Hemodialysis in acute methanol poisoning: is there really good evidence?
February 16, 2015, 11:11 pm
Recommendations for the Role of Extracorporeal Treatments in the Management of Acute Methanol Poisoning: A Systematic Review and Consensus Statement. Roberts DM et al. Crit Care Med 2015 Feb;43:461-472.
The Extracorporeal Treatment in Poisoning (EXTRIP) Workgroup was established to provide evidence-based guidance on the use of hemodialysis and other methods of extracorporeal treatment in various toxic exposures. The workgroup has published previous papers giving their recommendations regarding poisoning by acetaminophen, lithium, carbamazepine, barbiturate, tricyclic antidepressants, and thallium.
This is a tremendously ambitious project, involving experts from many fields of medicine and pharmacology, and extensive review of the literature. Unfortunately, for many of these intoxications, good evidence simply does not exist. In this instance, all of the major recommendations regarding methanol are rated as 1D. The rating of “1” indicates a “strong recommendation.” A level of evidence rated “D” is described in the paper thusly: “very low level of evidence (our estimate of the effect is just a guess, and it is very likely that the true effect is substantially different from our estimate of the effect.)”
That last statement is refreshingly honest. I’ve disagreed with some members of the workgroup in the past about this, but I still believe you can’t make real evidence-based recommendations on the basis of poor evidence. Rather than the word “guess,” I’d say that these recommendations are opinions. But given the extensive toxicology experience of members of EXTRIP, it is essential to engage with these consensus opinions. In addition, there is a wealth of pharmacologic and toxicologic information about methanol toxicity in this paper, and I’d consider it a must read.
For the record, here are the major recommendations in the paper:
Extracorporeal Treatment in a Patient with Methanol Poison is Recommended in the Following Circumstances:
1) Severe toxicity, including any of:
c) new visual deficits
d) metabolic acidosis (pH < 7.15 or persistent acidosis despite supportive treatment)
e) anion gap > 24 mmol/L
2) Serum methanol concentration
a) > 70 mg/dL in context of fomepizole therapy
b) > 60 mg/dL in context of ethanol treatment
c) > 50 mg/dL in absence of alcohol dehydrogenase blocker therapy
3) impaired kidney function (for definition, see supplement)
Again, all of these are 1D recommendations. Make of that what you will.