Case Study 9

History

A 2 year-old (12 kg) girl was brought to the hospital by ambulance after having a witnessed seizure at home. The child was healthy, born at term, and without any significant past medical history. Although her family had recently immigrated to the United States, she was followed in a primary care clinic and was fully vaccinated. She had one screening test for lead, which was “normal.” Her mother relates that their house had problems with roaches, mice, and rats and she thinks her husband applied a chemical to deal with the problem.

About 20 minutes before the girl became ill, her mother saw the child pick up something from the corner of the room and immediately thereafter removed some material that looked like food from the child’s mouth. She subsequently lost consciousness and began to shake. The mother called 9-1-1 and when EMS arrived the child was intermittently seizing. Lorazepam (1 mg IM) was administered and EMS gave the child supplemental oxygen for transport. The paramedics reported that the child stopped seizing during transport but started again upon arrival to the emergency department.

On arrival, the child was seizing with the following vital signs: blood pressure, 90/40 mm Hg; pulse, 160 beats/min, respiratory rate, 36 breaths/min; temperature, 100°F (37.7°C); oxygen saturation, 100% on a 100% nonrebreather mask. There were no signs of trauma. The skin was moist, pupils were 4 to 5 mm and fixed, the chest was clear, heart sounds were regular, and her abdomen was soft. Neurologic examination revealed ­repetitive symmetrical movements of the limbs, slight eye deviation to the left, and a lack of responsiveness to stimulation.

Another 1 mg dose of lorazepam was given IM, while an IV was being inserted. A rapid bedside glucose was 160 mg/dL, and blood samples were obtained for complete blood count, electrolytes, liver function tests, and creatine phosphokinase. The child continued to seize and a 2 mg IV dose of lorazepam was administered that terminated the seizure. Repeat vital signs were notable for a pulse of 165 beats/min and a rectal temperature of 100.6^o F (38.1^o C). Blood cultures were sent and the child was given an empiric dose of ceftriaxone. An ECG was obtained and showed sinus tachycardia with normal axis and intervals.

In addition to infectious, structural, and traumatic causes for repeated seizures, the history is suggestive of pesticide poisoning. Pesticides are defined by the US Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) as “any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest, and any substance or mixture of substances intended for use as a plant regulator, defoliant, or desiccant.” Since 1947, the production, use, and distribution of pesticides in the United States have been regulated under FIFRA and its subsequent amendments in 1972, 1975, and 1978. In 1970, the US Environmental Protection Agency (EPA) was given the authority to administer and enforce FIFRA regulations. Under FIFRA, all pesticides and their manufacturers must be registered with the EPA, and the pesticide must be classified for either general use or restricted use by licensed or certified applicators. Additionally, according to FIFRA, rodenticides are classified by their toxicities and must be labelled by signal words as designated in Table CS9–1. The WHO applies a similar classification scheme for all pesticides based on either oral or dermal LD₅₀ as shown in Table 113–1.

Unfortunately, as is so commonly the case, not only was the mother unaware of the name or type of pesticide used, but also both the original container and label were missing. Furthermore, there was a possibility that the product used was brought from the parent’s home country and was either illegal or unlicensed in the United States. As a result, clinicians are often forced to provide empirical treatment based largely on clinical diagnosis. An understanding of the likely possibilities improves both diagnostic utility and treatment decisions.

A review of Table CS9–2, and chapters throughout this text, especially those that immediately follow this case will help identify those pesticides when ingested that are most likely to result in seizures or status epilepticus. The possible xenobiotics include organic phosphorous compounds and carbamates, organic chlorines, monofluoroacetate and fluoroacetamide, strychnine, thallium, zinc and aluminum phosphide, and tetramine. The absence of associated clinical manifestations helps eliminate some of the choices: organic phosphorous compounds and carbamates (eg, salivation, lacrimation, urination, defecation, bradycardia, bronchorrhea, miosis), thallium (the onset was rapid and there was an absence of painful peripheral neuropathy), strychnine (not true seizures, consciousness should be preserved until hyperthermia, hypoxia, or hypercarbia becomes severe), and aluminum phosphide (absence of vomiting with characteristic odor of rotten fish). Although routine laboratory testing has little utility here, the absence of a profound metabolic acidosis might suggest that monofluoroacetate and fluoroacetamide are not responsible for this clinical presentation. Certain dangerous rodenticides imported for illicit use include tetramine (status epilepticus) and aldicarb (a carbamate found in tres pasitos). Unfortunately, since there are no rapidly available tests to help establish this diagnosis, treatment will have to be based entirely on the clinical assessment.

Shortly after the third dose of lorazepam the child began to seize again and endotracheal intubation was performed. ­Following intubation the child was placed on a continuous infusion of propofol. A nasogastric tube was inserted and 10 g of activated charcoal were instilled into the stomach. The child was transferred to the PICU and attached to a video EEG monitor where intermittent seizure activity was noted over the next 12 to 16 hours. A CT scan of the head was normal and a lumbar puncture was performed to exclude meningitis. The following day the father brought in the original package and the product was identified as tetramine.

Over the subsequent 24 hours the propofol infusion was titrated to a lower dose and then discontinued. The child was able to be extubated and appeared clinically normal. Since the package was brought from their home country and not imported, authorities were not notified. The parents were educated about safe use of pesticides and a social worker was able to help coordinate legal exterminating efforts by the landlord.

Authors from previous editions, including Neal E. Flomenbaum, Mary Ann Howland, Richard Weisman, Rebecca Tominack, and Susan Pond, contributed to the development of Tables CS9–1 and CS9–2 as well as the discussion of FIFRA.