Organophosphate toxicity: Difference between revisions
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**Ventricular dysrhytmias, torsades, QT prolongation, AV block | **Ventricular dysrhytmias, torsades, QT prolongation, AV block | ||
{{Cholinergic Toxicity Treatment}} | |||
==Disposition== | ==Disposition== | ||
Revision as of 01:48, 12 June 2014
Background
- Irreversibly binds acetylcholinesterase -> cholinergic crisis
- Used as insecticides (malathion) and chemical warfare (sarin, VX)
- Consider in ddx of pt w/ AMS + miotic pupils
Clinical Features
- SLUDGE(MM)
- Salivation, lacrimation, urination, diarrhea, GI pain, emesis, miosis, muscle weakness
- Killers B's
- Bradycardia, bronchorrhea, bronchospasm
Diagnosis
- CBC
- May show leukocytosis
- Lipase
- LFT
- CXR
- Pulmonary edema in severe cases
- ECG
- Ventricular dysrhytmias, torsades, QT prolongation, AV block
Decontamination
- Providers should wear appropriate PPE during decontamination.
- Neoprene or nitrile gloves and gown (latex and vinyl are ineffective)
- Dispose of all clothes in biohazard container
- Wash patient with soap and water
Supportive Care
- IVF, O2, Monitor
- Aggressive airway management is of utmost importance.
- Intubation often needed due to significant respiratory secretions / bronchospasm.
- Use nondepolarizing agent (Rocuronium or Vecuronium)
- Succinylcholine is absolutely contraindicated
- Benzodiazepines for seizures
Antidotes
- Dosing with atropine and pralidoxime are time dependent and provides ability to reverse symptoms while awaiting agent metabolism
- For exposure to nerve agents, manufactured IM autoinjectors are available for rapid administration:
- Mark 1
- Contains 2 separate cartridges: atropine 2 mg + 2-PAM 600 mg
- Being phased out with newer kits
- DuoDote
- Single autoinjector containing both medications
- Same doses as Mark 1: atropine 2 mg + 2-PAM 600 mg
- Mark 1
Antidotes
Atropine
- Competitively blocks muscarinic sites (does nothing for nicotinic-related muscle paralysis)
- May require massive dosage (hundreds of milligrams)
- Dosing[1]
- Adult: Initial bolus of 2-6mg IV; titrate by doubling dose q5-30m until tracheobronchial secretions controlled
- Once secretions controlled → start IV gtt 0.02-0.08 mg/kg/hr
- Child: 0.05-0.1mg/kg (at least 0.1mg) IV; repeat bolus q2-30m until tracheobronchial secretions controlled
- Once secretions controlled → start IV gtt 0.025 mg/kg/hr
- No max dose, doses >400mg have been reported[2]
Pralidoxime
- AKA 2-PAM
- For Organophosphate poisoning only - reactivates AChE by removing phosphate group → oxime-OP complex then excreted by kidneys.
- This must be done before "aging" occurs - conformational change that makes OP bond to AChE irreversible[3]
- Pralidoxime can actually bind and inhibit AChE once all AChE enzymes have aged, and can make the toxicity worse
- Window to aging depends on the agent, and is a matter of debate, but pralidoxime within 1-2 hours of exposure is the goal
- Dosing[1]
- Adult: 1-2gm IV over 15-30min; repeat in 1 hour if needed or 50 mg/hr infusion.
- Child: 20-40mg/kg IV over 20min; repeat in 1 hour if needed or 10-20 mg/kg/hr infusion.
Disposition
- Minimal exposure only requires decon and 6-8hr obs
See Also
Source
- Tintinalli
- ↑ 1.0 1.1 Agency for Toxic Substances and Disease Registry, Case Studies in Environmental Medicine, Cholinesterase Inhibitors: Including Pesticides and Chemical Warfare Nerve Agents. Centers for Disease Control (CDC). PDF Accessed 06/21/15
- ↑ Hopmann G, Wanke H. Höchstdosierte Atropinbehandlung bei schwerer Alkylphosphatvergiftung [Maximum dose atropin treatment in severe organophosphate poisoning (author's transl)]. Dtsch Med Wochenschr. 1974;99(42):2106-2108. doi:10.1055/s-0028-1108097
- ↑ Eddleston M, Szinicz L, Eyer P, Buckley, N (2002) Oximes in Acute Organophosphate Pesticide Poisoning: a Systematic Review of Clinical Trials. QJM. 95(5): 275–283.