approach to the poisoned patient

1. history & physical

history

The Ingestion: What? When? How much? Route?
Co-ingestions: Ethanol, ASA, Acetaminophen (the “silent killers”).
Context: Intentional (suicide note?) vs. Accidental. Environmental (CO risk?).
PMHx: Medications (access to home meds), Allergies, Substance use.

physical

Vitals: Temp (Hyperthermia is critical), HR, BP, RR, Saturation.
Neurologic: GCS, Pupil size/reactivity, Clonus/Rigidity/Reflexes (Serotonin vs NMS).
Skin: Dry vs. Diaphoretic (Anticholinergic vs Sympathomimetic), tracks, burns.

stat investigations

Labs: CBC, Lytes, BUN/Cr, Ca/Mg/PO4, LFTs, CK, Troponin, Glucose.
Gases: ABG/VBG + Lactate.
Toxicology: Acetaminophen & Salicylate levels (ALWAYS), Ethanol, Urine Drug Screen (low yield but often ordered).
Other: $β$ -HCG (females), 12-Lead ECG (intervals), Urinalysis (crystals).

quick calculations

Anion Gap: $N a - (Cl + H C O_{3})$ . Normal $< 12$ .

Calculated Osmolality: $2 [N a] + Gl u cose + U re a$ .

Osmolar Gap: $M e a s u re d O s m - C a l c u l a t e d O s m$ . Normal $< 10$ .

High Gap? Think Toxic Alcohols (Methanol/Ethylene Glycol).

2. resuscitation (abcde)

Priority is always stabilisation before decontamination.

Airway: Early intubation for GCS < 8 or predicted decline (e.g., TCA, Salicylate fatigue).
Breathing: Oxygen, ventilation.
Circulation:
- Hypotension: IV Fluids $\to$ Vasopressors (Norepinephrine).
- Specific: Calcium (CCB/Beta-blocker), Glucagon (Beta-blocker), High-dose Insulin (CCB/BB), Intralipid (Local anaesthetics/Lipophilic drugs).
Disability:
- Coma Cocktail (Diagnostic/Therapeutic):
  - Dextrose: If hypoglycaemic.
  - Thiamine: 100mg IV (Alcoholics - see Alcohol Withdrawal for prophylaxis).
  - Naloxone: 0.04–0.4mg IV (Opioids). Caution in chronic users (precipitates withdrawal).
Exposure: Remove clothes, wash skin (organophosphates).

3. diagnosis (toxidromes)

toxidrome	vital signs	pupils	skin	bowels	mental status	agents
Anticholinergic	$↑$ HR, $↑$ BP, $↑$ Temp	Dilated	Dry, Flushed	$↓$ Sounds	Delirium / Mumblings	TCAs, Antihistamines, Atropine
Sympathomimetic	$↑$ HR, $↑$ BP, $↑$ Temp	Dilated	Diaphoretic	$↑$ Sounds	Agitation / Psychosis	Cocaine, Amphetamines
Cholinergic	$\leftrightarrow$ HR, $\leftrightarrow$ BP	Pinpoint	Diaphoretic	$↑$ Sounds	Coma / Seizures	Organophosphates, Nerve Gas
Opioid	$↓$ HR, $↓$ BP, $↓$ RR	Pinpoint	Cool	$↓$ Sounds	CNS Depression	Heroin, Fentanyl, Oxycodone
Sedative-Hypnotic	$↓$ HR, $↓$ BP, $↓$ RR	Variable	Cool	$↓$ Sounds	CNS Depression	Benzos, Barbiturates, Alcohol

Distinguishing Anticholinergic vs. Sympathomimetic:

Both have $↑$ HR, $↑$ BP, and dilated pupils.

Anticholinergic: Dry skin (“Dry as a bone”).

Sympathomimetic: Sweaty skin.

4. interpretation of investigations

ECG: QRS prolongation (TCAs), QT prolongation (Antipsychotics, SSRIs), Ischaemia.
Blood Gas: Metabolic acidosis (MUDPILES), Respiratory alkalosis (Salicylates).
Anion Gap: $N a - (Cl + H C O_{3})$ . Normal: 10–12.
Osmolar Gap: $M e a s u re d O s m - C a l c u l a t e d O s m$ . Calculated $= 2 [N a] + Gl u cose + U re a + (1.25 \times EtO H)$ . Gap $> 10$ is abnormal (Toxic Alcohols).
Specific Levels: Acetaminophen (on all intentional ingestions), Salicylate, Ethanol, Lithium, Digoxin, Valproic Acid.

5. decontamination

Activated Charcoal (AC):
- Dose: 1g/kg (max 50g).
- Indication: Potentially toxic ingestion within 1 hour (up to 2-4h for delayed release or anticholinergics).
- Contraindications: Unprotected airway, bowel obstruction, hydrocarbons, caustics, metals (Lithium/Iron - doesn’t bind).
Whole Bowel Irrigation (PEG):
- Indications: Body packers, Iron, Lithium, Sustained-release preparations (e.g., CCB/BB).

6. enhanced elimination

Multiple Dose Activated Charcoal (MDAC):
- Indications: “ABCD” – Antimalarials (Quinine), Barbiturates, Carbamazepine, Dapsone (and Theophylline).
Urinary Alkalinisation:
- Goal: Urine pH 7.5–8.0.
- Indications: Salicylates, Methotrexate, Phenobarbital.
- Method: Sodium Bicarbonate infusion. Requires correction of Hypokalaemia.
Haemodialysis:
- Indications: I STUMBLE
  - I – Isoniazid / Isopropyl Alcohol (rarely needed)
  - S – Salicylates (Severe)
  - T – Theophylline
  - U – Uraemia
  - M – Methanol
  - B – Barbiturates
  - L – Lithium
  - E – Ethylene Glycol

7. summary

toxin / syndrome	key features / toxidrome	antidote/management (mechanism)
Anticholinergic	$↑$ HR/BP/Temp, Dilated Pupils, Dry Skin, Delirium.	Physostigmine (AChE inhibitor - consult tox), Supportive (Benzos).
Sympathomimetic	$↑$ HR/BP/Temp, Dilated Pupils, Diaphoretic, Agitation.	Benzodiazepines (GABA agonism), Cooling.
Cholinergic	Pinpoint Pupils, Diaphoretic, $↑$ Bowel Sounds, Salivation, Bradycardia.	Atropine (Muscarinic antagonist), Pralidoxime (Reactivates AChE).
Opioid	$↓$ HR/BP/RR, Pinpoint Pupils, CNS Depression.	Naloxone (Competitive Mu-antagonist).
Sedative-Hypnotic	$↓$ HR/BP/RR, CNS Depression.	Flumazenil (GABA antagonist - Caution: Seizures), Supportive.
Acetaminophen	NAPQI $\to$ Hepatic Necrosis. Rumack-Matthew Nomogram.	NAC / N-Acetylcysteine (Restores Glutathione).
Salicylates	Resp Alk + Met Acidosis. Tinnitus. Hyperthermia.	Urine Alkalinisation (Ion trapping), Dialysis.
Toxic Alcohols	Osmolar Gap $\to$ Anion Gap. Blindness (Methanol) / Renal (EG).	Fomepizole (ADH Inhibition), Dialysis.
Tricyclic Antidepressants (TCA)	Wide QRS, Anticholinergic, Hypotension.	Sodium Bicarbonate (Overcomes Na-channel blockade).
Lithium	Tremor, Confusion. Precipitated by dehydration/AKI.	Fluids, Dialysis (Enhanced elimination).
Carbon Monoxide & Cyanide	Fires. CO: Normal SpO2. CN: High Lactate.	CO: 100% O2 / Hyperbaric (Competes for Hb). CN: Hydroxocobalamin (Chelation / B12 formation).
Methemoglobinaemia	”Chocolate Blood”. Saturation Gap.	Methylene Blue (Reducing agent - NADPH dependent).
Hyperthermic Toxidromes	Serotonin: Clonus, Hyperreflexia. NMS: Rigidity (“Lead pipe”).	Serotonin: Benzos, Cyproheptadine (5-HT antagonist). NMS: Bromocriptine (DA agonist), Dantrolene.
Digoxin	Bradycardia, Hyperkalaemia, “Scooped” ST segments.	DigiFab (Antibody fragments).
Beta-Blockers	Bradycardia, Shock, Hypoglycaemia.	Glucagon (cAMP), High Dose Insulin (Metabolic support), Calcium.
CCB	Bradycardia, Shock, Hyperglycaemia.	Calcium (Inotropy), High Dose Insulin (Metabolic support), Lipids.
Isoniazid	Seizures (refractory to benzos), AG Metabolic Acidosis.	Pyridoxine / Vit B6 (Restores GABA synthesis).
Sulfonylurea	Profound Hypoglycaemia.	Octreotide (Inhibits insulin release), Dextrose.
Valproic Acid	Hyperammonaemia, Hepatotoxicity.	L-Carnitine (Mitochondrial support).
Local Anaesthetics	CNS excitation, Cardiac arrest (LAST).	Intralipid (Lipid sink).

Explorer

admittomedicine

toxicology

approach to the poisoned patient

1. history & physical

history

physical

stat investigations

2. resuscitation (abcde)

3. diagnosis (toxidromes)

4. interpretation of investigations

5. decontamination

6. enhanced elimination

7. summary

tricyclic antidepressants (tca)

acetaminophen (paracetamol)

carbon monoxide & cyanide

hyperthermic toxidromes

lithium toxicity

methemoglobinaemia

salicylates (aspirin)

toxic alcohols (methanol & ethylene glycol)