Organophosphate Poisoning in a District Hospital
A 34-year-old male farmer from Nueva Ecija, weighing 60 kg, is brought to a district hospital 2 hours after spraying chlorpyrifos without PPE. He has profuse salivation, lacrimation, urination, diarrhea, vomiting, bradycardia (48/min), miosis, generalized fasciculations, bronchorrhea, and oxygen saturation 88% on room air. The emergency physician gives atropine 2 mg IV, then 1 mg IV every 5 minutes for two doses. The patient remains wheezing with crackles and a heart rate of 56/min. The hospital stocks atropine 1 mg/mL in 1 mL ampules, but pralidoxime is not available. The nearest tertiary hospital with ICU and pralidoxime is 2 hours away by ambulance. The pharmacist is asked to advise on atropine dosing, the role of pralidoxime, and drugs to avoid.
1. Assess whether the patient is adequately atropinized and recommend the next atropine dose and route.
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The patient is not adequately atropinized. Endpoints are drying of bronchial secretions and skin, heart rate above 80–100/min, and improved oxygenation-not pupil size. The current 1 mg every 5 minutes is too small for severe organophosphate poisoning. For a 60-kg adult with severe poisoning, give atropine 2–5 mg IV, then double the dose every 3–5 minutes until secretions clear and heart rate rises; then start an infusion of about 0.02–0.05 mg/kg/h (or 10–20% of the total loading dose per hour) and titrate. The next dose here could be 4 mg IV with reassessment in 3–5 minutes. Suction secretions, give oxygen, and prepare for intubation; atropine without airway support is not enough.
2. Explain the role and timing of pralidoxime and whether transfer is justified.
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Pralidoxime reactivates acetylcholinesterase if given before enzyme aging; it is most useful early, especially with continuing absorption. Give a loading dose of 30 mg/kg IV over 30 minutes (or 1–2 g), then 8–10 mg/kg/h, if it can be obtained. Because the hospital has none and the referral is 2 hours away, stabilize with atropine and airway care first, then transfer to the tertiary hospital; do not delay transfer for a dose that is not on hand. If pralidoxime arrives before departure, give the loading dose and arrange continuation. Monitor for intermediate syndrome (weakness of neck flexors and respiratory muscles) and for seizures.
3. Which drugs should be avoided and why?
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Avoid succinylcholine for intubation: pseudocholinesterase is inhibited, so paralysis may be prolonged. Avoid morphine and other respiratory depressants because bronchorrhea and respiratory failure are already present. Use benzodiazepines for seizures, not morphine. Also avoid mouth-to-mouth without barrier protection and ensure staff decontamination; remove contaminated clothing and wash skin. Atropine and pralidoxime are the specific treatments.