Confusion / Delirium OSCE - Medication-Induced Confusion

Diagnosis: Medication-Induced Confusion

Case Overview

  • Age/Sex: 67-year-old male
  • Occupation: Retired accountant
  • Setting: Brought to ED by daughter from home
  • Chief complaint: "Confused and not themselves"

Patient Script

Who I Am

I’m a 67-year-old retired accountant who lives on my own; my daughter comes by a few times a week.

What Brings Me In

My daughter says I’ve been "not myself" for a few days — I don’t know where I am sometimes and I feel muddled.

My Story

For the last 3 days I’ve been feeling different — I’m more sleepy during the day, I’m mixing up what I’m doing, and I’ve had trouble remembering what I just said. My daughter noticed I seemed confused on Thursday, and today she brought me in because I got lost driving to the shops. I had some urinary urgency for a while and my GP started me on a new tablet for that 4 days ago; since then I’ve had a dry mouth, been constipated, and felt cloudy-headed. I haven’t had a fever or a bad cough. I did fall getting out of the shower about a week ago but I didn’t hurt myself. I sometimes take an over-the-counter sleep pill if I can’t get to sleep.

My Medical Background

  • Past medical history: hypertension, osteoarthritis, benign prostatic hyperplasia (BPH)
  • Regular medications: amlodipine, atorvastatin, tamsulosin (for BPH); I was started on a new bladder tablet 4 days ago
  • Over-the-counter: uses an antihistamine/diphenhydramine occasionally for sleep
  • Allergies: none known
  • Social: lives alone, daughter nearby; drinks 1–2 beers most evenings; no smoking
  • Family: mother had "memory problems" in old age

What I Think & Worry About

  • I think maybe I’m getting old and my memory is going — maybe it’s dementia.
  • I worry I might be a burden to my daughter or that I’ll have to move into a home.
  • I want to know if this is something that will get better and if it’s from the new pill I was given.

If You Ask Me About Other Symptoms...

  • "Do you have pain?" — I have my usual knee pain from arthritis, no new headache.
  • "Do you have fever or chills?" — No fever; I felt a bit clammy the other night but no high temperature.
  • "Any urinary symptoms?" — I had urgency and a bit of leakage for months; since the new tablet the urgency is less but sometimes it’s hard to start peeing.
  • "Any coughing, shortness of breath, or chest pain?" — No.
  • "Any recent infections, diarrhoea, vomiting?" — No.
  • "Any new medicines besides the bladder pill?" — No, just the occasional sleep antihistamine when I can’t sleep.

Clinical Summary

Examination

  • General: older man, mildly drowsy but rousable, appears unkempt; accompanied by daughter
  • Vitals: T 36.7 °C, HR 92 bpm, BP 132/80 mmHg, RR 16/min, SpO2 97% on room air
  • Mental status: inattentive, disoriented to date and place, impaired short-term memory, fluctuating alertness (worse at time of assessment)
  • HEENT: dry mucous membranes; pupils 4–5 mm bilaterally, reactive
  • Cardiovascular: normal S1/S2, no murmurs
  • Respiratory: clear breath sounds
  • Abdomen: non-tender, bowel sounds present
  • GU: palpable suprapubic fullness on light palpation
  • Neurological: no focal motor or sensory deficits; speech slightly slowed but coherent

Investigations

  • Medication review: amlodipine, atorvastatin, tamsulosin, oxybutynin started 4 days ago (anticholinergic); occasional diphenhydramine PRN (antihistamine with anticholinergic effects) (interpretation: increased anticholinergic burden)
  • CBC: WCC 7.8 x10^9/L (normal) (interpretation: no leukocytosis to suggest infection)
  • Serum electrolytes: Na 138 mmol/L, K 4.2 mmol/L, Cl 102 mmol/L (all within normal) (interpretation: no metabolic cause identified)
  • Creatinine: 90 µmol/L, eGFR ~65 mL/min/1.73m2 (baseline-ish renal function) (interpretation: renal function adequate)
  • Glucose (capillary): 6.3 mmol/L (interpretation: not hypoglycaemic)
  • CRP: 3 mg/L (normal) (interpretation: no acute inflammatory process)
  • Urinalysis (dip): trace leukocytes, no nitrites, specific gravity 1.020 (interpretation: non-diagnostic; no clear evidence of UTI)
  • Bladder scan post-void residual: 350 mL (interpretation: significant urinary retention likely due to anticholinergic effect)
  • ECG: sinus rhythm, rate 92 (no acute ischemia)
  • CT head: not performed initially (indicated only if focal neuro signs or head injury)

Diagnosis

  • Primary diagnosis: Medication-induced confusion/delirium due to anticholinergic toxicity

    • Evidence: acute onset over days with temporal relation to starting oxybutynin 4 days ago, features of delirium (inattention, fluctuating consciousness), signs of anticholinergic effects (dry mouth, constipation, urinary retention), normal routine labs and no fever.

  • Differential diagnoses:

    • Urinary tract infection causing delirium — less likely given afebrile state, normal WCC/CRP, non-diagnostic urinalysis
    • Metabolic encephalopathy (electrolyte disturbance, hypoglycaemia) — unlikely given normal electrolytes and glucose
    • Acute intracranial event (stroke, subdural) — less likely without focal neurological signs or history of significant head injury; consider if focal findings or persistent confusion
    • Underlying dementia with acute superimposed delirium — baseline cognition reportedly preserved; acute change favors delirium
    • Polypharmacy/opioid or benzodiazepine effects — patient not on chronic opioids/benzos but occasional diphenhydramine contributes to anticholinergic burden

Management

  • Immediate steps:
    • Stop oxybutynin immediately and advise cessation of diphenhydramine
    • Provide supportive care: reorientation measures, ensure hydration and nutrition, maintain a calm environment, involve family for reassurance
    • Address urinary retention: consider intermittent catheterization or indwelling catheter based on retention volume and bladder outlet obstruction assessment; consult urology if retention persists
    • Monitor vitals, fluid balance, and mental status frequently (e.g., delirium observation)
  • Medication review and reconciliation:
    • Review indication for anticholinergic therapy for BPH; consider alternatives (e.g., review need for antimuscarinic, consider mirabegron if appropriate or optimize alpha-blocker therapy)
    • Arrange pharmacist review for anticholinergic burden and deprescribing plan
  • Further investigations/consults if not improving:
    • If persistent confusion or new focal signs: perform CT head and neurology/geriatrics review
    • Geriatric medicine or inpatient liaison for delirium management and discharge planning
  • Symptom control:
    • Avoid benzodiazepines unless required for alcohol withdrawal
    • If severely agitated and risk to self/others, consider low-dose antipsychotic (e.g., haloperidol) after risk/benefit discussion
  • Disposition:
    • Likely admission for observation until delirium resolves and urinary retention managed; arrange follow-up and primary care communication about medication changes

Key Learning Points

  • Acute onset confusion in older adults is delirium until proven otherwise; always check recent medication changes as a reversible cause.

  • Anticholinergic medications (including oxybutynin and over-the-counter antihistamines) frequently precipitate delirium in older patients; perform medication reconciliation and reduce anticholinergic burden.

  • Investigations should aim to exclude common medical causes (infection, metabolic disturbance, urinary retention) while supportive care and removal of offending agents are immediate priorities.

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