Clinical exam in acute opioid toxicity

Q: Which of the following is a more reliable sign of acute opioid toxicity? - select one

A) Depressed mental status

B) Decreased respiratory rate

C) Miotic pupils

Answer: B

In acute opioid toxicity, pupils are expected to be constricted, but they can be normal or even larger. It also depends on the type of opioid, like meperidine, overdose tends to present with normal pupils. The co-ingestion of sympathomimetics or antimuscarinics can cause pupils to be larger on exam. In comparison, a decreased respiratory rate of less than 12 by manual counting on the best side is a better toxicity of acute opioid toxicity.

Bradycardia or hypotension from histamine release may occur, but it can't predict opioid toxicity unless the history is very clear. Similarly, normal capnography or hypothermia should not be relied on too much.

Mental status can range from coma to euphoria. The occurrence of a seizure should raise the possibility of tapentadol, tramadol, or meperidine overdose.

Hypoxia and traumatic brain injury (TBI) can be the cause, result, or simultaneously occurring features and require prompt address.

#toxicity

References:

1. Fahmy NR, Sunder N, Soter NA. Role of histamine in the hemodynamic and plasma catecholamine responses to morphine. Clin Pharmacol Ther 1983; 33:615.

3. Viglino D, Bourez D, Collomb-Muret R, et al. Noninvasive End Tidal CO2 Is Unhelpful in the Prediction of Complications in Deliberate Drug Poisoning. Ann Emerg Med 2016; 68:62.

4. Palkovic B, Marchenko V, Zuperku EJ, Stuth EAE, Stucke AG. Multi-Level Regulation of Opioid-Induced Respiratory Depression. Physiology (Bethesda). 2020 Nov 1;35(6):391-404. doi: 10.1152/physiol.00015.2020. PMID: 33052772; PMCID: PMC7864237.