Acute pesticide poisoning is an unusual and potentially fatal reason for visiting a family physician in the outpatient or emergency department setting. These episodes are likely to occur so infrequently that the physician must go through a steep learning curve with each encounter. However, a few items of history, knowledge of the small number of specific antidotes, and access to a limited number of resources (including the regional poison control center) will allow the physician to successfully initiate management for pesticide poisonings and most other poisons and to avoid mistakes from inexperience.
Poisoning events involving pesticides account for about 4 percent of all poisonings and result in approximately 15 deaths per year, or 0.02 percent of all pesticide poisoning events reported.
Recognition of Poisoning
Sometimes pesticide poisoning is obvious. The patient is brought in with a container of pesticide, the pesticide residue is still in the patient's mouth, and the patient has symptoms that are characteristic of the labeled pesticide. Often, this ideal scenario does not exist. The exposure may be uncertain, the pesticide found with the patient may or may not be the ingested poison, and the patient may exhibit no symptoms or symptoms uncharacteristic of the presumed exposure. Because one of the potential measures of toxicity of an exposure is its duration, time is of the essence.
Decontamination must be undertaken while questions about the specific exposure are answered and supportive or specific therapy is being initiated.
Respiratory and skin protection is required for health care workers involved with treating patients that have been poisoned. Latex gloves are inadequate for protection from many chemicals; only rubber gloves are appropriate for use in a poisoning situation. A full face mask with an organic vapor/high efficiency particulate air filter should be used until skin and gastrointestinal decontaminations are completed.
Skin decontamination is accomplished with a shower using soap, large amounts of water, and shampoo. Skin folds, areas underneath fingernails, ear canals, and other portions of the body that may trap chemicals should be inspected and cleaned carefully. Contact lenses should be removed, so the eyes can be inspected and irrigated thoroughly if exposure is suspected. Contaminated clothing should be removed, bagged, and laundered carefully. Leather items usually cannot be decontaminated and should be bagged and treated as hazardous waste.
Gastrointestinal decontamination may be accomplished in several ways, each having specific indications and contraindications. The American Academy of Clinical Toxicology (AACT) and the European Association of Poisons Centres and Clinical Toxicologists (EAPCCT) have recently produced a position statement1 on these therapies. A summary is included in the discussion of each potential therapy (Table 1). These therapies are also discussed in greater detail in the fifth edition of Recognition and Management of Pesticide Poisonings.2
|Consider if patient presents within 60 minutes of ingestion.|
|Insert orogastric tube.|
|Attempt aspiration first, followed by 100 to 200 mL normal saline, then aspiration.|
|Relatively contraindicated in hydrocarbon ingestion|
|Neurologically impaired: cuffed endotracheal tube prior to lavage|
|AATC/EAPCCT Position Statement: gastric lavage not routinely used in poisonings. It is indicated only When potentially life-threatening amount of poison is ingested and the procedure can be done within 60 minutes of ingestion.|
|Used only in combination with activated charcoal|
|Sorbitol (1 to 2 mL/kg or 70 percent solution in adults, 1.5 to 2.5 mL/kg of 35 percent solution in children)|
|Single dose only|
|Not recommended in poisonings that produce diarrhea (organophosphates, carbamates, heavy metals in particular) or those that produce ileus (paraquat and diquat)|
|AATC/EAPCCT Position Statement: Cathartic alone has no place in management of poisoned patient. No definite indications for use of cathartics and its routine use with activated charcoal is not endorsed. If it is used, it should be as a single dose. Numerous contraindications: absent bowel sounds, abdominal trauma or surgery, intestinal perforation or obstruction, volume depletion, hypotension, or ingestion of a corrosive substance.|
|Used in conjunction with a cathartic if patient presents within 60 minutes of ingestion. (Some authorities would use beyond 60 minutes if serious poisoning is suspected.)|
|Dose: Adults and children >12 years, 25 to 100 g in 300 to 800 mL water; children <12 years, 1 gm/kg in 300 mL water|
|Dose may be repeated in 2 to 4 hours if bowel sounds are present.|
|Antiemetic suppository for nausea|
|Administered by nasogastric tube if unable to tolerate or unable to swallow|
|Protect airway if hydrocarbon-containing pesticide or unknown pesticide contents.|
|AATC/EAPCCT Position Statement: Activated charcoal should not be used routinely in management of poisoned patients. Charcoal appears to be most effective within 60 minutes of ingestion and may be considered for use for this time period. There is insufficient evidence to support or deny its use beyond 60 minutes after ingestion.|
|Syrup of ipecac|
|No longer indicated for routine use|
|Dose: adults and children >12 years, 15 to 30 mL followed by 240 mL water; children <12 years, 15 mL preceded or followed by 120 to 240 mL water; infants six to 12 months of age, 5 to 10 mL preceded or followed by 120 to 240 mL water|
|Dose may be repeated in all age groups if emesis does not occur within 20 to 30 minutes.|
|Contraindicated in patients with diminished airway protective reflexes, ingestion of hydrocarbons with aspiration potential, ingestion of a corrosive substance, or ingestion of a substance for which advanced life support may be necessary within the next 60 minutes.|
|AATC/EAPCCT Position Statement: Ipecac syrup should not be administered routinely in poisoned patients. If it is used, it should be administered within 60 minutes of ingestion. Considered only in alert patients who have ingested a potentially serious toxin. Same contraindications as listed above.|
While skin and gastrointestinal decontamination are progressing, investigation into the background of the exposure should be ongoing. Family members, co-workers, and emergency response personnel should be interviewed to determine how the exposure occurred—inhalation, ingestion, skin contact, or combination (Is the environment safe now? Can others be protected from future exposure to poisoning risk?); if anyone else was exposed (Have all who were exposed been evaluated?); if there are other potential poisons involved (Are there symptoms that do not fit the presumed poison?); and if a specific antidote to the presumed poison exists (Has it been obtained and is it ready for administration?).
The label on the container of the pesticide involved is an invaluable resource for proper poisoning management. The Environmental Protection Agency requires a labeled statement of practical poisoning management and a telephone number for additional information. If the label is illegible or legible but more than a few years old, the regional poison control center should be able to provide up-to-date information on acute poisoning management.
With an unknown pesticide exposure, a land grant college Cooperative Extension Service agent who is familiar with local pesticide practices may be able to provide information about the most likely agrochemical in use in that area at a particular time of the year, on a particular crop, or in a specific environment.
The Extension Toxicology Network (EXTOX-NET) is available atwww.ace.orst.edu/info/extoxnet. The National Pesticide Information Center is available 9:30 a.m. to 7:30 p.m. EST at 800-858-7378 and atwww.npic.orst.edu/index.html/. The American Association of Poison Control Centers (AAPCC) has recently established a national poison control hotline number (800-222-1222) that connects callers to the nearest poison control center. The AAPCC Web address iswww.1-800-222-1222.info/poisonHelp.asp.
|Class||Mechanism of action/toxicity||Signs and symptoms||Treatment|
|Organophosphates ||Inhibit cholinesterase leading to excess acetylcholine||CNS—anxiety, seizures, Skeletal nerve-muscle junctions, autonomic ganglia—twitching, tachycardia, muscle weakness (nicotinic effects); peripheral cholinergic neuroeffector unctions— “all faucets on”— sweating, salivation, diarrhea, tearing (muscarinic effects); miosis (pinpoint pupils) most commonly, but 15 percent have mydriasis secondary to epinephrine release from adrenals due to nicotinic receptor stimulation.|
|Carbamates ||Reversible Cholinesterase Inhibition (carbamoyl-acetylcholinesterase [AChE] complex Dissociates much more easily and quickly than OP-AChE complex)||Cholinergic crisis with “all faucets on”; CNS depression with coma, seizures, hypotonicity in serious toxic exposures|
|Organochlorines ||Induction of hyperexcitable state in central and peripheral nervous system by disruption of normal flow of sodium and potassium across the axon membrane; may antagonize GABA-mediated inhibition in CNS||Seizures, headache, dizziness, nausea, vomiting, paresthesias, incoordination, tremor/twitching following topical treatment for lice/scabies or accidental or intentional ingestion of liquid pesticide|
|Pyrethrins are derived from chrysanthemums; pyrethroids are synthetic compounds with longer half-lives; both can produce toxic effects on the nervous system but are not well absorbed and are effectively and quickly detoxified by mammalian liver enzyme systems.||The most severe symptoms are seizures, though highly uncommon unless highly exposed (usually through ingestion of large quantities); tremor, incoordination, salivation, vomiting; topical exposure can produce short-term paresthesias, especially of the hands and face; a small portion of the population (1 to 3 percent) is allergic to pyrethrins/pyrethroids—resulting in symptoms ranging from nasal stuffiness to asthma.|
|Bacillus thuringiensis||Wide range of products derived from several varieties of this organism; highly limited effects on mammalian systems||Mild irritative pulmonary symptoms in some involved in manufacturing process, not in mixers or appliers; theoretical risk of respiratory infection in immunocompromised individuals; single corneal ulceration reported, successfully treated with standard antibiotics; mild gastroenteritis with heavy ingestion|
Diethyltoluamide—DEET (Muskol, Off!, Skeeter Beater, Skeeter Cheater, Skintastic for Kids, others)
|Mechanism of toxicity unknown||CNS depression followed by seizures; rare unless applied excessively under occlusion; mild skin irritating effects with repeated use; corneal and mucosal irritation; nausea and vomiting with ingestion and, rarely, hypotension, tachycardia with heavy dermal exposure|
Miscellaneous Solvents and Adjuvants
The liquid materials in which pesticides are dissolved and the solids on which they are adsorbed are chosen by the manufacturers to achieve ease in handling and application, and stability and maximal effectiveness of the active ingredient. The most commonly used solvents are petroleum distillates. Often, the odor that lingers after a pesticide application is that of the petroleum distillate rather than that of the active ingredient. Petroleum distillates may produce toxicities in themselves in large volume ingestions. Most adjuvants (emulsifiers, penetrants, and safeners) are potential skin and eye irritants of very low toxicity. Treatment of exposure is with decontamination by dilution with water.
With increasing use of integrated pest management and lower toxicity pesticides, acute pesticide poisoning will likely continue to be an infrequent reason for visiting a physician in the outpatient and emergency department settings. Because most of the commonly used pesticides have no specific antidote, decontamination of the skin, hair, eyes, and gastrointestinal tract is the primary mode of intervention. Recognition of the cholinergic syndrome associated with organophosphate and carbamate exposure allows for specific treatment of this increasingly rare event. Some members of other pesticide classes also have specific antidotes, making identification of the chemical necessary for optimal therapy. This emphasizes the need for teamwork with the patient, family, employer/supervisor, or Cooperative Extension Service agent.
Accidental pesticide exposures invite consideration of educational interventions to prevent recurrences, whether they be on an individual, family, community, or industry-wide scale. Because up to one half of pesticide poisonings are intentional in some age groups, particularly teenagers, the family physician must use the event as a trigger for screening for depression or other psychiatric illnesses.