Pharmacology · Year 2 · from Pharmacology
Case 2: Opioid Overdose
Clinical Scenario
A 28-year-old male is found unresponsive by EMS in a parking lot with drug paraphernalia nearby.
Patient Demographics
- Age: 28 years
- Sex: Male
- Weight: 70 kg (estimated)
Chief Complaint
Found unresponsive
History of Present Illness
EMS was called for an unresponsive male. Bystanders report the patient was seen injecting something into his arm before becoming unresponsive over approximately 5 minutes. A used syringe and small bags with white powder residue were found nearby. No medical history available.
Physical Examination
- Vital Signs: BP 85/52 mmHg, HR 52 bpm, RR 4 (shallow), T 35.6C, SpO2 78% on RA
- General: Unresponsive, cyanotic
- HEENT: Miosis (1 mm bilaterally, "pinpoint pupils")
- Respiratory: Severely diminished breath sounds, no chest wall movement
- Cardiovascular: Bradycardic, weak pulses
- Neurological: GCS 3 (no eye opening, no verbal, no motor response)
- Skin: Cool, mottled, injection sites on bilateral antecubital fossae
Prehospital Treatment
- Bag-mask ventilation initiated
- Intranasal naloxone 4 mg administered by EMS
- Patient began breathing spontaneously within 2 minutes
Workup and Results
| Test | Result | Reference Range |
|---|---|---|
| Urine drug screen | Positive for opiates, fentanyl | Negative |
| Blood glucose | 95 mg/dL | 70-100 mg/dL |
| Arterial blood gas | pH 7.18, PaCO2 72, PaO2 58 | - |
| Lactate | 4.8 mmol/L | 0.5-2.0 mmol/L |
Diagnosis
Opioid overdose - likely fentanyl/heroin mixture based on clinical presentation and drug screen
CNS Pharmacology Principles Illustrated
- Mu receptor effects: Opioids produce the classic triad of CNS depression, respiratory depression, and miosis through mu receptor activation.
- Respiratory depression mechanism: Opioids reduce brainstem sensitivity to CO2, causing hypoventilation.
- Naloxone mechanism: Competitive mu receptor antagonist that rapidly displaces opioids from receptors.
- Short duration of naloxone: Half-life 30-90 minutes, much shorter than most opioids - risk of re-sedation.
- Fentanyl potency: Synthetic opioid approximately 100x more potent than morphine, requiring higher naloxone doses.
Treatment
- Airway management: Bag-mask ventilation, consider intubation if no response to naloxone
- Naloxone: 0.4-2 mg IV/IM/IN, repeat every 2-3 minutes as needed
- Goal: Restore adequate respirations, not full consciousness
- Titrate to avoid precipitating severe withdrawal
- Continuous monitoring: High risk for re-sedation, especially with long-acting opioids or fentanyl analogs
- Naloxone infusion: Consider 2/3 of reversal dose per hour if repeated doses needed
- Observation: Minimum 4-6 hours; longer for extended-release opioids or methadone
- Addiction medicine consultation and harm reduction education
- Prescribe take-home naloxone upon discharge
Clinical Image
Various opioid medications. Opioid overdose has become a leading cause of death in young adults, with synthetic opioids like fentanyl increasingly implicated.
Image Source: Wikimedia Commons License: Public Domain URL: https://commons.wikimedia.org/wiki/File:Opioids.jpg