Excellent review of lipid rescue therapy
February 25, 2015, 6:47 pm
Intravenous Lipid Emulsion in the Emergency Department: A Systematic Review of Recent Literature. Cao D et al. J Emerg Med 2014 Dec 19 [Epub ahead of print]
This excellent comprehensive review of lipid rescue therapy (LRT) is vitiated only by the unavoidable fact that available clinical evidence is so inconclusive. As the authors point out, published literature consists mostly of case reports and small case series. The vast majority of these reported cases have good outcomes and reflect positive effects from ILE, but the evidence is marred by multiple confounding variables (such as concurrent treatment) that are impossible to correct for, and by publication bias. There have been no prospective randomized controlled trials.Intravenous lipid emulsion is now considered first-line therapy for local anesthetic systemic toxicity (LAST,) but generally reserved as a last-ditch effort for patients severely ill from other drugs who are not responding to more established interventions.
The authors conducted an extensive literature review to identify publications describing human overdose cases treated with LRT in which outcomes were reported. They found 94 articles and 40 abstracts, which are cited in a very complete bibliography current to 2014.
This entire review is well worth reading. I will touch on some points I found particularly interesting.
Table 1 lists the different drugs involved in overdose cases where LRT was used, along with whether the observed result was “positive effect” or “no apparent effect.” (For some reason they do not report possible negative effects, although one article cited in their reference list described 2 patients who developed asystole shortly after receiving LRT.) The list includes:
- local anesthetics (primarily bupivacaine)
- anti-depressants (including amitriptyline, citalopram, bupropion, and venlafaxine)
- anti-psychotics (including quetiapine and olanzapine)
- cardiovascular medications (primarily calcium-channel-blockers, beta-blockers and anti-arrhythmics)
There are cases cited of overdose with various other agents, including aconite, lamotrigine, baclofen, and chloroquine. Most of the drugs involved were lipophilic, but positive effects were observed also with water-soluble drugs, such as metoprolol, atenolol, labetalol, and amphetamine.
The authors note that at this time the recommendations for LRT dosing in overdose cases is empiric, based on the experience with treating LAST. They do not discuss a point we touched on in our recent podcast with Dr. Guy Weinberg. With LAST, a relatively large dose of toxic agent is rapidly taken up systemically, and quickly eliminated if the patient survives. With an oral overdose, systemic absorption can continue for hours or even days. Optimal LRT treatment in these cases might require a completely different dosing schedule. Unfortunately, that question has not been studied.