Acute cyanide poisoning: are skin findings and odors helpful in making the diagnosis?

June 19, 2018, 12:48 pm

★★☆☆☆

Challenges in the diagnosis of acute cyanide poisoning. Parker-Cote JL et al. Clin Toxicol 2018;56(7):609-617

Abstract

The stated goal of this somewhat confusing and unfocused article was to “identify isolated acute cyanide poison cases and to identify reported signs, symptoms and laboratory findings.”

The authors did a systematic literature review to retrieve cases reports and case series describing patients who were alive on presentation after acute exposure to a cyanide salt. Patients exposed to cyanide in association with smoke inhalation were excluded.

They found 65 relevant studies (52 case reports and 13 case series) published between 1967 ad 2015, with a total of 102 individual cases. Common clinical characteristics reported included unresponsiveness (78%,) respiratory failure (73%,) arrhythmias (72%,) and hypotension (54%.) There were 26 deaths. Some anecdotally mentioned distinguishing characteristics of cyanide poisoning were reported only infrequently. A bitter almond odor was documented in 15% of cases, and cherry red skin in 11%.

In general, I have little patience with studies such as this that attempt to analyze clinical characteristics of a condition from case reports in the medical literature. The problems of incomplete data reporting from a wide variety of clinicians with different abilities, observation skills, and compulsiveness seem insurmountable. (I have the same problems with papers analyzing cases from poison information center databases.

So, was “cherry red skin” actually present only present in 11% of cases, or did it occur more frequently but wasn’t note or detected? There’s no way to tell.

The authors conclude that one can not rely on skin findings or specific odors to diagnosis cyanide toxicity. This is certainly correct. Interestingly, the authors also conclude that:

Clinicians should keep a high level of suspicion for cyanide toxicity for an unresponsive, hemodynamically unstable patient with significant persistent lactic and metabolic acidosis . . .

This is an important point, and certainly correct. But amazingly, it is in no way supported by the data the authors present. Unless I missed something, there was absolutely nothing about lactic acidosis in their data, nor any indication about how to define “significant persistent lactic acidosis.” In fact, despite the stated goal as quoted above, there were no data presented about laboratory findings at all. this seems a very strange omission.

Related post:

Hydroxocobalamin vs. Sodium Nitrite: Cyanide Antidote Smackdown

Potassium cyanide ingestion and hydroxocobalamin

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