Toxicology and Overdose Management — Part 1: General Approach, Toxidrome Recognition & GI Decontamination

1. Initial Approach to the Poisoned Patient

1.1 Scene Safety and Information Gathering

The initial assessment of a poisoned patient begins with simultaneous stabilization and information gathering. Critical data sources include emergency medical services personnel, family members, pill bottles or containers found at the scene, pharmacy records, and the patient’s own report when obtainable. However, the history in overdose is notoriously unreliable — the agent, quantity, timing, and intent reported by the patient may all be inaccurate. Clinical decision-making should therefore be guided primarily by the physical examination and objective findings rather than history alone.¹

Key historical data to obtain when possible:

• What substance(s) — request pill bottles, containers, photographs from scene
• How much — maximum potential ingestion (assume worst case)
• When — time of ingestion relative to presentation
• Route — oral, intravenous, inhalational, dermal, rectal, ophthalmic
• Why — intentional (suicidal, recreational, assault) versus unintentional (therapeutic error, pediatric exploratory)
• Co-ingestants — always assume multiple agents in intentional overdose
• Vomiting — spontaneous emesis may reduce absorbed dose
• Medical history — baseline medications, organ dysfunction, psychiatric history

1.2 Primary Stabilization: The “ABCDs” of Toxicology

The initial management of the poisoned patient follows the standard resuscitation framework with toxicology-specific modifications:^{1 2}

A — Airway:

• Assess patency and protective reflexes (gag, cough, swallow)
• Endotracheal intubation for GCS ≤ 8 or loss of protective reflexes
• Avoid succinylcholine if hyperkalemia is suspected (e.g., digoxin, massive tissue necrosis)
• Rapid sequence intubation with rocuronium is preferred in most toxicologic emergencies

B — Breathing:

• Apply supplemental oxygen; obtain continuous pulse oximetry
• Note respiratory rate and pattern: tachypnea may indicate salicylate, metabolic acidosis, or sympathomimetic toxicity; bradypnea suggests opioids, sedative-hypnotics, or clonidine
• Monitor for respiratory failure requiring mechanical ventilation

C — Circulation:

• Obtain IV access (two large-bore peripheral lines)
• Continuous cardiac monitoring — attach 12-lead ECG as soon as feasible
• Treat hypotension with isotonic crystalloid boluses initially (20 mL/kg)
• Vasopressors as needed — norepinephrine is first-line for most toxicologic shock
• Treat specific arrhythmias based on suspected toxin (sodium bicarbonate for wide-QRS, calcium for hyperkalemia)

D — Disability and Dextrose:

• Check point-of-care blood glucose immediately on all altered patients
• Dextrose: 50 mL of D50W (25 g) IV for confirmed or suspected hypoglycemia — do not withhold for fear of Wernicke encephalopathy; thiamine does not need to precede dextrose
• Naloxone: For suspected opioid toxicity (respiratory depression, miosis, decreased level of consciousness) — see Section 1.3
• Thiamine: 100 mg IV for at-risk patients (chronic alcohol use, malnourishment)
• Obtain rapid neurologic assessment (GCS, pupil size and reactivity, focal deficits)

E — Exposure and Environmental:

• Full body examination; remove all clothing
• Check skin temperature, presence of diaphoresis or dry skin
• Examine for needle tracks, transdermal patches, pill fragments in mouth
• Decontaminate skin if dermal exposure (organophosphates, hydrofluoric acid, chemical agents)

1.3 Naloxone Decision Algorithm

Naloxone (naloxone hydrochloride) is a pure competitive opioid antagonist at mu, kappa, and delta receptors. Its use in the emergency department requires a thoughtful, titrated approach:³

Indications:

• Clinical triad of respiratory depression (rate < 12/min), miosis, and decreased level of consciousness consistent with opioid toxicity
• Do NOT use pupil size alone — mydriasis can occur with co-ingestants, hypoxia, or certain synthetic opioids

Dosing — Titrate to respiratory effort, NOT full consciousness:

• Repeat doses every 2–3 minutes as needed
• Goal: restore adequate spontaneous ventilation (rate > 12/min), NOT full alertness
• If no response after 10 mg total, reconsider diagnosis — opioid toxicity is unlikely

Naloxone Infusion:

• Indicated when repeated boluses are required (long-acting opioids: methadone, extended-release formulations)
• Rate: two-thirds of the effective bolus dose per hour in continuous IV infusion
• Example: if 2 mg was required to restore breathing, infuse at 1.3 mg/hr
• Mix in normal saline or D5W; titrate to maintain adequate respiration

Observation Periods After Naloxone:

2. Toxidrome Recognition

Toxidromes are constellations of clinical signs and symptoms that suggest a class of poisoning. Accurate toxidrome recognition is one of the most valuable skills in clinical toxicology, as it allows the clinician to direct management even before specific agent identification.^{1 2}

2.1 Major Toxidromes — Complete Reference Table

2.2 Distinguishing Sympathomimetic from Anticholinergic Toxidrome

These two toxidromes share tachycardia, hypertension, hyperthermia, mydriasis, and altered mental status. The key distinguishing feature is skin moisture:

2.3 Distinguishing Serotonin Syndrome from NMS

3. Diagnostic Workup in the Poisoned Patient

3.1 Universal Screening — Every Overdose Patient

Certain laboratory studies should be obtained on every patient presenting with suspected poisoning or intentional overdose, regardless of the reported ingestion:^{1 2 4}

Mandatory studies:

Additional studies based on clinical scenario:

3.2 The Urine Drug Screen — Limitations

The urine drug screen (UDS) is one of the most commonly ordered and most commonly misinterpreted tests in toxicology. Clinicians must understand its significant limitations:^{1 5}

Critical limitations:

Bottom line: The urine drug screen should never delay treatment and should never be the sole basis for clinical decision-making. It may have value for confirming suspected exposure or for documentation, but it does not direct acute management.

3.3 Anion Gap and Osmol Gap

Anion Gap

The serum anion gap (AG) is a critical tool in the evaluation of metabolic acidosis in the poisoned patient.¹

Calculation: AG = Na⁺ − (Cl⁻ + HCO₃⁻)

Normal: 8–12 mEq/L (varies by laboratory; albumin-corrected: add 2.5 for each 1 g/dL albumin below 4.0)

Elevated anion gap metabolic acidosis (AGMA) — Toxicologic causes (mnemonic: CAT MUDPILES):

Osmol Gap

The osmol gap is essential for evaluating suspected toxic alcohol ingestion.^{1 6}

Calculation:

• Calculated osmolality = 2(Na⁺) + (BUN/2.8) + (Glucose/18) + (Ethanol/4.6)
• Osmol gap = Measured osmolality − Calculated osmolality

Normal: < 10 mOsm/kg (some references use < 14)

Elevated osmol gap — Toxicologic causes:

Important caveat: A normal osmol gap does NOT exclude toxic alcohol poisoning. Once the parent alcohol is metabolized to its toxic metabolites (formic acid from methanol, glycolic and oxalic acids from ethylene glycol), the osmol gap normalizes while the anion gap rises. In late presentations, the osmol gap may be normal with a profoundly elevated anion gap.

4. Gastrointestinal Decontamination

4.1 Activated Charcoal — Single Dose

Activated charcoal (AC) is the most commonly used gastrointestinal decontamination modality. It acts by adsorbing ingested substances within the GI tract, reducing bioavailability. The surface area of activated charcoal is approximately 950–2,000 m² per gram, providing extensive adsorptive capacity.^{7 8}

Dosing

Optimal timing: Within 1 hour of ingestion for greatest benefit; consider up to 2 hours for agents with slower absorption. Extended window (up to 4 hours or beyond) may be appropriate for:

• Agents that slow gastric emptying (anticholinergics, opioids)
• Large ingestions forming bezoars
• Sustained-release or enteric-coated formulations
• Agents with continued absorption (e.g., massive ingestions)

Substances NOT Adsorbed by Activated Charcoal

Mnemonic: PHAILS

Additional agents not well adsorbed: potassium, sodium, fluoride, caustics (acids and alkalis).

Contraindications

Adverse Effects

• Vomiting (most common, 5–20% of patients)
• Aspiration pneumonitis or pneumonia (rare but most serious complication)
• Constipation
• Corneal abrasion if contact with eyes
• Charcoal bezoar (rare, primarily with repeated dosing)

4.2 Whole Bowel Irrigation (WBI)

Whole bowel irrigation involves the enteral administration of large volumes of polyethylene glycol–electrolyte lavage solution (PEG-ELS, e.g., GoLYTELY) to mechanically flush the GI tract and reduce absorption of ingested substances.⁹

Dosing

Continue until: rectal effluent is clear, typically requiring 4–6 hours in adults.

Indications

Contraindications

• Unprotected airway
• Hemodynamic instability
• Intractable vomiting
• GI hemorrhage, obstruction, ileus, or perforation
• Caustic ingestion

4.3 Gastric Lavage

Gastric lavage (stomach pumping) involves the insertion of a large-bore orogastric tube (36–40 French in adults, 24–28 French in children) and repeated instillation and aspiration of aliquots of fluid to remove gastric contents.¹⁰

Current status: Gastric lavage is rarely indicated and should NOT be performed routinely. The evidence does not support improved clinical outcomes, and the procedure carries significant risks.

Rare Situations Where Gastric Lavage MAY Be Considered

• Life-threatening ingestion
• Presentation within 1 hour of ingestion
• Agent is highly toxic and not well adsorbed by charcoal (e.g., massive iron ingestion)
• Expected clinical deterioration is rapid

Technique (When Performed)

1. Ensure airway protection — intubate if altered mental status
2. Place patient in left lateral decubitus, head down (Trendelenburg)
3. Confirm orogastric tube position
4. Instill 200–300 mL aliquots of warm (37°C) normal saline or tap water in adults (10–15 mL/kg per aliquot in children)
5. Aspirate between each instillation
6. Continue until return is clear (typically 2–3 liters total)
7. Consider instilling activated charcoal through the tube before removal (if substance is adsorbed by AC)

Complications

• Aspiration pneumonitis/pneumonia
• Esophageal or gastric perforation
• Laryngospasm
• Hypothermia (if room-temperature fluid used)
• Electrolyte disturbances (with excessive tap water use)
• Mechanical injury to oropharynx

Contraindications

• Caustic ingestion (risk of perforation)
• Hydrocarbon ingestion (risk of aspiration)
• Unprotected airway (unless intubated)
• Small or sharp foreign bodies
• Presentation > 1 hour after ingestion (diminishing returns)

4.4 Multi-Dose Activated Charcoal (MDAC)

Multi-dose activated charcoal involves the administration of repeated doses of activated charcoal after the initial dose to enhance drug elimination. MDAC works by two mechanisms: (1) continued adsorption of drug still in the GI lumen (particularly with sustained-release formulations or agents that slow gastric motility), and (2) “gastrointestinal dialysis” — the creation of a concentration gradient across the gut mucosa that draws drug from the bloodstream back into the intestinal lumen, where it is adsorbed by charcoal.¹¹

Dosing Protocol

Established Indications for MDAC

The following substances have evidence supporting enhanced elimination by MDAC:¹¹

Other agents where MDAC may be considered: salicylates (large ingestion with rising levels), amlodipine (sustained-release), methotrexate.

Monitoring During MDAC

• Ensure intact or protected airway at all times
• Monitor for vomiting (aspiration risk) — consider antiemetic (ondansetron 4 mg IV)
• Assess bowel sounds regularly — discontinue if ileus develops
• Monitor electrolytes if prolonged course

Complications of MDAC

• Aspiration (greatest risk)
• Charcoal bezoar or intestinal obstruction (rare)
• Constipation
• Emesis

5. Poison Center Consultation

5.1 United States Poison Help Line

1-800-222-1222 — This single nationwide toll-free number connects callers to the regional poison center serving their area. Poison centers are staffed 24 hours a day, 7 days a week by specialists in poison information (SPIs), typically pharmacists or nurses with specialized toxicology training, and medical toxicologists.¹²

5.2 When to Call the Poison Center

• Any patient presenting with suspected poisoning, if clinical uncertainty exists
• Identification of unknown substances
• Guidance on decontamination strategies
• Antidote dosing and availability
• Disposition decision-making
• Confirmation that observation period is adequate before discharge
• Industrial chemical or hazardous material exposure
• Biological or chemical terrorism agent exposure

5.3 Toxicology Consultation

Formal medical toxicology consultation (bedside or telephone) should be obtained for:

• Life-threatening poisonings
• Need for hemodialysis or extracorporeal treatment
• Antidote use beyond routine naloxone/NAC
• Envenomation (snake, spider, marine)
• Poisoning in pregnancy
• Patients requiring ICU-level care for toxicologic reasons
• Unusual or unfamiliar substances
• Mass casualty events with toxic exposure

6. Disposition Decision Framework

6.1 Observation Period Considerations

The observation period after an acute ingestion depends on the agent’s pharmacokinetics, formulation (immediate-release versus sustained-release), and the clinical trajectory. General principles:¹

6.2 Criteria for ICU Admission

• Hemodynamic instability requiring vasopressors
• Intubation or respiratory support
• Need for specific infusions (sodium bicarbonate, high-dose insulin, lipid emulsion, naloxone, antivenom)
• QRS prolongation > 100 ms or significant arrhythmia
• Severe metabolic acidosis
• Hemodialysis requirement
• Altered mental status requiring frequent reassessment
• Ingestion of agents with known delayed deterioration

6.3 Psychiatric Evaluation

All patients with intentional self-harm require psychiatric evaluation before disposition. This evaluation should occur after the patient is:

• Medically cleared (toxicologic risk period has passed)
• Sober and at baseline mental status
• Able to meaningfully participate in risk assessment