Case Study, First Patient

Disorientation, Ataxia, and Abdominal Symptoms in Visitors to a Municipal Airport

A 67-year-old man is brought to the Emergency Department (ED) of a small community hospital where you are the family physician on call. The patient is experiencing ataxia, dizziness, and vomiting. He is hyperventilating. On physical examination, the patient appears well nourished, but agitated and disoriented. There is no odor of ethanol on his breath.

Vital Signs

The patient's vital signs are

• blood pressure (BP): 120/80 mm Hg
• temperature: 98.5° F
• pulse: 80 beats/minute
• respirations: 40 breaths/minute

Neurologic examination is otherwise normal with no crucial findings. There is no nystagmus. Abdominal and cardiorespiratory examinations are also normal.

Additional Information

The patient's friend brought him to the ED. The friend said the patient complained of dizziness and had begun to vomit late last night. This morning the patient was hyperventilating and continued to vomit. Both men are retired pilots who teach at the local airport's ground school. Because two other people had collapsed at the airport that morning and were taken by ambulance to another hospital, the friend wonders if the food at the airport cafeteria is responsible. Both he and the patient had hot dogs and coleslaw, but the friend states that he feels fine.

Results of Lab Tests

• blood ethanol and drug screen are negative
• arterial blood gases (ABG) results: pH 7.10; PaCO₂=20 mm Hg; PaO₂ =95 mm Hg; and Bicarbonate, =8 mEq/L
• sodium: 145 mmol/L (normal 135-145 mmol/L (Jacobs DS 1996))
• potassium: 3.8 mmol/L (normal 3.1-5.3 mmol/L)
• chloride: 105 mEq/L ( normal 98-109 mEq/L)
• BUN: 20 mg/dL (normal 8-18 mg/dL)
• creatinine: 1.0 mg/dl (normal 0.6-1.2 mg/dL)
• glucose: 80 mg/dl ( normal 65-110 mg/dL)
• calculated anion gap: 32 (normal 12 to 16)

Normal values may vary from lab to lab and depend upon the elevation above sea level.

Case Study, Second Patient

Less than 30 minutes later, a 4-year-old boy is brought to the ED. On examination you find a sleepy but arousable child. There is no evidence of trauma or focal neurologic signs. Abdominal and cardiorespiratory examinations are normal.

Vital Signs

The patient's vital signs are

• BP, 94/76 mm Hg
• rectal temperature: 98.5° F
• respirations: 12 breaths/minute
• pulse: 78 beats/minute

Additional Information

The parents tell you they were attending a local fliers' club luncheon at the airport. When they found the child staggering and incoherent, they rushed him to the ED. On the way, he vomited in the car.

Results of Lab Tests

You order the same laboratory tests for the child that you ordered for the 67-year-old patient. The tests reveal that the child is

• hypoglycemic
• has slight acidosis
• an anion gap of 13

Additional Information

You contact the local health department. You are told they are investigating the earlier incidents at the airport. They suspect the airport's water supply is contaminated, but they have not identified the contaminant.

Initial Check Questions

1. What would you include in the list of problems for each patient? What is the differential diagnosis for an anion gap metabolic acidosis?

2. What additional tests, if any, will you order for these patients?

3. How will you initially treat these patients?

4. What questions would health department investigators ask airport visitors and employees to establish the exposure source?

5. The health department identifies the water contaminant as ethylene glycol. When construction crews at the airport were repairing the water supply system, they inadvertently connected the water from the heating system to the drinking water system. The concentration of ethylene glycol measured at the cafeteria's water source was 9% (90,000 ppm). The US Environmental Protection Agency (EPA) has an ethylene glycol drinking water quality guideline of 7 ppm (FSTRAC 1990). The lethal dose of 95% ethylene glycol is about 100 ml for an adult or 1.4 ml/kg.

   Who in the case study may be at risk of adverse health effects?

   Explain.

6. A week after the water contamination incident, a patient comes to your office. He de-ices airplanes at the airport and was drenched with de-icing fluid in a major spill yesterday. He knows that de-icing agents contain large amounts of ethylene glycol. He immediately showered and changed clothes after the incident, but he is worried about possible adverse health effects; for example, he wonders if cancer could develop. What will you tell him?

7. A pregnant worker at the airport consults you because she drank tea brewed with the contaminated water. Although she consumed only a small amount of tea and had no ill effects, she is worried that her fetus will be adversely affected. How will you counsel her?

8. It was later determined that during dinner at the cafeteria, the 67-year-old man had consumed several cups of coffee, while his friend, who did not become ill, drank only soda from a can. The serum ethylene glycol level for the 67-year-old patient is 55 mg/dl; the anion gap is 35. How will you treat the 67-year-old patient?

9. The child's ethanol level is 85 mg/dl. You repeat the ethanol test, and again the result is high. The parents are incredulous but admit that the child was not supervised closely during the luncheon, where wine and cocktails were served. Potential ethylene glycol exposure sources for the child could not be identified. How will you treat the child?

Initial Check Answers

1. The man's medical problems include
   • ataxia
   • vomiting
   • agitation
   • disorientation
   • hyperventilation
   • elevated anion-gap metabolic acidosis

   The child's medical problems include

   • somnolence
   • ataxia
   • mental status changes
   • vomiting
   • hypoglycemia
   • low body temperature
   • slight anion-gap metabolic acidosis

   (Common toxic agents associated with an elevated anion gap are shown in Table 2.)

2. Additional testing of these patients should include:
   • urinalysis
   • complete blood count
   • serum osmolality measured by the freezing-point–depression technique
   • ethylene glycol and methanol levels,
   • ammonia, acetaminophen, and aspirin levels, and
   • liver function tests.

   More information for this answer can be found in the section “What laboratory tests can help in evaluating patients exposed to ethylene glycol?”

3. Several hours have passed since the ingestion, and emesis or gastric lavage will be of little value. Activated charcoal is likely to be ineffective unless there is a question of a possible overdose. It is important to act promptly to correct the metabolic acidosis and to prevent further conversion of the remaining ethylene glycol into its toxic metabolites. The acidosis can be corrected with sodium bicarbonate therapy. Intravenous administration of ethanol or fomepizole (as described in the Treatment and Management section) will inhibit further metabolism of ethylene glycol. At serum ethylene glycol levels of 50 mg/dl or greater, hemodialysis should be started to remove ethylene glycol and its metabolites from the blood. Pyroxidine and thiamine may also be administered.

   The child may be intoxicated with only ethanol or with ethanol and ethylene glycol. If intoxication is due to ethanol alone, carefully monitor blood glucose and ethanol levels until the intoxication resolves. However, you must consider that ethylene glycol poisoning may be a complication. Because ethanol competitively inhibits ethylene glycol metabolism, you may choose to let the ethanol level decrease naturally to 70 mg/dl, then administer ethanol intravenously to maintain that level. If laboratory results indicate that ingestion of ethylene glycol occurred, immediately transfer the child to a pediatric unit to undergo hemodialysis.

   More information for this answer can be found in the section “How should patients exposed to ethylene glycol be treated?”

4. The most common sources of epidemic poisonings include contaminated food, beverages, and water supplies. The investigators would ask about types of food and drink available at the airport. They would take a detailed history of food and beverage intake from the patients and all others at the airport. They would attempt to find a common factor that would include those who were ill and exclude those who did not become ill. By gathering such data from a large number of people and statistically analyzing the data, the exposure source can usually be identified or possibilities restricted.

   More information for this answer can be found in the section “Where is ethylene glycol found?”

5. The lethal dose of antifreeze (95% ethylene glycol) is about 100 ml or 1.4 ml/kg, although there is wide variation among reported cases. A cup (240 ml) of the contaminated water would contain about 22 ml of ethylene glycol. This dose could cause significant toxicity. Even mild symptoms of ethylene glycol poisoning would be a concern for air traffic controllers and other airport personnel responsible for judgments affecting many lives. All employees and visitors who consumed beverages or food that was prepared using water at the airport should be examined.

   More information for this answer can be found in the section “How are people exposed to ethylene glycol?”

6. Absorption of ethylene glycol is minimal through intact skin and is not likely to lead to toxic effects. Because the patient showered and changed clothes immediately, it is unlikely that he will experience toxic effects from the spill. In the case of chronic exposure during the de-icing process, few particles from a spraying device are likely to be respirable, so inhalation of ethylene glycol would be minimal. Contact during the de-icing process would not contribute substantially to toxicity, especially if protective clothing and respiratory protection were used. There is no evidence that ethylene glycol causes cancer in humans.

   More information for this answer can be found in the section “What are the physiologic effects of ethylene glycol?”

7. You can inform the patient that studies in experimental animals indicate that ethylene glycol at the high, prolonged levels can cause developmental effects although no studies in humans specifically assess the effects of ethylene glycol on fetal development.

   More information for this answer can be found in the section “What are the physiologic effects of ethylene glycol?”

8. Several hours have passed since the ingestion, and emesis or gastric lavage will be of little value. Activated charcoal is likely to be ineffective. However, it is important to act promptly to correct the metabolic acidosis and to prevent further conversion of the remaining ethylene glycol into its toxic metabolites. The acidosis can be corrected with sodium bicarbonate therapy. Intravenous administration of ethanol or fomepizole (as described in the Treatment and Management section) will inhibit further metabolism of ethylene glycol. At serum ethylene glycol levels of 50 mg/dl or greater, hemodialysis may be instituted to remove ethylene glycol and its metabolites from the blood. Pyroxidine and thiamine may also be administered. Recent studies show that even when ethylene glycol levels exceed 50 mg/dL, hemodialysis can be avoided and patients can be treated solely with fomepizole. However if the level exceeds 50 mg/dL and is accompanied by renal failure and severe metabolic acidosis, then hemodialysis is indicated. The bottom line is that levels of ethylene glycol per se should not determine the indication for dialysis, but should be considered along with the clinical presentation.

   More information for this answer can be found in the section “How should patients exposed to ethylene glycol be treated?”

9. The child could be intoxicated with ethanol alone or with ethanol and ethylene glycol. If intoxication is due only to ethanol, carefully monitor blood glucose and ethanol until the intoxication resolves. However, you must consider that ethylene glycol poisoning may be a complication. Because ethanol competitively inhibits ethylene glycol metabolism, you may choose to let the ethanol level decrease naturally to 70 mg/dl, then administer ethanol intravenously to maintain that level. If laboratory results indicate that ingestion of ethylene glycol occurred, immediately transfer the child to a pediatric unit to undergo hemodialysis.

   More information for this answer can be found in the section “How should patients exposed to ethylene glycol be treated?”