2.1 Exposure History: The Questions That Change Management

The first official content area of the CSPI examination is history. That placement is deliberate. A specialist in poison information cannot examine the patient, cannot see the pill bottle, and cannot order a test. Every downstream decision - home observation versus referral, decontamination, antidote, laboratory timing, length of observation - rests on the quality of the history obtained by telephone.

This section builds that interrogation into a repeatable sequence, then covers the three high-yield exam themes: reconciling a history that conflicts with the findings, judging whether an account is plausible, and recognizing agents that hide behind a normal early examination.

The Core Data Set

Every human exposure case needs the same five elements before a disposition can be defended.

Turning Vague Answers into Numbers

• "Some pills are gone." Ask how many were dispensed, when the prescription was filled, and how many doses have been taken. Missing count = dispensed - (daily dose x days) - what remains.
• "A swallow of it." A young child's swallow is roughly 5 mL (about 10 mL in an older child and 15 mL in an adult). Use the larger plausible volume.
• "A little bit on the skin." Ask about surface area, concentration, occlusion by clothing or a diaper, and how long before rinsing.
• "He might have eaten a berry." Ask what the plant looks like, whether a specimen or photograph is available, whether any plant material is in the mouth, and how many children were present.

Worst-credible-dose rule: unless intact tablets or spilled liquid physically account for the difference, triage the case as though the missing amount was swallowed. A parent's guess reliably understates the exposure.

When the History and the Findings Disagree

One official objective asks the specialist to identify the causal agent when the symptoms and signs do not support the reported history. Physical findings outrank the narrative for three reasons: callers misidentify products, patients conceal intent, and co-ingestants go unmentioned.

Interrogation Repairs

1. Re-ask about access, not intent. "What medicines are in the house, including anyone visiting?" opens more cases than "Did he take anything else?"
2. Search the scene. Ask the caller to look in wastebaskets, toilets, under furniture, and in pockets and bags.
3. Ask about the container, not the drug. People remember bottle shape and color when they cannot recall a drug name.
4. Re-examine by proxy. Direct the caller or nurse to check the axillae for sweat, listen for bowel sounds, and palpate the bladder. Those three findings separate the two toxidromes that are otherwise identical.

Is the Account Plausible?

The blueprint asks the specialist to judge age-appropriate exposure scenarios. Development sets hard limits on what a child can do.

• A non-ambulatory infant cannot reach a shelf or open a cabinet. An exposure in a child younger than about 6 months was almost always administered by someone, whether by dosing error or otherwise.
• A toddler can open a purse, a pill organizer, or a drawer, and can defeat a child-resistant cap given enough time.
• A school-age child reports what happened; a sudden exposure story that keeps changing deserves a careful, non-accusatory second pass.
• Implausible accounts, injuries that do not match the story, repeat exposures in the same child, or a delay in seeking help raise concern for neglect or intentional administration. The specialist documents the facts objectively, keeps the tone non-judgmental, arranges medical evaluation, and follows the center's mandated-reporting policy.

Route-Specific Question Sets

Multiple victims or affected animals shift the assessment from an individual poisoning to a scene hazard: carbon monoxide from a generator or furnace, a chemical release, a mixed-cleaner reaction, or contaminated food.

Agents With a Quiet Early Window

The most dangerous sentence in a poison center is "he seems fine." The following exposures classically look normal for hours.

Acute, Chronic, and Acute-on-Chronic

Some drugs are more dangerous with repeated dosing than with a single large dose, because tissue stores accumulate.

• Lithium: chronic toxicity produces prominent neurologic findings at levels that look only modestly high, while an acute overdose in a lithium-naive patient may present with vomiting and a high level but little neurotoxicity at first.
• Digoxin: chronic accumulation (often with kidney injury, a diuretic, or an interacting drug) causes visual changes, delirium, and ventricular ectopy, frequently with hypokalemia, whereas acute overdose causes vomiting and hyperkalemia.
• Salicylate: chronic toxicity in older adults is routinely misdiagnosed as sepsis or delirium and carries higher mortality at lower levels than acute overdose.
• Vitamins A and D, iron, and theophylline likewise cause distinct chronic syndromes.

For these agents the specialist asks: how long has the patient been taking it, at what dose, what changed recently (illness, dehydration, a new prescription, a dose increase), and how is kidney function?

Practice Framework

1. Secure the callback number and location.
2. Screen for airway, breathing, circulation, consciousness, and seizures.
3. Identify the product in the caller's hand.
4. Convert the story into a worst-credible mg/kg dose.
5. Establish route and clock time.
6. Collect patient factors, including weight and chronic medications.
7. Ask what the patient looks like right now, and reconcile that with the story.
8. Decide disposition, then state the specific findings that should trigger an immediate call back.