Barbiturate Poisoning and the Role of the Nephrologist
Extracorporeal treatments represent a life-saving intervention for many poisonings. In some instances such as salicylate toxicity, lithium toxicity, and poisoning with volatile alcohols, the indications for initiation of extracorporeal treatment are fairly straightforward. For less common poisons, knowledge about protein binding, volume of distribution, molecular weight, and prior reports of treatment are essential.
Although no longer widely prescribed for insomnia, barbiturates remain in use for treatment of seizure disorders and in veterinary practice. They remain available for abuse or poisoning. The major toxicities of barbiturate poisoning are CNS depression, respiratory depression, and cardiovascular depression. The EXTRIP (Extracorporeal Treatments in Poisoning) workgroup has extensively reviewed the literature regarding extracorporeal treatment of barbiturate poisoning and published a set of recommendations in AJKD based on the physicochemical and pharmacokinetic properties of barbiturates, as well as past experiences with extracorporeal treatments. As there are no randomized controlled trials in humans of extracorporeal treatment for barbiturate poisoning, some of the evidence was obtained from case series and animal studies.
The workgroup notes a difference in the ability to dialyze short acting vs. long acting barbiturates. They categorize the long-acting barbiturate, phenobarbital, as “dialyzable” while the short acting barbiturate, thiopental, is “moderately dialyzable.” For this reason, the workgroup recommends extracorporeal therapy for treatment of severe, long-acting, barbiturate poisoning.
They observe that barbiturate levels do not reliably correlate with a need for extracorporeal treatment. Unlike some other dialyzable toxins where a level can provide insight on when to initiate extracorporeal therapy, the clinical presentation of barbiturate toxicity is a more appropriate guide for which patients to dialyze. Specifically, prolonged coma, respiratory depression requiring mechanical ventilation, or shock represent clinical indications for extracorporeal therapy. Although initial levels do not represent an indication for dialysis, a rising barbiturate level despite treatment with multi-dose activated charcoal is considered an indication for extracorporeal therapy.
With regard to the selection of extracorporeal modality, intermittent hemodialysis is the treatment of choice due to its high rate of clearance and wide availability. Although charcoal hemoperfusion may offer somewhat enhanced clearance, technical challenges, increased expense, and more limited availability make intermittent hemodialysis a better option in most settings.
Considering that treatment of most poisonings represents a true medical emergency and will often occur at night or on weekends, the availability of organized, evidence-based, easily interpretable guidelines for extracorporeal treatments is much appreciated. This is a resource from which all practicing nephrologists as well as toxicologists, emergency room physicians, and other providers will benefit.
John W. O’Bell, M.D.
Assistant Professor of Medicine
Division of Kidney Disease and Hypertension
The Warren Alpert Medical School of Brown University
To view the article full-text or PDF (freely available), please visit AJKD.org.
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