Analysis of the temporal regression of the QRS widening induced by bupivacaine after Intralipid administration. Study in an experimental porcine model

Sodium bicarbonate reverts electrophysiologic cardiotoxicity of ropivacaine faster than lipid emulsions in a porcine model

Ropivacaine has been described as a safer local anaesthetic (LA); however, serious cardiotoxic accidents have been reported. Intravenous-lipid-emulsion (ILE) therapy during LA intoxication seems to act as an antidote. Sodium bicarbonate is the standard treatment for sodium channel blocker drug toxicity. We compared both antidotes on the reversion of electrophysiologic toxicity induced by ropivacaine. Ropivacaine 5 mg kg^-1 was administered in 24 pigs, and 3 min later, the animals received ILE: 1.5 ml kg^-1  + 0.25 ml kg^-1  min^-1 (ILE group); sodium bicarbonate: 2 mEq kg^-1  + 1 mEq kg^-1  h^-1 (NaHCO₃ group); saline solution (CTL group). Electrophysiological parameters were evaluated for 30 min. The area under the curve (AUC) for the first 5 or 30 min was compared between groups. Ropivacaine induced a lengthening of the PR interval by 17% (P = 0.0001), His-ventricle-interval by 58% (P = 0.001), sinus QRS complex by 56% (P = 0.0001), paced QRS at 150 bpm by 257% (P = 0.0001), and at 120 bpm by 143% (P = 0.0001) in all groups. At 5 min after treatment, sinus QRS in the NaHCO₃ group was shorter than that in the CTL group (AUC_QRS5 , P = 0.003) or ILE group (AUC_QRS5 , P = 0.045). During the first minute, seven of the animals in the NaHCO₃ group vs. two in the ILE or 0 in the CTL group recovered more than 30% of the sinus QRS previously lengthened by ropivacaine (P = 0.003). Sodium bicarbonate reversed the electrophysiological toxicity of ropivacaine faster than ILE and control groups.

Assessment of cardiotoxicity and plasma ropivacaine concentrations after serratus intercostal fascial plane block in an experimental model

Serratus intercostal fascial plane block (SIFPB) has emerged as an alternative to paravertebral block in breast surgery. It involves the administration of high volumes and doses of local anesthetics (LA) that can potentially reach toxic levels. Ropivacaine is widely used in thoraco-fascial blocks; however, there is no information on the plasma concentrations attained after SIPFB and whether they are associated with cardiotoxicity. Plasma concentrations of ropivacaine and its electrophysiological effects were evaluated in eight pigs after bilateral SIFPB with ropivacaine in doses of 3 mg/kg. Plasma concentrations, electrophysiological and hemodynamic parameters were measured sequentially for the following 180 min until the end of the study. The area under the curve, the maximum plasma concentration (C_max) and the time to reach C_max (t_max) were calculated. The median arterial ropivacaine concentration C_max was, 2.34 [1.40 to 3.74] µg/ml. The time to reach the highest concentration was 15 [10 to 20] min. Twenty-five percent of the animals had arterial concentrations above the lower limit concentration of ropivacaine for LA systemic toxicity (3.4 µg/ml). No alterations were observed in the electrophysiological or electrocardiographic parameters except for a prolongation of the QTc interval, from 489 ± 30 to 544 ± 44 ms (Δ11.38 ± 6%), P = 0.01. Hemodynamic parameters remained in the physiological range throughout the study. SIFPB with ropivacaine in doses of 3 mg/kg has reached potentially toxic levels, however, it has not been associated with adverse electrophysiological or hemodynamic effects.

Effects of intravenous lipid emulsions on the reversal of pacing-induced ventricular arrhythmias and electrophysiological alterations in an animal model of ropivacaine toxicity

INTRODUCTION

Ropivacaine is considered to have a wider margin of cardiovascular safety. However, several reports of ventricular arrhythmias (VA) due to ropivacaine toxicity have been documented. Intravenous lipid emulsions (ILEs) have recently been used successfully in the treatment of local anesthetic intoxication. The main objective of the present study was to evaluate the efficacy of the ILEs in the prevention of pacing-induced-VA and electrophysiological alterations in an animal model of ropivacaine toxicity.

METHODS

Nineteen pigs were anesthetized and instrumentalized. A baseline programmed electrical ventricular stimulation protocol (PEVSP) to induce VA was performed. Ropivacaine (5 mg·kg^-1 + 100 μg·kg^-1·min^-1) followed by normal saline infusion (control group n = 8) or intralipid 20% (1.5 mL·kg^-1 + 0.25 mL·kg^-1·min^-1) for the ILE group (n = 8), were administered three minutes after the ropivacaine bolus. PEVSP was repeated 25 min after the onset of ropivacaine infusion. Pacing-induced VA and electrophysiological abnormalities were assessed in both groups. A sham-control group (n = 3) without ropivacaine infusion was included.

RESULTS

Most of the electrophysiological parameters evaluated were affected by ropivacaine: PR interval by 28% (p = 0.001), AV interval by 40% (p = 0.001), sinus QRS by 101% (p = 0.001), paced QRS at a rate of 150 bpm by 258% (p = 0.001), and at 120 bpm by 241% (p = 0.001). Seven animals (87.5%) in the control group and eight animals (100%) in the ILE group developed sustained-VA (p = 0.30). Successful resuscitation occurred in 100% of animals in the ILE group vs. 57% of animals in the control group, p = 0.038. Pacing-induced-VA terminated at the first defibrillation attempt in 75% of the animals in the ILE group vs. 0% in the control group, p = 0.01.

CONCLUSION

Ropivacaine strongly altered the parameters of ventricular conduction, thus facilitating the induction of VA. ILEs did not prevent pacing-induced VA. However, facilitated resuscitation and termination of VA were delivered at the first defibrillation attempt compared to the control group.