An assessment of the in vivo effects of intravenous lipid emulsion on blood drug concentration and haemodynamics following oro-gastric amitriptyline overdose

The objective was to asses the efficacy of lipid emulsion as antidotal therapy outside the accepted setting of local anesthetic toxicity. Literature was accessed through PubMed, OVID (1966-February 2009), and EMBASE (1947-February 2009) using the search terms "intravenous" AND ["fat emulsion" OR "lipid emulsion" OR "Intralipid"] AND ["toxicity" OR "resuscitation" OR "rescue" OR "arrest" OR "antidote"]. Additional author and conference publication searches were undertaken. Publications describing the use of lipid emulsion as antidotal treatment in animals or humans were included. Fourteen animal studies, one human study, and four case reports were identified. In animal models, intravenous lipid emulsion (ILE) has resulted in amelioration of toxicity associated with cyclic antidepressants, verapamil, propranolol, and thiopentone. Administration in human cases has resulted in successful resuscitation from combined bupropion/lamotrigine-induced cardiac arrest, reversal of sertraline/quetiapine-induced coma, and amelioration of verapamil- and beta blocker-induced shock. Management of overdose with highly lipophilic cardiotoxic medications should proceed in accord with established antidotal guidelines and early poisons center consultation. Data from animal experiments and human cases are limited, but suggestive that ILE may be helpful in potentially lethal cardiotoxicity or developed cardiac arrest attributable to such agents. Use of lipid emulsion as antidote remains a nascent field warranting further preclinical study and systematic reporting of human cases of use. (c) 2009 by the Society for Academic Emergency Medicine

There is a need for a rapid predictor of potential clinical severity to guide therapy in patients with an acute overdose of tricyclic antidepressant drugs. We performed a prospective study of 49 such patients to observe the associations among serum drug levels, maximal limb-lead QRS duration, and the incidence of seizures and ventricular arrhythmias. Patients were divided into two groups on the basis of maximal limb-lead QRS duration. Group A (13 patients) had a duration of less than 0.10 second, and Group B (36 patients) had a QRS duration of 0.10 second or longer. No seizures or ventricular arrhythmias occurred in Group A. In Group B there was a 34 per cent incidence of seizures and a 14 per cent incidence of ventricular arrhythmias. All patients survived. Serum drug levels failed to predict the risk of seizures or ventricular arrhythmias accurately. Seizures occurred at any QRS duration of 0.10 second or longer (P less than 0.05), but ventricular arrhythmias were seen only with a QRS duration of 0.16 second or longer (P less than 0.0005). We conclude that determination of the maximal limb-lead QRS duration predicts the risk of seizures and ventricular arrhythmias in acute overdose with tricyclic antidepressants. Serum drug levels are not of predictive value.

Lipid infusion is useful in reversing cardiac toxicity of local anesthetics, and recent reports indicate it may be useful in resuscitation from toxicity induced by a variety of other drugs. While the mechanism behind the utility of lipid rescue remains to be fully elucidated, the predominant effect appears to be creation of a "lipid sink".