Organic Phosphorous Compound and Carbamate Toxicity Follow-up

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

Further Outpatient Care

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  • Patients without any symptoms and with questionable or minimal exposure to OPCs or carbamates may be considered for discharge after 6-12 hours of observation.
  • Patients with residual neurologic symptoms should be given a follow-up appointment with a neurologist.
  • Follow-up with a psychiatrist should be arranged as indicated.
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Further Inpatient Care

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  • Most patients who require therapy for OPC poisoning warrant admission to the hospital for continued monitoring and treatment. Patients who require continuous monitoring or treatment should be admitted to the ICU.
  • Patients with clinically significant poisoning should be evaluated frequently to monitor their airway and respiratory secretions. In addition, frequent neurologic examination should be performed to evaluate for neuromuscular blockade.
  • Therapy is largely titrated to the physical findings. Atropinization is based on the drying of respiratory secretions, and oxime therapy is based on an improvement in neuromuscular signs.
  • A toxicologist may be of help in determining specific aging and reactivation times of the particular OPC or carbamate agent.
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Complications

Complications of OPC and carbamate poisoning include the following:

  • Intermediate syndrome
  • OPC-induced delayed neurotoxicity
  • Pancreatitis
  • Cardiac complications

Intermediate syndrome

Intermediate syndrome was first described in 1987 as a sudden respiratory paresis, with weakness in cranial nerves and proximal-limb and neck flexor muscles. [41] These clinical features appear 24-96 hours after exposure and are distinct from the previously described delayed neurotoxicity. Neck muscle weakness may be an early sign of intermediate syndrome. [42] Repetitive nerve stimulation studies may help in predicting which patients with intermediate syndrome are at risk for developing respiratory failure. [43]

Although intermediate syndrome is incompletely understood, more recent reports suggest that this is due to presynaptic and postsynaptic dysfunction of neuromuscular transmission and that it may result from insufficient oxime treatment. [44, 45]

Possible clinical indications of increased risk for intermediate syndrome are age ≥45 years and, on admission, an International Program on Chemical Safety Poison Severity Score (IPCS PSS) >2, and a Glasgow Coma Scale score of ≤10. [42]

OPC-induced delayed neurotoxicity

OPC-induced delayed neurotoxicity (OPCIDN) is a sensorimotor polyneuropathy that typically occurs 9-14 days after OP exposure. The patient initially presents with distal motor weakness and sensory paresthesias in the lower extremities, which may progress proximally and eventually affect the upper extremities. Most sources suggest that the mechanism involves inhibition of neuropathy target esterase (NTE), an enzyme that metabolizes esters in nerve cells. Some patients may recover over 12-15 months, but permanent losses, with spasticity and persistent upper motor neuron findings, have been reported. [14]

Pancreatitis

Pancreatitis has been reported as a rare complication. One case series reported that 12.76% of OP poisonings were associated with acute pancreatitis, although this has not been the experience in other series. [46, 47]

Cardiac complications

Cardiac arrhythmias have been associated with OPC poisoning. The most common ECG abnormality is QTc prolongation. [17] Cardiac complications may be due to direct cardiac toxicity. [48]

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Prognosis

In severe poisoning, death usually occurs within the first 24 hours if it is untreated. With nerve-agent poisoning, death may occur within minutes if untreated. Even with adequate respiratory support, intensive care, and specific treatment with atropine and oximes, the mortality rate is still high in severe poisonings. [49] A delay in treatment can also lead to late and permanent neurologic sequelae.

Most patients with minimal symptoms fully recover.

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Patient Education

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