The poisoned patient

Today we discussed an approach to the poisoned patient. Some points:

Detective work is often required in these situations, and history from witnesses / bystanders / family members / paramedics, etc. often provides a key clue

Always ask about

1) Details of what was found near the patient and events (including number of pills left in bottles- gives the "worst case scenario" in terms of amount of a substance taken)

2) Timing of ingestion

3) History of what medications the patient was taking, including possibly from pharmacy directly
4) Medications/substances the patient would have had access to (including family members' medications)

5) History of previous intoxications, psychiatric history

In many cases, collateral history is not possible, and even the most thorough searching does not reveal the substance taken. In these cases, the physical exam often reveals a "toxidrome" that can point to the substance and guide therapy.

Toxidromes (and some mnemonics)

Sympathomimetic
febrile, flushed, tachycardic, hypertensive (more than anticholinergic), mydriasis, diaphoretic (distinction from above)
Examples: cocaine, amphetamines, pseudoephedrine
Treatment: Benzodiazepines, supportive

Narcotic
dec. LOC, hypotension, dec. respiratory rate, miosis. Response to naloxone
Examples: Morphine, other opiates
Treatment: Naloxone

Anticholinergic
hot as a hare, dry as a bone, red as a beet, mad as a hatter, blind as a bat febrile, flushed, tachy, mydriasis, dry mucosa, decreased bowel sounds, urinary retention, hallucinations Examples: Benadryl (or other antihistamines), Gravol, tricyclic antidepressants, antiparkinsonians
Treatment: Acetylcholinesterase inhibitor (e.g. physostigmine)

Cholinergic:
"SLUDGE and the killer B's": salivation, lacrimation, urination, diaphoresis, gi (diarrhea), emesis. Killers: bradycardia, bronchorrhea
Examples: Organophosphate insecticides, donepezil, rivastigmine, galantamine
Treatment: Atropine

Sedative / hypnotic:
dec. LOC, dec. respiratory rate, slurred speech, ataxia, nystagmus
No response to naloxone
Examples: Phenobarbital, alcohols, benzodiazepines
Treament: No specific antidote for phenobarbital; flumazenil for benzo; EtOH or fomepizole for MeOH

Managing the poisoned patient:

1) ABC- may need definitive airway management, supportive care

2) Try to identify agent or toxidrome as above
Always remember co-ingestions! Ways to identify these are by the anion gap, osmolal gap, ECG (looking for signs of cardiac toxicity), and serum + urine toxicology screens

3) Administer "universal antidotes" where appropriate- oxygen, glucose, naloxone, thiamine

4) Think about preventing absorption
Activated charcoal or whole bowel irrigation
Charcoal: If less than 4h from ingestion (preferably less than 2h). Want 10:1 ratio of charcoal to substance. Not for caustics, metals (Li, Fe), hydrocarbons. Repeated charcoal with drugs with enterohepatic circulation- theophylline, phenytoin, carbamazepine
Whole bowel irrigation: Enteral PEG-LYTE administration until rectal effluent is clear. It is effective with drug packets, extended release preparations, substances not well adsorbed by activated charcoal. Dose 2L per hour PO or NG until clear.

5) Think about a specific antidote if one exists

6) Think about enhancing elimination
(e.g. by dialysis or alkalinization of urine)

7) Always call poison control!

Dialyzable drugs:
Salicylates, alcohols, Li, phenobarb, valproate, theophylline, carbamazepine

Links:

Click here for a NEJM clinical case outlining approach to the poisoned patient

Click here for a review of a new potential antidote to lipophilic drug intoxicatios, a lipid emulsion- "Intralipid"