Y652A, and F656A) were expressed in Xenopus laevis oocytes and studied using the standard two-microelectrode voltage-clamp technique. The results revealed that WT HERG is blocked in a concentration-, voltage-, and state-dependent manner by procaine ([IC₅₀] = 34.79 μM). The steady state activation curves slightly move to the negative, while inactivation parameters move to the positive in the presence of procaine. Time-dependent test reveals that voltage-dependent I(HERG) blockade occurs extremely rapidly. Furthermore, the mutation to Ala of Y652 and F656 produce about 11-fold and 18-fold increases in IC₅₀ for I(HERG) blockade, respectively. Simultaneously, for Y652A, the steady state activation and inactivation parameters are shifted to more positive values after perfusion of procaine. Conclusively, procaine state-dependently inhibits HERG channels (WT, Y652A, and F656A). The helix residues Y652 and F656 in the S6 transmembrane domain might play a role in interaction of the drug with the channel.

Pharmacokinetic Compatibility Study of Lidocaine with EXPAREL in Yucatan Miniature Pigs

We explored the potential for EXPAREL to interact with lidocaine. Sixty (60) male Yucatan Swine were randomized into 20 groups (N = 3/group). EXPAREL (2 or 4 mg/kg) and/or lidocaine HCl solution 1% or 2% (with epinephrine 1 : 200,000) were injected subcutaneously along a 5 cm virtual incision line. The effects on the pharmacokinetics of bupivacaine and lidocaine were examined when 5, 10, 20, and 40 minutes had passed between administration of lidocaine and EXPAREL. Systemic exposure to lidocaine was increased (AUC_0−24 hr by 48%; C_max by 1,640%) when lidocaine (4 mg/kg) was followed 5 minutes later by EXPAREL (4 mg/kg) compared to lidocaine administered alone. Plasma bupivacaine was increased (AUC_0−24 hr by 50–95%; C_max by 67–1,000%) when lidocaine (4 mg/kg) was followed 5 or 10 minutes later by EXPAREL (4 mg/kg) compared to EXPAREL alone. While EXPAREL should not be admixed with lidocaine, this study shows that local administration of EXPAREL after at least 20 minutes following local administration of lidocaine did not increase the release of either drug.

Reversal of bupivacaine-induced cardiac electrophysiologic changes by two lipid emulsions in anesthetized and mechanically ventilated piglets

BACKGROUND

Accidental IV administration of bupivacaine can compromise cardiovascular function by inducing lethal arrhythmias whose hemodynamic consequences may be alleviated by lipid emulsions. However, little is known about the electrophysiologic effects of lipid emulsions. In this study, we assessed whether 2 different lipid emulsions can reverse cardiac electrophysiologic impairment induced by the IV administration of bupivacaine in anesthetized and mechanically ventilated piglets.

METHODS

Bupivacaine (4 mg . kg(-1)) was injected over a 30-second period in 26 piglets. Thirty seconds after the end of bupivacaine injection, 1.5 mL . kg(-1) saline solution for the control group, and long-chain triglyceride emulsion (LCT group) or a mixture of long-chain and medium-chain triglyceride emulsion (LCT/MCT group) were infused over 1 minute. Cardiac conduction variables and hemodynamic variables were monitored for 30 minutes after injection.

RESULTS

Bupivacaine induced similar electrophysiologic and hemodynamic changes. After 3 minutes, His ventricle intervals (median and interquartiles) were 100 (85-105), 45 (35-55), and 53 (48-73) milliseconds in the control, LCT, and LCT/MCT groups, respectively (P < 0.001 between control and both lipid emulsion groups). Lipid emulsions also reversed the effects on QRS duration, atrial-His, and PQ (the onset of the P wave to the Q wave of the QRS complex) intervals. LCT/MCT emulsion restored the decrease in maximal first derivative of left ventricular pressure (P < 0.01 after 3 minutes versus control group).

CONCLUSIONS

LCT and LCT/MCT emulsions reversed the lengthening of His ventricle, QRS, atrial-His, and PQ intervals induced by the IV injection of 4 mg . kg(-1) bupivacaine.

Severe central nervous system and cardiovascular toxicity in a pediatric patient after ingestion of an over-the-counter local anesthetic

Dibucaine is considered one of the most potent and consequently toxic amide anesthetics available, and despite withdrawal from the US market as a spinal anesthetic, it remains accessible as an over-the-counter preparation in the United States. Dibucaine exposures in children are infrequently encountered, but to date, all reported consequential ingestions have resulted in death. We report the first case of a potentially fatal dibucaine-induced wide-complex arrhythmia in a child who survived her clinical course without sequelae. It is our hope that this report will highlight the toxicity of dibucaine and prompt a review of its over-the-counter status. The rationale and success of a new antidote, 20% lipid emulsion, for the management of local anesthetic toxicity is discussed.