-OP compounds are widely used as pesticides, for eradication of vectors.
Malathion,Fenthion,Methamidophos,Diazinon,Chlorpyrifos,Parathion are the common insecticides.
- Acute cholinergic syndrome:- occur within minutes of exposure.
- Pungent garlic like odour in breath, vomit and clothing; Muscarinic effects -miosis , bronchorrhoea, bronchospasm, salivation , lacrimation , abdominal pain , bradycardia
- Nicotinic effects- Muscle fasciculation, hyper-reflexia, flaccid muscle weakness with reduced tendon reflexes
- CNS effects- headache, dizziness, confusion, drowsiness, coma , fits , central respiratory depression
- The Intermediate Syndrome- begins 48hrs after poisoning but may be delayed for 72-96 hrs. Follows resolution of the acute phase , in some instances occurs while symptoms of acute phase are still present.
- Muscle weakness causing respiratory distress and failure; progression of muscle weakness from ocular muscles to the neck and proximal limbs to the respiratory muscles.
Organophosphate induced delayed polyneuropathy:-
Occurs 1-3 weeks after acute exposure due to degeneration of long myelinated nerve fibres. Cramping muscle pains in the legs , numbnesss and paraesthesiae in the distal upper and lower limbs, shuffling gait , wrist drop.
Muscle wasting and deformity, symmetrical flaccid weakness of distal limbs, tendon reflexes reduced or lost, absent ankle reflexes.
-Removal from site of exposure and of contaminated clothing and contact lenses.
-airway cleared and high flow oxygen administered.
-skin washed with soap and water and eyes irrigated.
-gastric lavage within an hour of ingestion by KMNO4 via nasogastric tube after establishing intravenous access and airway protection.
-Atropine : 1.8-3mg bolus immediately.
Double the dose every 5mins until atropinised- dilated pupil, clear lungs, dry tongue, normal heart rate and BP.
Heart rate maintain 110-120/min not<90.
Once patient is atropinised give 20-30% dose required for atropinisation as infusion/hr.
Eg: 15ml for atropinisation ( 1ml=0.6mg) then maintain at 20% dose of atropinisation at 1 hr i.e 3ml
Total dose = 3ml x 24 hr= 72ml
In 1 pint put 15ml of atropine and as muscarinic effect decreases decrease dose i.e 8ml-6ml-4ml-2ml
-Oximes : Pralidoxime 1g bolus in 30 mins then infusion 0.5g/hr
Pralidoxime 1g in 100ml NS drip in 30 mins stat then TDS for 5 days.
Or , Obidoxime 0.25mg bolus then infusion 0.75g/24hrs.
Convulsions are controlled with I.V. Diazepam.
Monitoring of ECG, blood gases, temperature, urea and electrolytes , amylase and glucose is mandatory.
OP poisoning cases should be always kept under observation in Intensive Care Unit for 5-6 days.
– Dr. Mahesh Shrestha