What systematic history should be obtained when evaluating a patient with suspected poisoning?

History Taking for Poisoning Cases

When evaluating a patient with suspected poisoning, obtain a systematic history that prioritizes identifying life-threatening conditions, determining the specific toxin and dose, assessing suicide risk, and gathering information that directly impacts morbidity and mortality through timely intervention.

Immediate Assessment of Life-Threatening Conditions

First, rapidly assess for conditions requiring immediate intervention before detailed history taking:

• Evaluate airway patency, breathing adequacy, and circulatory status, as airway compromise from laryngeal edema or aspiration can develop rapidly and is a leading cause of early mortality in poisoning cases 1
• Identify signs of severe toxicity including altered mental status, seizures, severe bradycardia, hypotension, respiratory depression, or cardiovascular instability that require immediate stabilization 2, 3
• Document vital signs immediately, as abnormalities guide both diagnosis and urgency of intervention 2

Essential Historical Elements

Substance Identification

Determine the specific agent(s) involved with maximum precision:

• Identify the exact name, formulation, concentration, and physical form of the substance ingested 1, 4
• For medication poisoning, obtain the specific drug name, strength, and whether it is immediate-release or extended-release formulation 4, 5
• Bring all pill bottles, containers, or packaging to the emergency department for verification, as patient history alone is unreliable 6
• For corrosive ingestions, identify whether the substance is acid or alkali, as management differs significantly 1

Dose and Timing

Quantify exposure with specificity:

• Calculate the maximum possible dose ingested in mg/kg body weight 4, 5
• Document the exact time of ingestion, as this determines the window for decontamination and predicts symptom onset 3, 5
• For chronic exposures, determine the duration and pattern of exposure 5
• Recognize that reported doses may be imprecise and require complementary confirmation from clinical findings or laboratory testing 7

Intent Assessment

Determine whether ingestion was intentional or accidental, as this fundamentally changes management:

• Patients with suspected self-harm or victims of malicious administration should be referred to an emergency department immediately regardless of dose 4, 5
• All patients with intentional ingestion require mandatory psychiatric evaluation and follow-up, as they have high risk of repeat suicide attempts 7, 1
• Massive suicidal ingestions in adults typically cause more severe injury than accidental pediatric exposures 1

Co-Ingestions and Comorbidities

Identify factors that modify toxicity:

• Document all co-ingested substances including alcohol, other medications, or illicit drugs, as combined toxicities alter management 4, 5
• Identify underlying cardiovascular or neurological disease, as these conditions warrant emergency department referral at lower doses than for other individuals 4
• For pregnant patients in the last trimester, special evaluation of maternal and fetal risk is required 5

Symptom Assessment

Systematically evaluate for toxidrome features and organ-specific toxicity:

• Document neurological symptoms: altered mental status, confusion, lethargy, seizures, tremor, agitation, or coma 2, 3, 5
• Assess cardiovascular symptoms: chest pain, palpitations, dyspnea, or syncope 2
• Evaluate gastrointestinal symptoms: nausea, vomiting, hematemesis, abdominal pain, or diarrhea 5
• Identify respiratory symptoms: tachypnea, hyperpnea, dyspnea, or respiratory depression 3, 5
• For specific toxins, assess characteristic symptoms: tinnitus and deafness for salicylates 5, stridor and hoarseness for corrosive ingestions 1

Environmental and Exposure Context

Gather information about the poisoning environment:

• For carbon monoxide poisoning, identify the exposure source and measure ambient CO levels if possible, as elevated levels confirm poisoning 7
• Determine if other individuals were exposed in the same environment, as simultaneously exposed symptomatic persons may not require COHb measurement if one person has documented elevation 7
• For corrosive exposures, determine the location and circumstances of exposure to assess contamination risk 1

Critical Pitfalls to Avoid

Common errors in history taking that compromise outcomes:

• Do not rely solely on patient-reported substance or dose, as only 83.6% of patient histories match systematic toxicological analysis results, and 8.4% of patients do not report substances they actually ingested 6
• Do not assume absence of oral lesions excludes significant gastrointestinal injury in corrosive poisoning, as clinical symptoms and oral lesions do not correlate reliably with internal damage 1
• Do not delay supportive care while obtaining detailed history, as clinical presentation is diagnostic and immediate intervention reduces morbidity and mortality 8, 3
• For asymptomatic patients, recognize that symptoms may be delayed: monitor for approximately 12 hours after non-enteric-coated salicylate ingestion and 24 hours after enteric-coated aspirin 5

Immediate Actions During History Taking

While obtaining history, simultaneously initiate critical interventions:

• Contact the Poison Control Center immediately (US: 1-800-222-1222) for expert guidance on agent-specific management and systemic toxicity evaluation 1, 9, 8, 2
• Administer 100% oxygen to any patient with suspected carbon monoxide poisoning while awaiting confirmation 7
• Obtain ECG for patients with chest pain, dyspnea, or overdoses of beta blockers, tricyclic antidepressants, or antidysrhythmics 2, 4
• Measure electrolytes, serum creatinine, bicarbonate, and calculate anion gap based on clinical presentation 2