Pharmacology · Year 2 · from Pharmacology
Case 1: Organophosphate Poisoning (Cholinergic Toxidrome)
Clinical Scenario
A 42-year-old male farm worker is brought to the emergency department after collapsing in a field where he was spraying pesticides.
Patient Demographics
- Age: 42 years
- Sex: Male
- Weight: 75 kg
Chief Complaint
Found unresponsive with excessive secretions and difficulty breathing
History of Present Illness
The patient was spraying organophosphate insecticides without proper protective equipment when he developed progressive weakness, blurred vision, and abdominal cramping. Coworkers found him collapsed with profuse salivation, labored breathing, and urinary incontinence approximately 30 minutes later. EMS noted pinpoint pupils and wheezing on arrival.
Physical Examination
- Vital Signs: BP 90/60 mmHg, HR 48 bpm, RR 28 (labored), T 36.2C, SpO2 82% on room air
- General: Obtunded, copious oral secretions, incontinent of urine
- HEENT: Miosis (1 mm pupils bilaterally), profuse lacrimation and salivation
- Respiratory: Diffuse wheezes and rhonchi, bronchorrhea
- Cardiovascular: Bradycardic, regular
- Abdominal: Hyperactive bowel sounds, involuntary defecation
- Neurological: Obtunded, fasciculations visible in all extremities
- Skin: Profuse diaphoresis
Workup and Results
| Test | Result | Reference Range |
|---|---|---|
| Red blood cell cholinesterase | 15% of normal | 80-120% |
| Plasma pseudocholinesterase | 800 U/L | 4,000-12,000 U/L |
| Arterial blood gas | pH 7.28, PaCO2 55, PaO2 58, HCO3 22 | - |
| Glucose | 165 mg/dL | 70-100 mg/dL |
| Potassium | 3.2 mEq/L | 3.5-5.0 mEq/L |
Diagnosis
Organophosphate poisoning presenting with SLUDGE/BBB syndrome (cholinergic toxidrome)
Autonomic Pharmacology Principles Illustrated
- Acetylcholinesterase inhibition: Organophosphates irreversibly inhibit AChE, causing acetylcholine accumulation at all cholinergic synapses.
- SLUDGE mnemonic: Salivation, Lacrimation, Urination, Defecation, GI distress, Emesis - all muscarinic effects.
- Nicotinic effects: Muscle fasciculations and eventual paralysis (neuromuscular junction), plus variable autonomic effects.
- Bradycardia: Muscarinic M2 receptor overstimulation in the heart.
- Bronchospasm and secretions: M3 receptor stimulation - most life-threatening effects.
Treatment
- Decontamination: Remove clothing, wash skin thoroughly
- Airway management: Intubation with succinylcholine alternatives (prolonged paralysis risk)
- Atropine: 2-4 mg IV bolus, double dose every 5 minutes until secretions dry (may need 100+ mg)
- Pralidoxime (2-PAM): 1-2 g IV over 30 minutes within 24-48 hours to reactivate AChE before "aging"
- Benzodiazepines: Diazepam 10 mg IV for seizures
- ICU admission for respiratory support and monitoring
Clinical Image
Miosis (pinpoint pupils) as seen in cholinergic toxicity from organophosphate poisoning. Pupillary constriction results from muscarinic receptor stimulation of the pupillary sphincter muscle.
Image Source: Wikimedia Commons License: CC BY 2.0 URL: https://commons.wikimedia.org/wiki/File:Miosis.jpg