OP / Carbamate Poisoning Management Protocol
Complete treatment protocol with therapeutic guidelines and monitoring.
- OP compounds inhibit acetylcholinesterase (AChE) leads to the accumulation of acetylcholine at cholinergic synapses.
- OP poisoning diagnosed by a good history of acute exposure and development of characteristic clinical effects (box 1) Onset of clinical toxicity is variable; however most patients who will develop severe toxicity usually have symptoms within 6h.
- Quantification of butyrylcholinesterase or acetylcholinesterase activity is helpful in diagnosis and followup.
Box (1) Clinical features of acute OP poisoning
Muscarinic (DUMBELS): diarrhoea, urinary frequency, miosis, bradycardia, bronchorrhoea and bronchoconstriction, emesis, lacrimation, salivation, and hypotension.
Nicotinic: fasciculations and muscle weakness, paralysis and respiratory failure, mydriasis, tachycardia, and hypertension.
Central nervous system: altered level of consciousness, respiratory failure, and seizures.
Box (2) WHO classification for OP toxicity
Mild: subjective weakness, fasciculations of the tongue and eyelids, miosis, vomiting, sweating.
Moderate: salivation, bronchorrhoea, lachrymation, abdominal cramps, diarrhoea, hypertension and generalized muscular fasciculations.
Severe:
- Respiratory depression, pulmonary oedema, cyanosis, loss of sphincter control, coma, convulsions.
- Hypotension, bradycardia or tachycardia, cardiac ischemia, cardiac dysrhythmia.
- Hypokalemia and hyperglycaemia.
- Acute pancreatitis has also been observed.
ICU Management
- Regular review of respiratory function, Intubate and ventilate if needed.
- ECG, CXR for monitoring cardiac and respiratory complications.
- Serial monitoring: AChE, Na, K, RBS, ABG, KFT, LFT every 24 hr.
- Urinary catheterization for moderate and severe cases.
- Seizures → Diazepam 10 mg IV, repeatable.
- Vasopressors (dopamine, levophed) if hypotension unresponsive to fluids and atropine.
- MgSO4: for ventricular arrhythmia or hypomagnesemia.
- Assess flexor neck strength to detect intermediate syndrome.
- Discharge when stable, asymptomatic, not requiring oximes or atropine for 1 day.
Atropine Therapy
| Age group | Initial dose | Repeat | Maintenance |
|---|---|---|---|
| Adults | 1–2 mg IV every 5–10 min | Until atropinization (clear chest, HR > 80, SBP > 80) | 10–20% of total loading dose / hour IV infusion |
| Children | 0.02–0.05 mg/kg IV every 5–10 min | Until atropinization | 10–20% of total loading dose / hour IV infusion |
⚠ Pupil size is not a target.
Large doses may be required (hundreds of mg per day).
Signs of atropinization: clear chest, HR > 80/min, SBP > 80 mmHg, dry skin, adequate perfusion.
Signs of toxicity: agitation, hyperthermia, urinary retention, absent bowel sounds.
Oximes Therapy
| Drug | Loading dose | Infusion | Notes |
|---|---|---|---|
| Obidoxime | 250 mg IV slowly over 5 min (repeat if needed) | 750 mg / day IV infusion | Do not exceed recommended doses. |
| Pralidoxime | 30 mg/kg IV over 10–20 min | 8–10 mg/kg/h IV infusion | High doses may cause HTN & arrhythmias. |
Best effect when given early before aging of AChE enzyme.
Complications & Monitoring
- Respiratory failure → may require intubation & ventilation.
- Convulsions: treat with diazepam 0.1–0.3 mg/kg IV (max 10 mg/dose).
- Arrhythmias: continuous ECG monitoring.
- Electrolytes & fluids: correct promptly.
Monitoring Schedule
| Parameter | Frequency | Notes |
|---|---|---|
| Vital signs | Every 30–60 min → then q2–4h | Continuous SpO₂ in ICU |
| Neurological status | Hourly | Watch for seizures & toxicity |
| Chest auscultation | Every 2–4 h | Check secretions / wheeze |
| ECG | Continuous in severe cases | Arrhythmias common |
| ABG | Every 6–8 h or if deterioration | Adjust ventilation |
| Electrolytes / RBS | q12–24 h | Correct abnormalities |
| Renal function | Daily | Especially with oximes |
| Pseudocholinesterase | Baseline + q24–48 h | For follow-up, not acute |
