A 75-year-old woman with advancing Alzheimer's dementia develops severe pneumonia. Her daughter says hospital antibiotic treatment is pointless and her mother would refuse it. How do the four principles interpret this case?

Autonomy: the decision should follow the patient's will, but dementia makes that will hard to know, and the daughter may not be a neutral surrogate. Non-maleficence and beneficence: treatment would save her life, but might only prolong suffering, unless she still lives a fairly contented life. Justice: does she have a claim to treatment, and are similar patients treated alike?

The question: is it ethically legitimate, or even required, to withhold the probably life-saving treatment of the pneumonia?

• Autonomy. Normally the decision follows the patient's will. With advanced dementia, the principle needs a case-specific reading: at what stage of dementia may others decide for her own good? Should the daughter decide as surrogate? Can we be sure she acts in her mother's best interest, and not out of an understandable self-interest in ending a burdensome period of care? Are there other reliable indications of the presumed will? Or should the doctors decide, based on clinical experience?
• Non-maleficence and beneficence. The duty of care normally requires a life-saving therapy. But with severe dementia, would antibiotics only prolong her suffering and so harm more than help? Then non-maleficence would argue for withholding. Or might she still lead a relatively contented life, in which case treatment benefits her?
• Justice. Does she have a claim, or even a right, to inpatient antibiotics under statutory insurance? Equal treatment of patients in similar situations, and alternative uses of the resources, could matter.

No principle yields the answer directly, but the interpretation isolates the two real questions: (1) how can we best respect her self-determination given advanced dementia? (2) will treatment benefit or harm her?

Go deeper:

• Wikipedia: Advance healthcare directive — the document that would have settled the "presumed will" question.