Organic Phosphorous Compound and Carbamate Toxicity Clinical Presentation

Updated: Dec 29, 2016
  • Author: Daniel K Nishijima, MD, MAS; Chief Editor: Asim Tarabar, MD  more...
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Presentation

History

Patients with organophosphorous compound (OPC) or carbamate toxicity usually have a history of exposure, either suicidal or unintentional. Pesticides can rapidly be absorbed through the skin, lungs, gastrointestinal (GI) tract, and mucous membranes. The rate of absorption depends on the route of absorption and the type of OPC or carbamate. Symptoms usually occur within a few hours after GI ingestion and appear almost immediately after inhalational exposure.

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Physical Examination

In the Tokyo sarin attack, miosis was the most common (>90%) indicator of OP poisoning. [10] Bradycardia is not a reliable finding, and patients may be tachycardic, for 2 reasons: First, hypoxia due to bronchorrhea and bronchospasm can lead to sympathetic outflow, which overrides parasympathetic vagal stimulation of the heart and which causes tachycardia. Second, nicotinic acetylcholine (ACh) receptors are present in both sympathetic and parasympathetic ganglia. These ganglionic effects in the sympathetic system may contribute to tachycardia.

Patients often present with evidence of a cholinergic toxic syndrome, or toxidrome. It is useful to remember the toxidrome in terms of the following 3 clinical effects on nerve endings:

  • Nicotinic effects at neuromuscular junctions and autonomic ganglia
  • Central nervous system (CNS) effects
  • Muscarinic effects.

Nicotinic signs and symptoms include weakness, fasciculations, and paralysis, whereas CNS effects may lead to seizures and CNS depression. Two common mnemonics to remember the muscarinic signs and symptoms of the cholinergic toxidrome are SLUDGE/BBB and DUMBELS. The SLUDGE/BBB mnemonic is as follows:

  • S = Salivation
  • L = Lacrimation
  • U = Urination
  • D = Defecation
  • G = GI symptoms
  • E = Emesis
  • B = Bronchorrhea
  • B = Bronchospasm
  • B = Bradycardia

The DUMBELS mnemonic is as follows:

  • D = Diarrhea and diaphoresis
  • U = Urination
  • M = Miosis
  • B = Bronchorrhea, bronchospasm, and bradycardia
  • E = Emesis
  • L = Lacrimation
  • S = Salivation
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Causes

Agricultural exposure is the most common cause of OPC and carbamate poisoning. The World Health Organization (WHO) classifies these poisonings as class I (extremely toxic) to class III (slightly hazardous). The WHO advocates banning or strong restrictions on the use of class I pesticides and a reduction in the use of pesticides to a minimal number of compounds that are less hazardous than others. [11]  However, a 2-year longitudinal study comparing cholinesterase activity levels and depressions in farmworkers and non-farmworkers, found that the farmworkers had significantly greater likelihood of cholinesterase depression across the agricultural season. The researchers called into question the effectiveness of current regulations designed to prevent pesticide exposure. [12]

OPCs may also be encountered in the military setting or as the result of a terrorist attack with nerve agents such as sarin, VX, or soman.

In addition to their use as insecticides, carbamates are used to treat certain medical diseases, such as glaucoma and myasthenia gravis (neostigmine, physostigmine). Some case reports describe clinical illness from foodborne outbreaks due to contamination with OPC-containing pesticides. [13]

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