Answer: Acute Opioid (Heroin/Morphine) Poisoning

a) Probable Diagnosis & Bedside Confirmatory Test (2 marks)

• Found unconscious with empty vials and syringes - intravenous drug use
• Pinpoint (miotic) pupils bilaterally - hallmark of opioid toxidrome
• Hypotension (BP 90/60 mmHg) and bradypnea (respiratory rate 15/min, but noted as severe respiratory depression)
• Frothy secretions around mouth and nostrils - pulmonary edema from opioid-induced respiratory depression
• Tattoos masking venepuncture marks, and multiple pustule-like lesions (skin popping abscesses) on arms and groin - classic signs of chronic IV drug abuse

• A rapid urine drug screen (immunochromatographic strip test) at the bedside will confirm the presence of opioids/morphine/heroin metabolites (6-monoacetylmorphine, morphine glucuronide) within minutes.
• Alternatively, the diagnosis can also be confirmed by the dramatic response to IV Naloxone (0.4-2 mg IV) - reversal of miosis and improved respiratory rate is both diagnostic and therapeutic ("therapeutic trial").

b) Mechanism of Action of Heroin/Opioids (3 marks)

1. Opioid Receptors: Opioids act on specific G-protein-coupled receptors (GPCRs):
   • Mu (μ) receptors - primary mediators of analgesia, euphoria, respiratory depression, miosis, reduced GI motility, and physical dependence
   • Kappa (κ) receptors - spinal analgesia, sedation, miosis, dysphoria
   • Delta (δ) receptors - analgesia, modulation of mu-receptor activity
2. Intracellular signaling: Opioid receptor activation inhibits adenylate cyclase (reducing cAMP), opens K⁺ channels (hyperpolarization of neurons), and closes voltage-gated Ca²⁺ channels - collectively reducing neuronal excitability and neurotransmitter release.
3. CNS effects relevant to this case:
   • Respiratory depression: Direct action on the pre-Botzinger complex in the brainstem, reducing respiratory rate and tidal volume - leads to hypoxia, pulmonary edema, and frothy secretions
   • Miosis: Stimulation of the Edinger-Westphal nucleus (parasympathetic oculomotor) - causes pinpoint pupils even in coma
   • Hypotension: Peripheral vasodilation + histamine release + decreased sympathetic outflow
4. Heroin's specific advantage for abusers: High lipid solubility means it crosses the blood-brain barrier very rapidly (within seconds of IV injection), producing an intense "rush" of euphoria before conversion to morphine.

c) Management (7 marks)

• Airway: Position the patient (recovery/left lateral), clear secretions, insert oropharyngeal airway
• Breathing: Administer 100% O₂ via face mask; if respiratory rate remains inadequate, prepare for endotracheal intubation and mechanical ventilation
• Circulation: IV access × 2 large-bore cannulae; IV fluids (normal saline) for hypotension; cardiac monitoring and pulse oximetry

• Naloxone 0.4-2 mg IV (pure competitive opioid antagonist at all opioid receptors) - administer immediately
• Onset within 1-2 minutes; reverses respiratory depression, miosis, and altered consciousness
• Repeat every 2-3 minutes up to a total dose of 10 mg if no response
• Since heroin's duration of action exceeds naloxone's (naloxone half-life ~60-90 min vs. heroin effect several hours), a continuous IV infusion of naloxone (2/3 of the effective bolus dose per hour) is necessary to prevent re-narcotization
• Monitor closely - abrupt reversal may precipitate acute withdrawal (agitation, tachycardia, vomiting, seizures)

• Pulmonary edema management: Elevate head-end of bed, positive pressure ventilation if needed; avoid diuretics (not cardiogenic)
• Seizures: IV benzodiazepines (diazepam 5-10 mg IV)
• Hypotension: IV crystalloid infusion; vasopressors (noradrenaline) if refractory
• Hypoglycemia exclusion: Immediate fingerstick glucose; give 50% dextrose if hypoglycemic (also consider IV thiamine if alcoholism co-suspected)

• Gastric lavage is NOT indicated for IV drug use
• If oral ingestion suspected: activated charcoal (1 g/kg) may be given if airway is protected

• The pustule-like lesions indicate skin-popping abscesses - wound care, send swabs for C&S, broad-spectrum antibiotics (e.g., amoxicillin-clavulanate or clindamycin) to cover Staph. aureus (including MRSA)
• Screen for HIV, Hepatitis B and C, infective endocarditis (common co-morbidities in IV drug users)
• Rhabdomyolysis: Check CK, urine myoglobin; IV hydration

• ICU admission with continuous monitoring for at least 24 hours
• Repeat naloxone doses as needed
• Psychiatric evaluation and referral to drug de-addiction program once medically stable
• Notify medico-legal authorities (police) as this is a medico-legal case

d) Autopsy Samples and Preservatives (In Case of Death) (3 marks)

• Saturated NaCl (common salt) solution is the standard preservative for visceral organs in Indian forensic practice (prevents putrefaction without interfering with chemical analysis). Rectified spirit (alcohol) is specifically AVOIDED in cases of suspected poisoning with volatile substances or alcohol, but also generally avoided in drug cases as it may extract or dissolve certain substances.
• For blood samples, sodium fluoride (inhibits glycolysis and bacterial enzyme activity) is preferred.
• Vitreous humor is particularly valuable in opioid deaths because it is protected from putrefaction and systemic redistribution, providing reliable drug concentrations even when the body is decomposed.
• Each specimen is placed in a separate, clean, sealed glass container, labeled, and sent to the Forensic Science Laboratory under chain of custody (sealed with magistrate's seal in India).

• Classic triad of opioid overdose: Coma + Pinpoint pupils + Respiratory depression ("opioid toxidrome")
• Bedside test: Urine immunoassay OR naloxone therapeutic trial
• Antidote: Naloxone (competitive opioid antagonist) - repeat dosing and infusion required
• Forensic samples: viscera in saturated NaCl, blood in sodium fluoride/oxalate, vitreous humor without preservative