Lipid Resuscitation of Bupivacaine Toxicity

Background The superiority of Intralipid, a long-chain triglyceride (LCT) emulsion versus Lipovenoes, a long- and medium-chain triglyceride (LCT/MCT) emulsion, in reversing local anesthetic-induced cardiac arrest is poorly defined and needs to be determined. Methods The study included two parts: in experiment A, bupivacaine (20 mg/kg) was injected to produce asystole. Either Intralipid 20% (LCT group, n = 30) or Lipovenoes 20% (LCT/MCT group, n = 30) with epinephrine was infused immediately. Return of spontaneous circulation and recurrence of asystole after resuscitation were recorded. In experiment B, 80 rats using the same model and resuscitation protocol were divided into 10 groups: LCT₀, LCT₁₅, LCT₃₀, LCT₆₀, and LCT₁₂₀ and LCT/MCT₀, LCT/MCT₁₅, LCT/MCT₃₀, LCT/MCT₆₀, and LCT/MCT₁₂₀ (n = 8 each; the subscripts represent respective observation period). LCT₁₅-LCT₁₂₀ and LCT/MCT₁₅-LCT/MCT₁₂₀ groups received Intralipid 20% or Lipovenoes 20%, respectively. Plasma and myocardial bupivacaine and triglyceride concentrations, as well as myocardial bioenergetics, were determined. Results In experiment A, 24 rats in LCT group and 23 in LCT/MCT group achieved return of spontaneous circulation (P = 0.754); among them, 2 (8.3%) and 8 (34.8%) rats suffered a repeated asystole, respectively (P = 0.027). In experiment B, plasma and myocardial bupivacaine concentrations in LCT₁₅ and LCT₆₀ groups were lower than LCT/MCT₁₅ and LCT/MCT₆₀ groups, respectively. Furthermore, the plasma bupivacaine level in LCT/MCT₆₀ group was higher than LCT/MCT₃₀ group (P = 0.003). Conclusions LCT emulsion may be superior to LCT/MCT emulsion in treating bupivacaine-related cardiotoxicity as it was associated with fewer recurrences of asystole after resuscitation and lower myocardial bupivacaine concentrations.