Q: Which of the following is the best predictor of severity of acute opioid toxicity?
A) constricted pupils
B) decreased respiration
C) altered mental status
D) decreased bowel sounds
E) altered temperature
Decreased respiratory rate is consistently found to be the best predictor of acute opioid toxicity as well as response to antidote i.e., naloxone.
The pupillary exam can be very unreliable (choice A) as patient may have co-abuse sympathomimetics or anticholinergics. Mental status not necessarily to be depressed in acute opioid toxicity. A patient can be very euphoric. (choice C). Similarly, this is true for bowel sounds (choice D) and temperature (choice E).
Reference: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.