Lipid Emulsion to Treat Acute Poisonings: Mechanisms of Action, Indications, and Controversies

Biodetoxification using intravenous lipid emulsion (ILE) in acute poisoning is of growing interest. As well as for local anesthetics, ILE is currently used to reverse toxicity caused by a broad-spectrum of lipophilic drugs. Both pharmacokinetic and pharmacodynamic mechanisms have been postulated to explain its possible benefits, mainly combining a scavenging effect called "lipid sink" and cardiotonic activity. Additional mechanisms based on ILE-attributed vasoactive and cytoprotective properties are still under investigation. Here, we present a narrative review on lipid resuscitation, focusing on the recent literature with advances in understanding ILE-attributed mechanisms of action and evaluating the evidence supporting ILE administration that enabled the international recommendations. Many practical aspects are still controversial, including the optimal dose, the optimal administration timing, and the optimal duration of infusion for clinical efficacy, as well as the threshold dose for adverse effects. Present evidence supports the use of ILE as first-line therapy to reverse local anesthetic-related systemic toxicity and as adjunct therapy in lipophilic non-local anesthetic drug overdoses refractory to well-established antidotes and supportive care. However, the level of evidence is low to very low, as for most other commonly used antidotes. Our review presents the internationally accepted recommendations according to the clinical poisoning scenario and provides the precautions of use to optimize the expected efficacy of ILE and limit the inconveniences of its futile administration. Based on their absorptive properties, the next generation of scavenging agents is additionally presented. Although emerging research shows great potential, several challenges need to be overcome before parenteral detoxifying agents could be considered as an established treatment for severe poisonings.

Hemodynamic Effects of Intravenous, High-Dose Lipid Emulsion With and Without Metoprolol Infusion in Healthy Volunteers: A Randomized Clinical Trial

In a double-blinded, randomized, crossover trial, we investigated the hemodynamic effects of high-dose intravenous lipid emulsion (ILE) with/without metoprolol. Ten healthy volunteers each completed 4 trial days (placebo + ILE; metoprolol + placebo; metoprolol + ILE; placebo + placebo) in random order. Metoprolol was administered as an initial bolus (10 mg), followed by an infusion (50 mg) from 5 to 30 minutes. ILE was administered as a bolus at 12.5 minutes (2.5 mL/kg), followed by a 15-minute infusion (0.25 mL/kg per minute). On metoprolol + ILE days (compared with metoprolol + placebo) after 120 minutes, mean heart rates were significantly higher (difference, 5.5 beats per minute (bpm); 95% confidence interval (CI), 3.0-8.1 bpm; P < 0.001), and average relative cardiac output was higher (difference, 10 percentage points; 95% CI, 5-15 percentage points; P < 0.001). The hemodynamic effect of ILE developed gradually. ILE had no effect on plasma metoprolol or major adverse events. In conclusion, high-dose ILE has relatively marginal and delayed hemodynamic effects that may have limited clinical relevance in the short-term clinical toxicological setting.

Intravenous Lipid Emulsions in Veterinary Clinical Toxicology

Use of intravenous lipid emulsion (ILE) as an antidote for severe cardiotoxicity and neurotoxicity has expanded in the veterinary world in the past decade. Despite advances in understanding of potential mechanisms of action of antidotal ILE, knowledge gaps remain in efficacy, appropriate dosing rates for various toxicants, and potential adverse reactions. Use of ILE in management of toxicoses of veterinary patients should be considered investigational, and should not be first-line treatment of most toxicoses, especially where established treatment protocols have good likelihood of positive outcomes. Use of ILE in veterinary toxicology cases requires judicious assessment of individual cases and proper informed consent of clients.

Lipid emulsion in local anesthetic toxicity

PURPOSE OF REVIEW

Enthusiasm for regional anesthesia has been driven by multimodal benefits to patient outcomes. Despite widespread awareness and improved techniques (including the increasing use of ultrasound guidance for block placement), intravascular sequestration and the attendant risk of local anesthetic systemic toxicity (LAST) remains. Intravenous lipid emulsion (ILE) for the treatment of LAST has been endorsed by anesthetic regulatory societies on the basis of animal study and human case report data. The accumulated mass of reporting now permits objective interrogation of published literature.

RECENT FINDINGS

Although incompletely elucidated the mechanism of action for ILE in LAST seemingly involves beneficial effects on initial drug distribution (i.e., pharmacokinetic effects) and positive cardiotonic and vasoactive effects (i.e., pharmacokinetic effects) acting in concert. Recent systematic review by collaborating international toxicologic societies have provided reserved endorsement for ILE in bupivacaine-induced toxicity, weak support for ILE use in toxicity from other local anesthetics, and largely neutral recommendation for all other drug poisonings. Work since publication of these recommendations has concluded that there is a positive effect on survival for ILE when animal models of LAST are meta-analyzed and evidence of a positive pharmacokinetic effect for lipid in human models of LAST.

SUMMARY

Lipid emulsion remains first-line therapy (in conjunction with standard resuscitative measures) in LAST. Increasing conjecture as to the clinical efficacy of ILE in LAST, however, calls for high-quality human data to refine clinical recommendations.

Effect of lipid emulsion infusion on paliperidone pharmacokinetics in the acute overdose rat model: A potential emergency treatment for paliperidone intoxication

Paliperidone prolongs cardiac repolarization in a concentration-dependent manner. Meanwhile, continuous infusion of intravenous lipid emulsion (ILE) has been established as a detoxification therapy for lipophilic drugs. However, this change in pharmacokinetics of various drugs following ILE administration remains to be clarified. Our objective is to clarify the effect of continuous infusion of ILE on the pharmacokinetics of overdosed paliperidone in rats. Paliperidone (20mg/kg) was administered orally to free-moving male Wistar rats. Continuous infusion (initial loading dose: 4ml/kg for 10min, followed by 4ml/kg/h for 12h) of ILE or acetated Ringer's solution (AR) was initiated 30min after paliperidone administration. Plasma concentration profile of paliperidone was monitored for 12h after administration. The plasma concentration and tissue/plasma concentration ratios of paliperidone were compared between ILE and AR groups. The rat group infused with ILE showed a higher area under the concentration-time curve (mean [S.D.]: 6102 [900.9] vs. 3407 [992.1]nghml^-1, p=0.02) and longer elimination half-time (t_1/2) (4.1 [0.9] vs. 2.2 [0.4]h, p=0.02) compared with the AR group. Tissue/plasma concentration ratios of paliperidone were lower in ILE rats than in AR rats (1.98 [0.70] vs. 3.82 [1.47] in the heart, p=0.04; 0.28 [0.29] vs. 1.27 [0.58] in the brain, p<0.001). In conclusion, continuous infusion of ILE would reduce tissue distribution and prolonged the t_1/2 of paliperidone in rats. These results suggest that continuous infusion of ILE has potential as an emergency treatment for acute paliperidone intoxication.