Setting: ED
CC: Vomiting
VS: BP: 110/70 mm Hg; P: 108 beats/minute T: 98°F; R: 12 breaths/minute
HPI: A 46-year-old man comes to the ED after intentionally trying to end his life by taking a bottle of acetaminophen pills within the last hour. He took 30 extra-strength 500-mg pills. He is extremely nauseated. He has not vomited yet.
What is the single most important thing to do first?
a. Test acetaminophen level now.
b. Test acetaminophen level in 4 hours.
c. Give N-acetylcysteine (NAC) and charcoal.
d. Give N-acetylcysteine (NAC) alone.
e. Order a psychiatry consultation.
f. Do gastric lavage.
Answer c. Give N-acetylcysteine (NAC) and charcoal.
NAC is a specific antidote for acetaminophen. Charcoal blocks absorption, but does not interfere with NAC. A level of the drug is important, but not as important as preventing toxicity of the drug. Gastric lavage has no utility in acetaminophen overdose ever. Charcoal and NAC are superior to any attempt at gastric emptying. Acetaminophen level reaches its peak in 4 hours after ingestion, but is still not as important as preventing toxicity. On CCS, do not expect a consultant to do anything for you.
Knowing the amount of acetaminophen ingested is more than enough reason to give NAC and charcoal. You do not have to wait for the blood level of acetaminophen.
• Do not wait for blood level.
• Give the NAC and charcoal.
PMHX:
Alcoholism
Medications: none
Acetaminophen overdose: Quick administration of NAC and charcoal is essential to protect the liver. Do not wait for time it takes to do the physical examination.
Orders:
NAC IV or oral depending on the presence of vomiting
Charcoal
CHEM-20
Make sure you get baseline liver function tests (LFTs)!
PE:
General: nauseated, no abnormalities seen
Chest, Heart, Abdomen: normal
Neurological: no focal deficits; normal mental status
Lavage removes:
• Fifty percent at 1 hour
• Fifteen percent at 2 hours
• Less than NAC and charcoal
Giving ipecac on an empty stomach is always wrong.
When is gastric emptying the right answer?
a. Never
b. For caustic ingestions (e.g., lye, drain cleaner)
c. For pills with no antidote within the hour of ingestion
d. For more than 2 hours after ingestion
Answer c. For pills with no antidote within the hour of ingestion
Gastric emptying is almost never the correct thing to do. It is rarely done. Gastric emptying with an Ewald gastric tube is done only within 1 to 2 hours of ingestion of a pill that has no other antidote. Lavage is absolutely contraindicated with the ingestion of caustics. When you lavage out caustics, all you do is increase the chance of burning the mouth and upper gastrointestinal (GI) tract on its way out of the stomach. Emptying is absolutely useless when more than 2 hours have passed since the ingestion.
Normal gastric emptying time:
• For pills without food, 30 to 60 minutes
• With most foods, 2 hours
Initial Orders:
NAC
Charcoal
Repeat CHEM-20 and LFTs
Repeat acetaminophen level
Once you administer NAC and charcoal, there is nothing more that can be actively done to reverse or prevent hepatic toxicity from acetaminophen. Acetaminophen is metabolized into an end product that is a profound oxidant stress to the liver. Acetaminophen metabolites deplete the body of glutathione reductase.
• NAC restores glutathione reductase.
• Charcoal, microscopically, has an enormous surface area to bind drugs.
Reports:
CHEM-20 and LFTs: normal
Acetaminophen level: elevated
Drug Toxicity = Aspartate Aminotransferase (AST)
What in this patient’s history makes it more likely for him to have liver damage or toxicity?
a. Time from ingestion to arrival
b. Use of NAC at same time as charcoal
c. History of alcoholism
d. Not doing gastric emptying
e. Age >30 years
f. Gender
Answer c. History of alcoholism
Alcoholics need less acetaminophen to result in toxicity. The liver is already partially damaged in alcoholics. Alcoholics have already undergone a significant degree of oxidant stress to the liver. In an average-sized person, toxicity begins above 10 g of acetaminophen. Fatality from the depletion of glutathione reductase begins around 15 g of ingestion. In an alcoholic, toxicity may occur from 6 to 8 g of ingestion and fatality at 10 to 12 g of ingestion.
Alcoholism decreases the toxic dose needed to hurt the liver.
As you move the clock forward, remember to give repeated doses of oral charcoal and NAC. Repeat the chemistry level every day to be sure there is no liver toxicity. There is nothing more you can do in therapy besides NAC and charcoal, but it will be expected on CCS that you should know that you need to check LFTs and prothrombin time (PT). If toxicity does occur and it is severe, all you can do is try to get a liver transplantation.
Orders:
LFTs
PT
NAC is only effective if used within 24 hours after the ingestion.
NAC is given for 1 to 2 days. Charcoal is given for the first 24 hours. Charcoal will not only block the absorption of acetaminophen, it will remove it from the bloodstream after it has been well absorbed through the small bowel. You need 2 to 3 days to be sure there is no liver toxicity.