A 72-year-old man on day 3 post-total hip replacement develops fluctuating confusion, disorientation at night (worse), visual hallucinations, and agitation. His family says he was cognitively intact before surgery. Which investigation is MOST important to order first?
- A Brain MRI with contrast
- B Blood glucose, electrolytes, renal function, urine analysis, O2 saturation ✓
- C Mini-Mental State Examination (MMSE) alone
- D EEG to rule out non-convulsive status epilepticus
Correct answer: B. Blood glucose, electrolytes, renal function, urine analysis, O2 saturation
Explanation
Post-operative delirium requires identifying reversible precipitants. The standard first-line workup includes metabolic panel (glucose, electrolytes, BUN/creatinine), oxygen saturation, urine analysis for infection, CBC, and review of medications (anticholinergics, opioids). MRI and EEG are reserved for focal neurology or seizure suspicion. MMSE documents severity but does not identify cause. Delirium is diagnosed clinically using tools such as the Confusion Assessment Method (CAM).
Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.