Exposure to organophosphates may occur via cutaneous, oral or inhalational routes. The sources of organophosphates are listed below. SIGNS AND SYMPTOMS Check for the characteristic garlic-like or petroleum odor. The onset of symptoms varies depending on the route of exposure, the amount and the type of organophosphate. CVS: Bradycardia and hypotension (muscarinic) or tachycardia and hypertension (nicotinic). Respiratory: Cough, rhinorrhea, bronchorrhea, bronchoconstriction and respiratory/diaphragmatic paralysis. GI and urinary: Hypersalivation, nausea, vomiting, abdominal pain, diarrhea, fecal incontinence, and urinary incontinence. Ocular: Blurred vision, excessive lacrimation, miosis (muscarinic) or mydriasis (nicotinic). Cutaneous: Diaphoresis Musculoskeletal: Fasciculations, cramping, weakness and diaphragmatic paralysis. CNS: Anxiety, emotional lability, restlessness, confusion, ataxia, tremors, seizures, and coma. Intermediate syndrome: Seen in ~20% of the patients. It is characterized by weakness of neck flexion, decreased DTRs, cranial nerve abnormalities, proximal muscle weakness and respiratory insufficiency. Exposure to a highly lipid soluble organophosphate and an inadequate dose of oximes are risk factors for the development intermediate syndrome. The incidence of intermediate syndrome following carbamate exposure is low. INVESTIGATIONS Diagnosis is based on clinical findings. Cholinesterase levels Plasma Acetylcholinesterase (RBC) Depressed levels generally indicate exposure. Most helpful if the patient had a pre-exposure baseline measurement for comparison. Draw blood for measurement of RBC and plasma cholinesterase levels prior to treatment with pralidoxime (2-PAM). Serial monitoring of the levels can be used to determine response to therapy. Plasma Pseudocholinesterase Is a more sensitive indicator of exposure but is not as specific as AChE activity. it does not correlate as well as plasma acetylcholinesterase with the severity of poisoning. Other investigations Electrolytes ABG Serum glucose BUN, Serum creatinine LFT ECG monitoring and Troponins Sinus tachycardia is the most common finding. Sinus bradycardia with PR prolongation can develop with increasing toxicity. May find prolonged QTc interval, elevated ST segments, and inverted T waves. Troponins may be elevated. A chest x-ray is done if pulmonary edema or aspiration of a hydrocarbon solvent is suspected. Atropine challenge: can be done when the diagnosis is in doubt. Atropine 1 mg IV in adults or 0.01-0.02 mg/kg in children is administered. The absence of anticholinergic signs (tachycardia, mydriasis, decreased bowel sounds, dry skin) strongly suggests poisoning with organophosphate or carbamate. MANAGEMENT Ensure airway, breathing and circulation Start supplemental oxygen and intubate the patient if needed. Warning: Do not use succinylcholine during intubation as it is degraded by plasma cholinesterase and may result in prolonged paralysis. Do not perform mouth to mouth resuscitation as there is a risk of contamination. Start iv fluids. Decontamination Remove all clothing and gently cleanse patients with soap and water. Ocular irritation if indicated. Gastric lavage may be done if the patient presents within 30 min of ingestion and the patient is intubated with the airway protected. Activated charcoal is given when the patient presents within 1 hr of ingestion and the airway is protected. Dose 50g or 1g/kg Atropine Dose: Adults: 2-5 mg IV, Children: 0.02-0.05 mg/kg IV Double the dose every 3-5 min. till atropinization. A patient is considered to be atropinized when the bronchial secretions are dry, O2 are normal, heart rate >80 bpm and BP > 80 mmHg. Once the patient is stable start atropine infusion. Dose:start the infusion with 10% to 20% of the initial atropinization dose per hour. The duration of atropine therapy depends on the severity and response to treatment. Usually, the infusion is maintained for 24 to 48 hrs and withdrawn gradually over the next 3-5 days depending on the response. Pralidoxime (2-PAM) There are no guidelines for the administration of pralidoxime. In general, the benefit is the highest when given early. Initial dose: Adults: 1 to 2g (30 mg/kg) of 2-PAM in 100 mL NS IV administered slowly over 20-30 minutes. Children: 25-50 mg/kg in 100 mL NS IV administered slowly over 20-30 minutes. Maintenance dose: Adults: 500mg/hr OR 8mg/kg/hr IV. Children: 10-20 mg/kg/hr IV. The infusion should be continued until the patient remains symptom-free for at least 12 hours without additional atropine doses OR until the patient is extubated. Seizures: Diazepam 10mg IV (0.1 to 0.2 mg/kg in children), can be repeated of needed. Do not use phenytoin. Torsades de pointes should be treated in the standard manner. IV magnesium sulfate has been reported to be beneficial.
