There is no real evidence on treating calcium channel blocker overdose
November 6, 2014, 8:06 pm
Treatment of calcium channel blocker poisoning: A systematic review. St-Onge M et al. Clin Toxicol 2014 Nov;52:926-944.
This systematic review is massive, thorough, intimidating, and all but unreadable.
As a prelude to establishing a clinical guideline for treatment of calcium channel blocker (CCB) overdose, the 14 Canadian authors systematically searched and evaluated relevant literature. They initially identified 15,577(!) citations, from which two reviewers selected 216 for analysis. These included case reports, case series, animal trials, and observational studies. No eligible controlled trials were found.
Not surprisingly, the results of these disparate studies were all over the map, with the quality of evidence judged to be low to very low. Slogging through a discussion of all this that ultimately does not reach any clinically useful conclusion is very tedious. The authors conclude:
This systematic review found a low level of evidence supporting the use of high-dose insulin and extracorporeal life support, and a very low level of evidence supporting the use of calcium, dopamine, norepinephrine, and epinephrine for the treatment of CCB poisoning. This systematic review focused on important outcomes for decision-making in managing patients poisoned with CCB. Controlled clinical trials involving vasopressors, calcium, high-dose insulin, and extracorporeal life support should be performed.
Really? I think that such studies would be labor-intensive, expensive, and impossible to accomplish in any way that would yield convincing data. There are just too many variables and confounders. Therefore, we will never have real evidence-based guidelines on treating CCB overdose, and will have to muddle-through as best we can using available data. As Jerry Hoffman noted in a session at last week’s ACEP Scientific Assembly in Chicago, “Guidelines should regularly conclude that there is no evidence. Full stop.”
However, the paper is a valuable source of references (234 citations!) for anyone researching the topic.