Pediatric Organophosphates Toxicity 

  • Author: William Freudenthal, MD; Chief Editor: Timothy E Corden, MD   more...
 
Updated: Nov 15, 2011
 

Background

Organophosphates and carbamates are the most frequently used insecticides worldwide. These compounds cause 80% of the reported toxic exposures to insecticides. Organophosphates produce a clinical syndrome that can be effectively treated if recognized early. The typically described clinical syndrome in adults often does not occur in young children.[1, 2, 3, 4]

Organophosphates were first discovered more than 150 years ago; however, their widespread use began in Germany in the 1920s, when these compounds were first synthesized as insecticides and chemical warfare agents. Interest in the effects of these compounds on humans has increased in recent years due to their potential use as weapons of mass destruction.[5]

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Pathophysiology

Organophosphates form an initially reversible bond with the enzyme cholinesterase. The organophosphate-cholinesterase bond can spontaneously degrade, reactivating the enzyme, or can undergo a process called aging. The process of aging results in irreversible enzyme inactivation.

Cholinesterase is found in 2 forms: an RBC form, which is known as true cholinesterase, and a plasma form, which is known as pseudocholinesterase. Cholinesterases rapidly hydrolyze the neurotransmitter acetylcholine into inactive fragments. Acetylcholine is found in sympathetic and parasympathetic ganglia and in the terminal nerve endings of postganglionic parasympathetic nerves at the motor endplates of nerves in the skeletal muscle. Inactivation of the enzyme allows acetylcholine to accumulate at the synapse, leading to overstimulation and disruption of nerve impulses. Skeletal-muscle depolarization and fasciculations occur secondary to nicotinic stimulation at the motor endplate.

Muscarinic effects occur at the postganglionic parasympathetic synapses, causing smooth-muscle contractions in various organs including the GI tract, bladder, and secretory glands. Conduction can be delayed in the sinus and atrioventricular (AV) nodes. Dysrhythmias are frequently reported; these typically include bradycardia, though tachycardia can also occur.

Acetylcholine receptors are widely dispersed throughout the CNS. The activation of these receptors causes a wide range of effects, including CNS stimulation, seizures, confusion, ataxia, coma, and respiratory or cardiovascular depression.

Organophosphates are generally highly lipid soluble and are well absorbed from the skin, mucous membranes, conjunctiva, GI system, and respiratory system.

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Epidemiology

Frequency

United States

In 2004, 102,754 exposures were reported. In children younger than 6 years, 52,174 exposures were reported; however, no deaths were reported in this age group. Many more exposures probably occur, but patients with minor symptoms often do not seek medical care.

International

Worldwide, pesticide poisonings cause an estimated 20,000 deaths and cause more than one million serious poisonings annually.

Mortality/Morbidity

  • Most morbidity and mortality results from anoxic injury due to respiratory failure. Clinical effects range from mild flulike symptoms with low-level exposures to life-threatening respiratory failure with larger exposures.
  • Childhood deaths and reported poisonings in the United States have declined over the last few decades, partly because of educational efforts and improved regulation and packaging.

Race

No known racial differences in mortality or morbidity are reported.

Sex

No differences in clinical effects between the sexes are known.

Age

  • In 2004, more than 50% of the insecticide exposures in the United States occurred in children younger than 6 years.
  • Children are at a significantly increased risk worldwide, particularly in Africa and other developing regions, where the widespread availability and use of organophosphates and the lack of regulation and safety packaging are high risk factors for exposure.
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Contributor Information and Disclosures
Author

William Freudenthal, MD  Staff Physician, Department of Emergency Medicine, St. Vincent Hospital Indianapolis, IN

William Freudenthal, MD is a member of the following medical societies: American College of Emergency Physicians and Association of Military Surgeons of the US

Disclosure: Nothing to disclose.

Coauthor(s)

Mark E Ralston, MD, MPH  Staff Pediatrician, Naval Hospital Oak Harbor; Assistant Professor of Pediatrics, F Edward Hebert School of Medicine, Uniformed Services University of the Health Sciences

Mark E Ralston, MD, MPH is a member of the following medical societies: American Academy of Pediatrics

Disclosure: Nothing to disclose.

Specialty Editor Board

Michael E Mullins, MD  Assistant Professor, Division of Emergency Medicine, Washington University in St Louis School of Medicine; Attending Physician, Emergency Department, Barnes-Jewish Hospital

Michael E Mullins, MD is a member of the following medical societies: American Academy of Clinical Toxicology and American College of Emergency Physicians

Disclosure: Johnson & Johnson stock ownership None; Savient Pharmaceuticals stock ownership None

Mary L Windle, PharmD  Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

Jeffrey R Tucker, MD  Assistant Professor, Department of Pediatrics, Division of Emergency Medicine, University of Connecticut School of Medicine, Connecticut Children's Medical Center

Disclosure: Merck Salary Employment

Daniel Rauch, MD, FAAP  Director, Pediatric Hospitalist Program, Associate Professor, Department of Pediatrics, New York University School of Medicine

Daniel Rauch, MD, FAAP is a member of the following medical societies: Ambulatory Pediatric Association, American Academy of Pediatrics, and Society of Hospital Medicine

Disclosure: Baxter Honoraria Consulting

Chief Editor

Timothy E Corden, MD  Associate Professor of Pediatrics, Co-Director, Policy Core, Injury Research Center, Medical College of Wisconsin; Associate Director, PICU, Children's Hospital of Wisconsin

Timothy E Corden, MD is a member of the following medical societies: American Academy of Pediatrics, Phi Beta Kappa, Society of Critical Care Medicine, and Wisconsin Medical Society

Disclosure: Nothing to disclose.

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