Advance Directives USMLE: Living Will, Proxy, POLST & DNR

An advance directive is a patient's own instruction, written or oral, for future care if they lose decision-making capacity: a living will records which treatments they want or refuse, and a durable power of attorney for health care (health care proxy) names the agent who decides for them. POLST forms and DNR or DNI orders are different: they are medical orders signed by a clinician, not advance directives. A directive guides care only when the patient lacks capacity and the situation it describes has arisen; a patient who has capacity always overrides it, and a DNR order means no CPR, not "do not treat." With no appointed agent or guardian, most states' laws name a default surrogate (typically a spouse or domestic partner, then adult children, parents and siblings), who decides by substituted judgment.

Living will vs health care proxy vs POLST vs DNR

What each one really does

• Living will. A limited document that goes into effect when the patient can no longer decide and a medical condition specified in it (typically a terminal condition, permanent unconsciousness or the end stage of a chronic disease) is diagnosed. State law often sets a process for confirming and documenting the incapacity and the condition, and the scope of living wills varies greatly by state.
• Durable power of attorney for health care. The patient (the principal) names an agent to make health care decisions, and only health care decisions, once the patient lacks capacity. The principal "can direct and override anything the agent does" while still capable.
• Oral directives count. The AMA Code describes advance directives, "whether oral or written," as tools for patients to express their values, goals and treatment preferences. Record what the patient tells you in the chart: a specific, consistent statement (for example, "no breathing machine if I can't recover") is strong evidence for the surrogate and the team; a vague remark is much weaker.
• POLST (Physician or Provider Orders for Life-Sustaining Treatment). It turns a seriously ill patient's current wishes into orders on CPR, the overall level of treatment (comfort-focused, limited or full) and often artificial nutrition. POLST and advance directives "support each other but do different things": POLST does not appoint a surrogate, and healthy people need an advance directive, not a POLST.
• Patient Self-Determination Act (1990). Hospitals and other facilities that receive Medicare or Medicaid funding must tell patients about their rights under state law to make treatment decisions and advance directives, and must document whether the patient has one.

Who decides when the patient cannot

Work down this list and stop at the first step that applies:

1. The patient, if capable now. "An advance directive never takes precedence over the contemporaneous wishes of a patient who has decision-making capacity" (AMA). Assess capacity first: can the patient communicate a choice, understand, appreciate and reason? See capacity vs competence.
2. The patient's prior wishes, in a living will or a clear oral directive, if they apply. The AMA tells physicians to "determine whether the patient's current clinical circumstances meet relevant thresholds set out in the directive."
3. The agent named in a durable power of attorney for health care (or a court-appointed guardian, where one exists), who follows the directive where it applies and otherwise uses substituted judgment.
4. A default surrogate under state law. Most states authorize one, usually in the order spouse or domestic partner, adult child, parent, sibling, then possibly other relatives or a close friend; the order and scope of authority vary by state. More on surrogate decision-making.
5. No one available. In an emergency, treat under the emergency exception to informed consent. Otherwise, ask the ethics committee to help determine the patient's best interest.

Surrogate standards. Substituted judgment comes first: what this patient would choose, based on their advance directive, recorded preferences, views about life and attitudes toward illness and suffering. Best interest applies only when the patient's wishes are unknown and cannot reasonably be inferred, weighing pain and suffering, the likely benefit, resulting impairments and quality of life as the patient experiences it.

Call the ethics committee (AMA) when no surrogate is available or there is disagreement about who it is, when a disagreement about treatment cannot be resolved, when an advance directive and the surrogate's wishes conflict, or when the surrogate's choice is clearly not what the patient would want, not in their best interest, or serves someone else's interests.

DNR and DNI: what they cover

• DNR = no CPR (chest compressions, defibrillation) if the heart stops. The AMA states that DNR orders "apply only to resuscitative interventions"; antibiotics, dialysis and symptom management are provided or withheld according to the patient's wishes.
• DNI is a separate order. A patient may decline intubation, CPR or both; read exactly what the order says.
• No order on the chart: at arrest, attempt resuscitation if it is medically appropriate.
• Before surgery or other procedures that risk arrest, confirm whether the patient wants the DNR to stay in effect, and follow those wishes.
• Out of hospital, EMS teams generally start resuscitation unless they are shown a valid DNR order or portable medical order such as a POLST.

How USMLE tests advance directives

Withdrawing a treatment that a directive or surrogate refuses is not assisted death; see physician-assisted death vs euthanasia for that line.

Practice question

A 68-year-old man with COPD is brought to the emergency department with 2 days of worsening dyspnea, fever and purulent sputum. Before this illness he lived independently and walked his dog daily; his COPD has never been considered terminal. A chest x-ray shows a right lower lobe infiltrate. After 2 hours of noninvasive ventilation, he is increasingly somnolent, cannot answer questions, and his arterial PCO2 is rising. Two years ago he signed a living will stating that if he has a terminal condition or is permanently unconscious, he does not want CPR or mechanical ventilation, and a durable power of attorney for health care naming his wife as his agent. The intensive care team expects him to recover with a few days of mechanical ventilation. His wife asks the team to intubate him: "He told me he would accept a breathing machine if it was temporary and he could get back home." His adult son, holding a copy of the living will, insists that his father "never wanted machines." Which of the following is the most appropriate next step?

A. Withhold intubation as directed by the living will B. Continue noninvasive ventilation until the family agrees C. Intubate the patient, as his wife requests D. Obtain an ethics consultation before deciding about intubation E. Petition the court to appoint a guardian

Answer: C. The living will is conditional: it covers a terminal condition or permanent unconsciousness, and a likely reversible, pneumonia-triggered exacerbation in a man whose COPD is not terminal is neither, so its refusal does not apply. The patient lacks capacity, so his appointed agent decides by substituted judgment, and her account of his wishes fits a time-limited course of ventilation for a reversible illness. Worsening mental status and rising PCO2 despite noninvasive ventilation are indications for intubation.

• A: applies a directive whose trigger has not been met.
• B: delays a needed intervention in worsening hypercapnic respiratory failure, and family consensus is not required when there is a legally appointed agent.
• D: an ethics consultation helps when a conflict persists, but it must not delay urgent care; here the agent's decision is consistent with the directive, and the son has no decision-making authority while the agent is available.
• E: he already has a legally authorized decision-maker; a court is slow and a last resort.

Once he recovers capacity, revisit his goals with him, update his directive, and consider a POLST if his illness progresses.

Key takeaways

• Living will = what the patient wants; health care proxy (durable power of attorney for health care) = who decides. Both are advance directives and apply only when the patient lacks capacity.
• POLST and DNR/DNI are medical orders, not advance directives; POLST is for seriously ill or frail patients and follows them across settings, including EMS calls.
• A capable patient's current decision overrides any directive, at any time.
• Check applicability: a living will limited to terminal illness or permanent unconsciousness does not cover a reversible illness.
• Agent first, then the state's default surrogate (usually spouse, adult children, parents, siblings; varies by state). Surrogates use substituted judgment, then best interest.
• DNR = no CPR only; antibiotics, dialysis, ICU care and symptom control continue as the patient wishes. Revisit the DNR before surgery.
• Oral directives count: document them. In an emergency with no known wishes and no surrogate, treat.

Sources

• Advance Directives — Merck Manual Professional Edition (2025)
• Do-Not-Resuscitate (DNR) Orders and Portable Medical Orders — Merck Manual Professional Edition (2025)
• Consent and Surrogate Decision Making — Merck Manual Professional Edition (2025)
• Opinion 5.2: Advance Directives — AMA Code of Medical Ethics
• Opinion 2.1.2: Decisions for Adult Patients Who Lack Capacity — AMA Code of Medical Ethics
• Opinion 5.4: Orders Not to Attempt Resuscitation (DNAR) — AMA Code of Medical Ethics
• About POLST — National POLST (2026)
• Treatment of Acute COPD Exacerbation — Merck Manual Professional Edition (2026)
• Advance Directives — StatPearls, NCBI Bookshelf (2025)
• Do Not Resuscitate — StatPearls, NCBI Bookshelf (2022)
• Advance care directives — MedlinePlus Medical Encyclopedia (2026)
• Evaluating Medical Decision-Making Capacity in Practice — American Family Physician (2018)