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IM22.1-13 | Poisoning — PBL Case

CLINICAL SETTING

It is a Saturday afternoon at the district general hospital emergency department in a small agricultural town in Telangana. Dr Anil, the on-call medical officer, and two final-year MBBS students — Kavitha and Rajan — are on duty when the ambulance radio crackles: 'Two patients incoming, same farmhouse. One adult male, estimated 45 years, found collapsed in the field near a pesticide drum. Second: adult female, 38 years, found in the kitchen — empty silver-grey tablet packet on the floor labelled 'Celphos.' ETA 8 minutes.' Kavitha opens the emergency logbook and writes: 'MLC 1: OP poisoning suspected. MLC 2: AlP poisoning suspected.' Dr Anil turns to the students: 'Before they arrive, tell me — what do you need to know, and what must be ready? What is different about these two cases?'

Trigger 1: Two Patients Arrive — Initial Assessment

Patient 1 (Gopal, 45 years): agricultural labourer, brought in by his son. Conscious but confused (GCS 11), excessive salivation and tearing, miosis bilaterally, diffuse wheeze on auscultation, HR 48/min, BP 90/60 mmHg, SpO2 82% on room air. His son reports he was found collapsed near a chlorpyrifos drum 45 minutes ago. His clothes are soaked and smell of pesticide. Patient 2 (Lakshmi, 38 years): brought in by her brother, found in the kitchen of the same farmhouse unconscious (GCS 5). BP 70/40 mmHg, HR 120/min, skin is cold and mottled. Her brother found an empty Celphos (aluminium phosphide) packet and a half-eaten roti on the kitchen floor. He says she had an argument with her husband earlier today. Dr Anil assigns Kavitha to Patient 1 and Rajan to Patient 2. He asks: 'Tell me the toxidrome for each patient and your immediate first three actions for each.'

DISCUSSION POINTS

  • Identify the toxidrome for each patient and explain the mechanism — how does OP poisoning produce miosis, bradycardia, and bronchospasm, and how does AlP poisoning produce cardiovascular collapse?
  • What are the first three concurrent actions for each patient, in order of priority? Specifically, for Patient 1: should atropine be given before or after the airway is managed?
  • Gopal's clothes are soaked in chlorpyrifos. What decontamination steps are required, and what precautions should the emergency team take to protect themselves?
Click to reveal Trigger 2: Antidote Decisions and a Drug Shortage (discuss previous trigger first!)

Trigger 2: Antidote Decisions and a Drug Shortage

Gopal (Patient 1) has been intubated, decontaminated, and given atropine 1.8 mg IV. Rajan reads from the notes that the chest is still wet with secretions and HR is still 48/min. Dr Anil says: 'Keep going — what is the titration endpoint?' Meanwhile, the pharmacist calls: 'We have pralidoxime 1 g ampoules, but only 2 ampoules in stock and the next supply is tomorrow.' Dr Anil adds: 'What is the role and the timing of pralidoxime? If we only have 2 g, what do we prioritise?' Across the resuscitation bay, Lakshmi is receiving IV noradrenaline. Her BP has partially responded to 0.3 mcg/kg/min — now 86/56 mmHg. Rajan's intern has prepared activated charcoal via nasogastric tube for Lakshmi as standard decontamination. Dr Anil sees this and stops the intern immediately. He turns to the students: 'Tell me exactly why we are NOT giving her activated charcoal or inserting an NG tube.'

DISCUSSION POINTS

  • What is the exact titration endpoint for atropine in OP poisoning, and what are the consequences of under-dosing versus over-dosing? How many milligrams might be needed in severe poisoning?
  • What is the mechanism of pralidoxime, what is the critical time window for it to be effective, and if limited to 2 g, how should it be administered?
  • Explain clearly why activated charcoal is contraindicated in aluminium phosphide poisoning — both in terms of efficacy and healthcare worker safety. What other common decontamination manoeuvres are also contraindicated and why?
Click to reveal Trigger 3: One Patient Improves; One Deteriorates (discuss previous trigger first!)

Trigger 3: One Patient Improves; One Deteriorates

Four hours later: Gopal (Patient 1) is stable on the ventilator. His chest has cleared significantly after a total of 12 mg of atropine. He is no longer wheezing. Dr Anil notes: 'Dry secretions — that is our endpoint.' Lakshmi (Patient 2) has deteriorated despite escalating vasopressors (noradrenaline 1.2 mcg/kg/min + adrenaline 0.5 mcg/kg/min). Her BP is 60/35 mmHg. Her ECG shows widening QRS. The family is gathered in the waiting area — Lakshmi's husband, her elderly mother, and her brother. The brother says loudly: 'She must have been poisoned by someone — she was fine this morning.' Dr Anil asks Rajan: 'Walk me through what you must do now in terms of medico-legal obligations, and how do you approach the family?'

DISCUSSION POINTS

  • Both patients have been registered as medico-legal cases. What are the specific medico-legal obligations at this point — what must the doctor record, report, and not record in the MLR?
  • The brother alleges homicidal intent. How should the medical team respond to this allegation — what is documented, what is NOT documented, and who has the authority to investigate intent?
  • How do you counsel Lakshmi's family about her prognosis? Draft a 3-4 sentence honest statement that acknowledges the gravity of the situation without offering false hope.
Click to reveal Trigger 4: Day 10: An Unexpected Complication and a Late Admission (discuss previous trigger first!)

Trigger 4: Day 10: An Unexpected Complication and a Late Admission

Gopal has been weaned off the ventilator on day 3 and transferred to the ward. On day 10, the ward nurse calls urgently: Gopal has developed sudden proximal limb weakness, cannot raise his arms or lift his head off the pillow, and his deep tendon reflexes are absent. He was eating well yesterday and had no cholinergic symptoms. Meanwhile, a new patient arrives: a 28-year-old man, Prakash, who ingested illicit hooch at a wedding 14 hours ago. He complains of 'vision going dark,' severe headache, and confusion. Blood gas: pH 7.14, bicarbonate 6 mmol/L, high anion gap. Osmolar gap on admission: 42 mOsm/kg (normal <10). Dr Anil asks Kavitha: 'Name the complication in Gopal and its mechanism. For Prakash — what is the diagnosis, what metabolite is causing the visual loss, and what are your treatment priorities?'

DISCUSSION POINTS

  • What complication has Gopal developed, at what typical time window does it occur, and what is its pathophysiology? How does this differ from organophosphate-induced delayed polyneuropathy (OPIDP)?
  • Prakash has a high osmolar gap and high anion gap metabolic acidosis with visual symptoms. Which toxic alcohol is most likely, and what is the toxic metabolite responsible for optic nerve damage?
  • The hospital formulary does not have fomepizole. What is the alternative ADH inhibitor, how is it administered, and when is haemodialysis mandatory in Prakash's case?

Group Task Assignments

  • Construct a one-page Emergency Department Poisoning Protocol for a district hospital managing both OP and AlP poisoning simultaneously, covering: triage priorities, decontamination steps and worker precautions, antidote availability checklist (atropine, pralidoxime, naloxone, fomepizole/ethanol), and contraindicated interventions for each toxin.
  • Prepare the medico-legal report (MLR) template for Lakshmi's case. Include: MLC number, date/time of examination, history as received, clinical findings, investigations, treatment given. Discuss what is explicitly NOT included regarding suicidal/homicidal intent.
  • Design a family counselling guide for the management of a patient with aluminium phosphide poisoning in an Indian district hospital: what to tell the family at admission, during the critical first 12 hours, and if the patient deteriorates. Include honest prognostic language.
  • Compare the management of methanol and ethylene glycol poisoning in a table: source, toxic metabolite, target organ toxicity, specific diagnostic clue (urine finding or symptom), treatment with fomepizole vs ethanol, and indication for haemodialysis.

Learning Issues

Research these questions and bring your findings to the discussion.

  1. [IM22.1] What is the ABC-based initial stabilisation approach for any poisoned patient, and how does the presence of a toxidrome modify the resuscitation sequence?
  2. [IM22.5] What are the five major toxidromes (cholinergic, anticholinergic, opioid, sympathomimetic, serotonin), and what is the distinguishing clinical feature of each?
  3. [IM22.6] What is the complete management protocol for organophosphate poisoning — atropine titration endpoint, pralidoxime mechanism and timing, and complications (intermediate syndrome, OPIDP)?
  4. [IM22.7] Why is aluminium phosphide poisoning essentially untreatable with specific antidotes, and what supportive care measures are used? What interventions are explicitly contraindicated?
  5. [IM22.8] How does the management of methanol and ethylene glycol poisoning differ, and when is haemodialysis mandatory for each?
  6. [IM22.10] What are the medico-legal obligations of the treating physician in a poisoning case in India, and what is the distinction between clinical documentation and determination of intent?
  7. [IM22.12] What are the key principles of family counselling when the treating physician must communicate a grave prognosis — including when there is no antidote?