Miosis in opioid toxicity

Q: Normal pupillary exam excludes opioid toxicity, and the examiner should look for other causes of decreased mental status?

A) True

B) False

Answer: B

Patients with opioid toxicity do not necessarily need to have constricted pupils (miosis). This can be due to various other reasons. Patients may have simultaneously ingested other medications that are prone to cause pupillary dilatation (mydriasis), such as meperidine and/or sympathomimetics or anticholinergics. In fact, patients can even have larger or dilated pupils.

Studies have shown that decreased respiratory rate is the best predictor of opioid toxicity out of all the vital signs.

#toxicology

#neurology

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References:

1. Ghoneim MM, Dhanaraj J, Choi WW. Comparison of four opioid analgesics as supplements to nitrous oxide anesthesia. Anesth Analg 1984; 63:405.

2. Hoffman JR, Schriger DL, Luo JS. The empiric use of naloxone in patients with altered mental status: a reappraisal. Ann Emerg Med 1991; 20:246.