In heroin users specifically, 5% needed either repeat naloxone or oxygen > 2 hours after initial naloxone reversal. Observation for 3 hours may be safer, especially for those with polysubstance abuse.
Thunderclap headache (TCH) is a concerning symptom and requires diagnostic evaluation. Initial head CT w/o contrast can help detect SAH with negative LR of 0.01 if performed within 6h of headache onset. However, a head CT w/o contrast can miss other causes of TCH and may require advanced imaging and LP.