May see some of this on the National! 1) Pathophysiology of opioid overdose in the brain Primary problem: opioids stimulate µ-opioid receptors in the CNS → depress the brainstem respiratory centers (medulla) and blunt the CO₂ drive. - ↓ respiratory rate + ↓ tidal volume → hypoventilation - CO₂ rises (hypercapnia) + O₂ falls (hypoxemia) → respiratory acidosis - Hypoxia → altered mental status → seizures/arrest (late) - Also causes CNS sedation + loss of airway tone → obstruction/aspiration risk High-yield triad: CNS depression + respiratory depression + miosis (miosis can be absent in mixed OD). 2) Why you might need to repeat naloxone (Narcan) Repeat dosing is needed when opioid effect outlasts naloxone or the dose is overwhelming. Common reasons: - Long-acting opioids (methadone, ER formulations) - High potency / large load (e.g., fentanyl analog exposure) - Re-sedation after initial response (short naloxone duration) - Co-ingestants (benzos/EtOH) → patient remains altered even if RR improves (narcan won’t fix benzos) - Inadequate initial dose / wrong route / poor absorption - Delayed GI absorption (body packing, bezoar) Test pearl: Naloxone’s job is ventilation, not “make them awake.” Titrate to adequate RR/ETCO₂. 3) Causes of erythematous skin Erythema = vasodilation/inflammation. On exams, they love pattern recognition: Big buckets: - Infectious: cellulitis, erysipelas, scarlet fever, meningococcemia (may start as erythema), viral exanthems - Allergic/immune: urticaria, anaphylaxis, contact dermatitis, drug eruptions - Heat/vasodilatory: heat illness, fever/flushing, sunburn - Toxicologic: CO exposure (classically “cherry red” is unreliable), niacin flush, anticholinergic vs sympathomimetic syndromes (often flushed) - Shock/inflammatory states: early sepsis (warm, flushed), cytokine reactions - Autoimmune: lupus rash, dermatomyositis, vasculitis Pearl: Erythema + hypotension/wheeze/angioedema = anaphylaxis until proven otherwise.