Lipid therapy in poisoning treatment

Abstract

ntravenous (IV) infusion of lipids is a simple, easy to administer and cheap treatment that is becoming an essential intervention in the management of poisoning. IV lipids (i.e. Intralipid® 20%, Fresenius Kabi is the most commonly used, but not the only, parenteral lipid product available) have a place in the management of compounds that are lipophilic or cardiotoxic. Most veterinary cases reported involve baclofen, permethrin and macrocyclic lactones, but lipid infusion may have a place in the treatment of other compounds: the list continues to grow. In most cases, the suitability of a compound for treatment with IV lipid therapy is determined by two factors: its lipophilicity and half-life. Lipid infusion is only suitable for lipophilic compounds with short-to-moderate half-lives; it is not suitable for lipophilic compounds with long half-lives, such as vitamin D compounds (e.g. calciferol, calcipotriol) and anticoagulant rodenticides (e.g. brodifacoum, bromadiolone). The mechanism of action of lipid infusion is not fully understood and there are two main theories: a lipid sink mechanism and a metabolic effect. It is thought that the lipid component formed in the blood acts as a sink for lipophilic drugs, making them unavailable to act on their target receptors. In drugs causing cardiotoxicity, lipids may reduce toxic effects by providing a source of energy to the myocardial cells. The risks of lipid infusion in the context of treatment of drug toxicity are unknown, but it is generally considered safe. Pancreatitis and extravasation with pain and local swelling have been reported as adverse effects in veterinary cases. Administration of lipids in animals receiving therapy with lipophilic drugs, such as propofol, has been raised as a potential concern; however, the use of lipid infusion is expected to reduce the need for such emergency therapy. The potential effect of lipid infusion on concentrations of other therapeutic agents should be weighed in the risk–benefit balance. There is no standard regimen for lipid infusion, and the following bolus/infusion regimen has been recommended as there are occasional reports of recurrence of toxicity following cessation of lipid administration, or where only a bolus dose has been given: a bolus of 1.5–4 ml/kg of a 20% lipid emulsion intravenously, followed by an infusion (0.25 ml/kg/min over 30–60 minutes). There are no published clinical trials evaluating the efficacy or safety of lipid infusion in acutely poisoned human patients but there are a growing number of case reports and small case series in human and veterinary literature. There is also experimental data. Peacock et al (2013) showed that cats with permethrin toxicity who were given lipids had a lower clinical score earlier than controls, and that lipids were a useful therapy in their treatment. In conclusion, lipid infusion is increasingly used in the management of poisoning and should be considered for any animal at risk of serious toxicity after exposure to a lipophilic compound. CA