Agitation and Hypoxia After a Fall: Delirium or Something Else?
An 81-year-old man with mild cognitive impairment, atrial fibrillation on apixaban, and osteoarthritis is admitted after a mechanical fall with a negative head CT and no fracture. On hospital day 2 he becomes acutely agitated, pulling at lines, with fluctuating attention. Vitals: T 37.9 C, HR 118 irregular, BP 156/88, RR 24, SpO2 91% on room air. He was started on oxycodone for hip pain and diphenhydramine for sleep, and has not had a bowel movement in 3 days. Exam: bibasilar crackles, distended tympanic abdomen, dry mucous membranes, mild right leg swelling compared with the left. Labs: Na 149, K 4.2, BUN 44, creatinine 1.4 (baseline 1.0), glucose 190, WBC 11.2, lactate 1.8. ECG shows atrial fibrillation at 118 with no acute ischemic changes.
1. Build a structured differential for the acute change in mental status using a mnemonic-based framework, and identify which elements of this case are iatrogenic and modifiable.
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Framework (e.g., DELIRIUM / 'DIMES'):
- D - Drugs: oxycodone (opioid), diphenhydramine (anticholinergic), apixaban (bleeding risk).
- I - Infection: T 37.9, WBC 11.2, crackles → aspiration pneumonia, UTI.
- M - Metabolic: Na 149 (hypernatremia from poor intake), rising creatinine (AKI), glucose 190; check Ca, ammonia, TSH.
- E - Environment/withdrawal: new ward, restraints, sleep disruption; alcohol/benzodiazepine withdrawal history must be sought.
- S - Structural/Seizure/Stroke: fall with anticoagulation - even a negative initial CT does not exclude delayed intracranial hemorrhage; consider repeat imaging if neuro exam changes. AF with rapid ventricular response can cause hypoperfusion.
Iatrogenic and modifiable: oxycodone (opioid-induced delirium/constipation), diphenhydramine (strongly anticholinergic - avoid in older adults), and the resulting constipation/ileus. The distended tympanic abdomen plus 3 days without a bowel movement makes fecal impaction/ileus a real contributor to agitation.
Non-modifiable/needing workup: hypoxia (SpO2 91%) and possible aspiration, AKI, hypernatremia, uncontrolled AF rate, unilateral leg swelling raising concern for DVT/PE (hypoxia, tachycardia).
Key principle: delirium in older adults is usually multifactorial - treat all contributors, not one.
2. Prioritize your first-hour actions and specify the medication changes you would make, with rationale for each.
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First hour (ABCs and reversible causes):
- Oxygen to keep SpO2 ≥92–94%; obtain ABG/VBG and consider chest imaging for aspiration.
- Assess volume and perfusion - dry mucous membranes, rising creatinine, hypernatremia → give cautious isotonic fluid (she/he is volume-depleted; correct Na slowly, no faster than ~8–10 mmol/L/day).
- Rate control - AF at 118 in a hypoxic, delirious patient: treat the trigger (hypoxia, infection, pain, volume) and use a short-acting agent (IV metoprolol or diltiazem if BP permits) with target HR <110–120; avoid over-aggressive rate control that worsens perfusion.
- Constipation/ileus - abdominal exam, consider imaging, discontinue constipating agents, treat impaction; this is often overlooked as a delirium driver.
- Delirium non-pharmacologic bundle - reorientation, sleep hygiene, glasses/hearing aids, early mobility, family presence; avoid restraints.
Medication changes:
- Stop diphenhydramine - strongly anticholinergic, Beers-listed, worsens delirium and urinary retention.
- Reduce/stop oxycodone - opioid contributes to delirium and ileus; use multimodal analgesia (acetaminophen, topical, nerve block) and add a bowel regimen.
- Avoid antipsychotics as first-line - reserve low-dose antipsychotic only for dangerous agitation not responding to non-drug measures, and only briefly; they do not treat delirium and prolong QT.
- Continue apixaban unless bleeding is identified; if any neuro decline, repeat head CT before assuming delirium.
Monitoring: repeat electrolytes/creatinine, glucose, telemetry, and reassess mental status with a validated tool (CAM) each shift.