Differential recovery of ventricular repolarization and hemodynamics following bupivacaine and ropivacaine intoxication: the impact of lipophilicity on lipid emulsion efficacy.

Introduction: Local anesthetic systemic toxicity (LAST) causes significant ventricular repolarization disturbances. While intravenous lipid emulsion (ILE) is the standard treatment, the factors governing the simultaneous recovery of electrical and mechanical functions remain unclear. We evaluated ILE efficacy in reversing repolarization alterations and hemodynamic collapse induced by clinically equipotent doses of bupivacaine and ropivacaine. Methods: Twelve swine were randomized to receive a toxic bolus of bupivacaine (4 mg/kg) or ropivacaine (5 mg/kg). The primary outcome was the Area Under the Curve (AUC) of the corrected T-peak to T-end interval (Tp-TeC) during the recovery phase. Secondary outcomes included QTc and mean blood pressure (MBP) AUCs. Analysis was divided into a toxicity induction phase (0-3 min) and a recovery phase (3-25 min) to integrate the magnitude and duration of the alterations. Results: Both anesthetics significantly impaired repolarization, with no differences in total toxic load during the initial phase ( Conclusion: Our findings demonstrate a distinct pharmacological divergence in lipid resuscitation therapy. Bupivacaine's higher lipophilicity (Log D) enhances electrical recovery via a more efficient "lipid shuttle" effect on ion channels, while ropivacaine's lower intrinsic cardiotoxicity allows for a more resilient mechanical recovery. These results suggest that electrical and mechanical rescue are governed by different rules dictated by the anesthetic's physicochemical properties.