managing-toxicology-emergencies

# Managing Toxicology Emergencies

Identifies classic toxidromes through systematic physical examination, guides GI decontamination decisions, and directs specific antidote protocols with dosing, monitoring, and poison center coordination.

## Why This Skill Exists

Poisoning is the leading cause of injury death in the United States, surpassing motor vehicle crashes. The American Association of Poison Control Centers receives 2.1 million calls annually. Emergency physicians must rapidly identify toxidromes—characteristic constellations of signs that point to a drug class—because specific antidotes exist for many common poisonings and the window for effective treatment is narrow. N-acetylcysteine for acetaminophen is most effective within 8 hours. Digoxin-specific antibody fragments reverse life-threatening dysrhythmias within minutes. Delayed recognition of a toxic alcohol ingestion (methanol, ethylene glycol) allows irreversible end-organ damage.

Decontamination decisions (activated charcoal, whole bowel irrigation, gastric lavage) are time-sensitive and often misapplied. This skill provides the evidence-based framework for each intervention based on substance, timing, clinical status, and airway protection.

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## Checkpoint A: Pre-Draft Intake (Mandatory)

1. What substance(s) was/were ingested, inhaled, or exposed to? (Name, formulation, amount if known)
2. What was the time of exposure relative to current presentation?
3. Was the exposure intentional (suicide attempt) or unintentional (accidental, pediatric exploratory, therapeutic error)?
4. What are the current vital signs, mental status (GCS), and pupil examination findings?
5. Does the patient have co-ingestants or polypharmacy exposure?
6. What was the route of exposure (oral, inhalation, dermal, IV, ocular)?
7. Has the patient vomited, and has any decontamination been performed in the field?
8. Is the patient pregnant?

### Documents to Request

- Pill bottles, medication blister packs, or product containers (photograph and retain)
- Pharmacy fill records (query state PDMP)
- EMS run sheet with field vital signs and treatments
- Prior toxicology encounters and psychiatric history
- Serum and urine drug levels (acetaminophen, salicylate, ethanol, toxic alcohols)
- ECG (QRS width, QTc interval, rhythm)
- Basic metabolic panel with calculated anion gap and osmolar gap
- Arterial blood gas if respiratory/metabolic derangement suspected
- Poison Control Center consultation documentation

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## Step 1: Toxidrome Identification

### Classic Toxidromes

| Toxidrome | Pupils | HR | BP | Temp | Skin | Mental Status | Other | Agents |
|---|---|---|---|---|---|---|---|---|
| Sympathomimetic | Dilated | ↑ | ↑ | ↑ | Diaphoretic | Agitated | Tremor, seizures | Cocaine, amphetamines, MDMA |
| Anticholinergic | Dilated | ↑ | ↑ | ↑ | Dry, flushed | Delirious, hallucinating | Urinary retention, absent bowel sounds | Antihistamines, TCAs, jimsonweed |
| Cholinergic | Constricted | ↓ or ↑ | Variable | Normal | Diaphoretic | Confused | SLUDGE/BBB (Salivation, Lacrimation, Urination, Defecation, GI upset, Emesis / Bradycardia, Bronchorrhea, Bronchospasm) | Organophosphates, carbamates, nerve agents |
| Opioid | Constricted (pinpoint) | ↓ | ↓ | ↓ | Normal | CNS depression/coma | Respiratory depression, decreased bowel sounds | Heroin, fentanyl, morphine, methadone |
| Sedative-Hypnotic | Normal or miotic | ↓ | ↓ | ↓ | Normal | CNS depression | Hyporeflexia, respiratory depression | Benzodiazepines, barbiturates, GHB |
| Serotonin Syndrome | Dilated | ↑ | ↑ | ↑ | Diaphoretic | Agitated, confused | Clonus (especially ocular), hyperreflexia, rigidity | SSRIs + MAOIs, tramadol, linezolid |

**Mnemonic for anticholinergic**: "Blind as a bat (mydriasis), mad as a hatter (delirium), red as a beet (flushing), hot as a hare (hyperthermia), dry as a bone (anhidrosis), full as a flask (urinary retention), the heart runs alone (tachycardia)."

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## Step 2: Universal Toxicology Workup

Order for every intentional ingestion or unknown overdose:

1. **Serum acetaminophen level** (regardless of reported ingestion—occult co-ingestion found in 5-10%)
2. **Serum salicylate level** (frequently co-ingested, often missed)
3. **Serum ethanol level**
4. **Basic metabolic panel** with anion gap calculation: AG = Na - (Cl + HCO3); normal 8-12
5. **Serum osmolality** (measured) and osmolar gap calculation: OG = measured osmolality - calculated osmolality; normal <10
6. **12-lead ECG**: QRS >100 ms (sodium channel blockade: TCAs, cocaine), QTc >500 ms (risk of torsades)
7. **Arterial or venous blood gas**
8. **Pregnancy test** for all women of childbearing age
9. **Urinalysis** for crystals (calcium oxalate = ethylene glycol)
10. **Urine drug screen** (qualitative, many false positives/negatives—use for context, not definitive diagnosis)

### Anion Gap and Osmolar Gap Differential

**Elevated anion gap metabolic acidosis (GOLDMARK)**: Glycols (ethylene glycol), Oxoproline (acetaminophen chronic), L-lactate, D-lactate, Methanol, Aspirin (salicylates), Renal failure, Ketoacidosis

**Elevated osmolar gap**: Methanol, Ethylene glycol, Isopropyl alcohol, Ethanol, Propylene glycol, Acetone

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## Step 3: Decontamination Decisions

| Method | Indication | Contraindications | Time Window |
|---|---|---|---|
| Activated charcoal (1 g/kg, max 50 g) | Potentially toxic ingestion of adsorbable substance | Unprotected airway, caustic ingestion, hydrocarbons, metals (lithium, iron, potassium), ileus | Most effective <1 hour; limited benefit >2 hours |
| Whole bowel irrigation (GoLYTELY 2 L/hr) | Sustained-release preparations, body packers, iron, lithium | Unprotected airway, ileus, bowel obstruction, perforation | Until clear rectal effluent |
| Gastric lavage (rarely indicated) | Massive life-threatening ingestion presenting within 1 hour | Unprotected airway, caustics, hydrocarbons, sharp objects | <1 hour and only if substance is life-threatening and not adsorbable |
| Skin decontamination | Organophosphate, chemical exposure | None (always decontaminate) | Immediately |
| Eye irrigation | Chemical splash, caustic exposure | None | Immediately, continuous until pH neutral (check at 30 min) |

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## Step 4: Specific Antidotes

| Toxin | Antidote | Dose | Key Monitoring |
|---|---|---|---|
| Acetaminophen | N-acetylcysteine (NAC) | 150 mg/kg IV over 1 hr, then 50 mg/kg over 4 hr, then 100 mg/kg over 16 hr (21-hour protocol) | APAP levels, LFTs, INR q4-6h; anaphylactoid reactions to NAC |
| Opioids | Naloxone | 0.04-0.4 mg IV titrated (start low to avoid full reversal and withdrawal) | Respiratory rate, mental status; redose q2-3 min; half-life shorter than most opioids—observe for renarcotization |
| Benzodiazepines | Flumazenil | 0.2 mg IV over 30 sec; repeat 0.3 mg then 0.5 mg q1min (max 3 mg) | Contraindicated if chronic BZD use, seizure history, TCA co-ingestion—may precipitate seizures |
| Beta-blockers | Glucagon | 3-5 mg IV bolus, then 2-10 mg/hr infusion | Nausea/vomiting common; high-dose insulin euglycemic therapy as alternative |
| Calcium channel blockers | High-dose insulin (HDI) | 1 unit/kg IV bolus + 1-10 units/kg/hr infusion | Dextrose 50% to maintain glucose >150; K+ monitoring q30-60 min |
| Digoxin | Digoxin-specific Fab (DigiFab) | Empiric 10-20 vials for acute life-threatening; calculate by level or amount ingested | Monitor K+ (will shift as dig effect reverses); cardiac monitoring |
| Organophosphates | Atropine + Pralidoxime | Atropine 2-4 mg IV q5-10 min until bronchorrhea clears; pralidoxime 1-2 g IV over 30 min | Titrate to secretion drying, NOT to pupil size or heart rate |
| Methanol/Ethylene glycol | Fomepizole | 15 mg/kg IV load, then 10 mg/kg q12h x 4, then 15 mg/kg q12h | Osmolar gap, anion gap, pH; hemodialysis if pH <7.25, renal failure, visual symptoms, or level >50 |
| TCAs (sodium channel blockade) | Sodium bicarbonate | 1-2 mEq/kg IV bolus; repeat until QRS <120 ms; infusion 150 mEq in 1L D5W | Continuous cardiac monitor; target serum pH 7.50-7.55 |
| Iron | Deferoxamine | 15 mg/kg/hr IV (max 6-8 g/day) | Urine color (vin rosé); hypotension; ARDS with prolonged use >24h |
| Cyanide | Hydroxocobalamin | 5 g IV over 15 min (adult); may repeat | Do not delay for confirmation; interference with lab colorimetric assays |

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## Step 5: Disposition and Observation

| Scenario | Disposition | Duration |
|---|---|---|
| Known non-toxic ingestion confirmed | Discharge after psychiatric screening if intentional | Medical clearance then psych eval |
| Asymptomatic with potentially toxic ingestion | Observation for duration of expected peak effect | Substance-specific (4h for IR, 12-24h for SR) |
| Symptomatic requiring antidote | ICU admission | Until clinically stable and antidote course complete |
| Acetaminophen with NAC protocol | Observation or floor admission | 21-hour IV protocol minimum; extend if LFTs rising |

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## Checkpoint B: Post-Draft Alignment (Mandatory)

1. Was a toxidrome identified or systematically excluded through physical examination findings?
2. Were acetaminophen and salicylate levels obtained regardless of reported ingestion?
3. Was the decontamination decision evidence-based with timing and contraindications documented?
4. Are antidote doses, timing, monitoring parameters, and endpoints documented?
5. Was Poison Control consulted and the case number documented?

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## Quality Audit

| # | Criterion | Pass/Fail |
|---|---|---|
| 1 | Toxidrome identification attempted with documented physical exam | |
| 2 | Acetaminophen and salicylate levels obtained | |
| 3 | ECG obtained with QRS and QTc measurements documented | |
| 4 | Anion gap calculated and documented | |
| 5 | Osmolar gap calculated when toxic alcohol suspected | |
| 6 | Decontamination decision documented with rationale | |
| 7 | Antidote selection, dose, route, and timing documented | |
| 8 | Poison Control consulted with case number recorded | |
| 9 | Psychiatric evaluation completed for intentional ingestions | |
| 10 | Observation duration appropriate for substance and formulation | |
| 11 | Serial lab monitoring ordered for evolving toxicity | |
| 12 | Pregnancy test obtained for women of childbearing age | |
| 13 | PDMP queried for suspected prescription drug abuse | |

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## Guidelines

1. **Always check acetaminophen and salicylate levels** in any intentional ingestion—these are the most common occult co-ingestants and both have specific, time-sensitive antidotes
2. **The urine drug screen is a screening tool, not a diagnostic test**—false positives (dextromethorphan for PCP, sertraline for benzodiazepines) and false negatives (fentanyl analogs, many synthetic opioids) are common
3. **Start low with naloxone (0.04-0.1 mg)** in suspected opioid-dependent patients—full reversal with 2 mg causes immediate withdrawal with projectile vomiting (aspiration risk), agitation, and patient elopement
4. **Activated charcoal should NOT be given routinely**—it is only beneficial within 1-2 hours, the substance must be adsorbable, and the airway must be protected; forced administration increases aspiration risk
5. **Sodium bicarbonate for wide-complex tachycardia** from sodium channel blockade (TCAs, class IC antiarrhythmics) is a life-saving intervention—do not wait for toxicology confirmation; treat the ECG
6. **QTc >500 ms requires continuous monitoring** and correction of hypokalemia and hypomagnesemia—avoid additional QT-prolonging medications including ondansetron and haloperidol
7. **High-dose insulin therapy** for calcium channel blocker and beta-blocker overdose is underutilized—doses of 1-10 units/kg/hr with glucose supplementation are safe and effective when vasopressors fail
8. **Fomepizole has replaced ethanol** as the preferred antidote for toxic alcohol poisoning—it has a cleaner side effect profile, does not require ICU monitoring for intoxication, and is easier to dose