Organophosphate Poisoning

An organophosphate is a chemical compound used by both the industrial and residential sectors. These compounds are wildly used as insecticides as well as in ophthalmic agents and anthelmintic agents. They’re the prime choice for insecticides because of their ability to inhibit acetylcholinesterase (AChE). The AChE enzyme is responsible for breaking down the neurotransmitter acetylcholine (ACh) into choline and acetic acid, which is found in the neuromuscular junctions, the central and peripheral nervous systems as well in red blood cells and serves as a chemical messenger for many different functions (e.g. the contraction of skeletal muscles and also inhibits the activation of the cholinergic system). By inhibiting this enzyme, the ACh accumulates throughout the nervous system which causes a collection of symptom that can be categorized into three categories; 1) Muscarinic symptoms 2) Nicotinic symptoms and 3) CNS symptoms.

In this particular case, the patient was presenting with symptoms in all three categories. Muscarinic effects can be remembered using the acronyms SLUDGE and DUMBELS.

SLUDGE (Saliva, Lacrimation, Urination, GI Upset, and Emesis)

DUMBBELS (Diaphoresis and Diarrhea, Urination, Miosis/Muscle weakness, Bronchorrhea, Bradycardia, Emesis, Lacrimation, Salivation/Sweating)

Our patient was presenting with increase lacrimation which was noted as “crying”, emesis was also found on her shirt and shoes as well as diaphoresis and bronchospasms noted as the audible wheezing and the dyspnea.

Nicotinic effects manifest as autonomic nervous system symptoms such as; hypertension, tachycardia, and pallor as well as any symptoms related to inappropriate activation of skeletal muscles. These usually manifest as muscle twitches (fasciculations), cramping and weakness. If we recall, our patient had apparent facial fasciculations seen by our bystander as “weird twitching” in her face.

Central nervous system (CNS) signs and symptoms can manifest as; confusion, anxiety, restlessness, ataxia, and tremors. Our patient was presenting with confusion and sporadic walking.

An interesting characteristic about OP poisoning is that patients may present with the smell of garlic or petroleum which can be helpful in confirming the diagnostic.

The treatment of choice for a severe organophosphate poisoning is Atropine. Atropine will relieve bronchospasms (see in this patient by the audible wheezing and SOB) given at 2 to 5 mg IV dose which can be doubled q. 3 to 5 minutes prn. Atropine is followed by Pralidoxime which will relieve neuromuscular (nicotinic) symptoms (seen in this patient by facial fasciculations) given at a dose of 1 to 2 g over a period of 15 to 30 minutes IV, a bolus can also be given afterward.