Toxic Ingestions and Overdoses
5
Toxidromes
Sympathomimetic anticholinergic cholinergic opioid sedative
1-2 hrs
Charcoal Window
Activated charcoal effective window
4 hrs
APAP Level
Check acetaminophen at 4 hours post-ingestion
Toxidrome Pattern Recognition
the presentation tells you the poison classTachycardia, hypertension, dilated pupils, hyperthermia, agitation
Tachycardia, dry flushed skin, dilated pupils, urinary retention, hyperthermia
SLUDGEM (salivation, lacrimation, urination, defecation, GI distress, emesis, miosis)
Pinpoint pupils, respiratory depression, altered consciousness, bradycardia
CNS depression, respiratory depression, hypotension, normal pupils
Critical Antidotes
Flumazenil is contraindicated in chronic benzo use and mixed overdoses with TCAs. Always assess for chronic benzodiazepine use and coingestants before considering reversal.
Key Values to Memorize
APAP level at 4 hours
NAC within 8 hrs ideal
Charcoal within 1-2 hrs
QRS >100ms in TCA = bicarb
Naloxone onset 1-2 min IV
Rumack-Matthew nomogram
toxicology questions reward pattern recognition
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Practice CCRN QuestionsExam Traps
Flumazenil can cause seizures in chronic benzodiazepine users
Flumazenil reverses benzodiazepine effects by competitive antagonism at the GABA receptor. In a patient with chronic benzodiazepine use or dependence, abrupt reversal can precipitate life-threatening seizures. It is also contraindicated in mixed overdoses involving tricyclic antidepressants because it removes the seizure-protective effects of benzodiazepines.
TCA overdose gets sodium bicarbonate, not antiarrhythmics
Tricyclic antidepressant toxicity causes sodium channel blockade leading to QRS widening, hypotension, and seizures. The treatment is sodium bicarbonate, which overcomes the sodium channel blockade and alkalinizes the serum. Standard antiarrhythmic drugs can worsen the conduction abnormality.
Acetaminophen toxicity has NO early symptoms
In the first 24 hours after an acetaminophen overdose, the patient may feel perfectly fine or have only mild nausea. Liver damage is occurring silently. By the time symptoms appear (RUQ pain, jaundice, coagulopathy at 48-72 hours), the damage may be irreversible. That is why the 4-hour level and the Rumack-Matthew nomogram guide treatment.
The Rumack-Matthew nomogram guides NAC treatment decisions
Plot the serum acetaminophen level against time since ingestion on the nomogram. If the level falls above the treatment line, start N-acetylcysteine (NAC). NAC is most effective within 8 hours of ingestion but can still benefit patients up to 24-72 hours after ingestion.
Flumazenil Warning
Chronic benzo user + flumazenil = seizures. Mixed OD with TCAs + flumazenil = seizures. When in doubt, do NOT give flumazenil.
Antidote Quick Reference
Opioid = naloxone. APAP = NAC. TCA = bicarb. Organophosphate = atropine + pralidoxime. Digoxin = digoxin Fab.
A toxidrome is a pattern of signs and symptoms that points to a specific class of poison. It is like a crime scene where the clues tell you what weapon was used even if no one saw the crime. Dilated pupils + tachycardia + hyperthermia = sympathomimetic. Pinpoint pupils + bradycardia + respiratory depression = opioid.
Each toxidrome has a specific antidote that directly counteracts the poison. Naloxone blocks opioid receptors. NAC replenishes glutathione to protect the liver from acetaminophen metabolites. Atropine blocks the excess acetylcholine in organophosphate poisoning.
Acetaminophen is the most dangerous because it hides. The patient feels fine for the first 24 hours while the liver is being destroyed. By the time they look sick, it may be too late. That is why the 4-hour level and the nomogram exist. Check it. Do not wait for symptoms.
Flumazenil seems logical for benzodiazepine overdose. But in chronic users, it rips away the drug the brain has adapted to, triggering withdrawal seizures. And in mixed overdoses, the benzodiazepine may be the only thing preventing TCA-induced seizures. Sometimes the "antidote" is more dangerous than the overdose.
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