Post-operative confusion in an older man with depression
A 68-year-old retired teacher is assessed on day 2 after elective right total hip replacement under spinal anaesthesia. He has type 2 diabetes, hypertension and recurrent depressive disorder, for which he takes sertraline 100 mg daily and zopiclone 7.5 mg at night. Post-operatively he is on morphine patient-controlled analgesia (18 mg in the last 12 hours), regular diphenhydramine 25 mg three times daily for itching, promethazine 25 mg for nausea, oxybutynin 5 mg twice daily because of catheter-related bladder discomfort, and hyoscine butylbromide. Overnight the nurses report that he is pulling at his cannula, seeing insects on the ceiling, and is difficult to rouse. On review his attention wanders, he is oriented to person only, and the CAM is positive. Temperature 36.9°C, SpO2 94% on air, pulse 104, BP 142/78. Haemoglobin is 9.8 g/dL (pre-operative 12.4), sodium 132 mmol/L, creatinine 130 µmol/L (baseline 88), and urine dipstick is positive for leucocytes and nitrites.
1. Formulate the case: what is the most likely diagnosis, and how would you rank the contributing factors? How would you distinguish this from a depressive relapse, an emerging dementia and serotonin toxicity?
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The syndrome is hyperactive–mixed delirium: acute onset, fluctuating course, inattention (CAM positive), disorientation and formed visual hallucinations. Ranked contributors: (1) cumulative anticholinergic burden - diphenhydramine, promethazine, oxybutynin and hyoscine all cross the blood–brain barrier and are additive in an older brain; (2) post-operative anaemia (Hb fell 2.6 g/dL) with possible hypoperfusion and mild hypoxia (SpO2 94%); (3) opioid load and uncontrolled pain; (4) acute kidney injury (130 vs 88 µmol/L), which reduces clearance of renally excreted drugs and metabolites; (5) probable urinary tract infection; (6) hyponatraemia 132 mmol/L - consider SSRI-associated SIADH; (7) sleep deprivation, unfamiliar ward, possible sensory impairment.
A depressive relapse would show stable rather than fluctuating cognition, diurnal mood variation and psychomotor change, not formed visual hallucinations. Dementia can coexist, but an abrupt 48-hour decline with fluctuation points to delirium; screen cognition properly after recovery. Serotonin toxicity is unlikely: there is no clonus, hyperreflexia, tremor, diarrhoea or hyperthermia, and sertraline is his only serotonergic drug - but keep looking for another cause rather than anchoring.
2. Outline your immediate non-pharmacological and pharmacological management, including which drug you would choose, its dose and monitoring. What would you avoid?
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First, stop all four anticholinergic/antihistamine agents - diphenhydramine, promethazine, oxybutynin and hyoscine. This is often the single most effective intervention and is easily missed because they are prescribed as 'routine'.
Non-drug measures: reorientation, glasses and hearing aids, daylight exposure and sleep hygiene, family presence, early mobilisation, avoid unnecessary catheterisation and physical restraint, treat pain, correct hypoxia, treat the UTI according to culture, and give cautious fluids for pre-renal AKI. Transfuse if anaemia is symptomatic or compromising oxygen delivery, and check an ECG.
Drug treatment is reserved for severe distress or danger to self/others. Haloperidol 0.5 mg orally (or 0.25–0.5 mg IM), repeated no more often than every 2–4 hours, at the lowest effective dose, with ECG monitoring of QTc. Quetiapine 12.5–25 mg is an alternative but is more sedating and hypotensive. Avoid benzodiazepines unless there is withdrawal or severe anxiety, because they worsen confusion and falls; avoid zopiclone as a ward sleep aid; avoid antipsychotics altogether if Parkinsonism is present. Monitor sedation, QTc, falls, fluid balance and mental state at least twice daily.
3. What medication changes and discharge plan would reduce the risk of recurrence? Address the sertraline, zopiclone, hyponatraemia and future anaesthetics.
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Sertraline: continue it - abrupt withdrawal risks discontinuation syndrome and depressive relapse, and it is not the main culprit. However, check serum sodium and urine osmolality; if SIADH is confirmed and persistent, switch to an agent less associated with hyponatraemia (for example mirtazapine) and monitor sodium after any change.
Zopiclone: review rather than reflexively continue. If he has been taking it nightly for years, taper to avoid rebound insomnia and withdrawal; replace with sleep hygiene and behavioural measures. Do not use it to treat delirium.
Prevention: flag 'anticholinergic - avoid in elderly' prominently in the chart, give the patient a card, and inform the surgeon and anaesthetist. Request a pre-operative cognitive screen and medication review (anticholinergic burden scale) before any future anaesthetic, and avoid diphenhydramine and promethazine in older adults.
Discharge: delirium often takes weeks to resolve. Arrange a repeat cognitive assessment (MMSE/MoCA and functional history) at 6–8 weeks to distinguish resolving delirium from underlying dementia, a falls assessment, GP and community psychiatric nurse follow-up, a written medication list with rationale, and driving advice until cognition has recovered.