Definitions and Distinctions

Voluntary consent

Consent must be given freely without pressure or undue influence. Pressure may come from other family members, partners or other carers and doctors must be aware of this. Competent adults may refuse a treatment in its entirety, though may not compel a doctor to perform part of a treatment if by refusing specific components of a treatment, the doctor feels the treatment as a whole now presents an increased risk to the patient. Consent may be implied by the conduct of the patient during interactions with the health care professional (holding an arm out for venepuncture). While this may prevent a claim of trespass against the health care professional, it does not demonstrate that the patient has had the material risks of the procedure explained to them and that they have understood. Where a procedure carries a material risk, informed consent must be obtained. Recent case law has also raised the importance of the timing the consent process; the patient must have an appropriate time to consider the information given to them and make a decision. Taking consent on the day of surgery may be construed as placing undue duress on a patient and may make the consent obtained open to legal challenge.

Informed consent

A patient must understand the nature, purpose and potential complications of any procedure to be considered informed. They should be aware of all the alternatives available to them including not having the procedure performed and the consequences of inaction. The amount and nature of information disclosed to the patient must be tailored to the individual and address what this patient would regard as relevant. Commonly occurring side effects should be discussed. Rare risks should be discussed where it is felt that the potential for such an event (no matter how rare) would change the patient’s decision to proceed; this is of particular importance where a complication may be of special significance to the individual (vocal cord damage to a professional singer). A recent legal decision has emphasized this stating that clinicians should take “reasonable care to ensure that the patient is aware of any material risks involved in any recommended treatment and of any reasonable alternative or variant treatment”. Furthermore, not only must the nature and material risks of the procedure be explored but the operators and their relative experience should also form part of the consent discussion. The late change of operating staff may also leave the consent process open to legal challenge.

Competence and capacity

A competent adult is a person who has reached 18 years of age (16 in Scotland) and who has the capacity to make decisions on their own behalf regarding treatment. A person demonstrates capacity if they are able to:

  1. Understand the information relating to the decision they are about to make.
  2. Retain that information.
  3. Use or weigh that information as part of the process of making that decision
  4. Communicate that decision to others.

No other person may consent to treatment on behalf of a competent adult and an apparently unreasonable decision by a patient does not necessarily imply that a patient lacks competence. A patient’s ability to comprehend and make a balanced choice may be affected by factors such as shock, fatigue, pain or medication, however their presence does not preclude the patient retaining the capacity to self determine and in some cases patients may have capacity to consent to some interventions but not to others.

Refusal and withdrawal of consent

If a competent patient makes a voluntary and informed decision to refuse a treatment, this must be respected, except in circumstances defined by the Mental Health Act (1983), even of this results in the death of the patient or an unborn child. A competent patient is entitled to withdraw consent at any time, including during the performance of a procedure. A patient may on occasion wish to withhold consent for part of a procedure or technique (e.g. wishes general anaesthesia, but not cannulation awake or anaesthesia but not awake fibre optic intubation). Where selective refusal occurs, a practitioner is not required to offer the procedure as a whole if refusal of part of it (i.e. the the awake fibre optic intubation) renders the overall technique unsafe. If a patient does object during a procedure, the treatment must be stopped immediately and the reasons for the patient’s decision established as well as the consequences of failing to complete the procedure explained. If the sudden abandonment of the procedure places the patient’s life in immediate danger, then it should be continued and stopped at the earliest point when this risk has passed.


Patients who have deliberately harmed themselves may present complex difficulties in their treatment, particularly if they are refusing assistance. Where a patient has attempted suicide and/or rendered themselves unconscious, emergency treatment should be given if there exists any doubt regarding their intentions or capacity at the time of the injury. If a patient is able to communicate, then they should have an assessment of their mental capacity and if deemed to be not competent treated on a basis of temporary incapacity. If a competent patient has deliberately harmed themselves and is refusing treatment, a psychiatric opinion should be sought. If the use of the Mental Health Act (1983) is not appropriate, then their refusal must be respected, although attempts should be made to encourage them to seek help.
Here are some useful links looking at consent:

  1. General Medical Council (GMC) – consent to treatment
  2. GMC – 10 questions on consent
  3. GMC – consent resources
  4. HM Government – reference guide for consent for examination or treatment
  5. Association of Anaesthetists of Great Britain and Ireland (AAGBI) – consent for anaesthesia*
  6. British Medical Association (BMA) – consent guidance
  7. AAGBI – guidance on anaesthesia for Jehovah’s Witnesses

Here are some up to date explanations of the latest developments and controversies in consent law:

  1. Hailsham Chambers (2015) – The Montgomery decision and its effect on consent
  2. – The Jones decision and its effect on patient choice and late changes
  3. McCombe K, Bogod D. Paternalism and Consent: Has the law finally caught up with the profession? Anaesth 2015;70:1016–1019

Here are some useful podcasts looking at case studies involving complex consent issues:

  1. Inside the Ethics Committee, BBC Radio 4 – Needlesticks and HIV testing (ITEC)
  2. Inside the Ethics Committee, BBC Radio 4 – Learning difficulties and consent


*This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. Please cite all material as: ‘Source: AAGBI: Consent for anaesthesia 2017: Association of Anaesthetists of Great Britain and Ireland. Yentis SM, Hartle AJ, Barker IR, et al. Anaesthesia 2017; 72: 93-105.

This website uses Cookies, for further information see our privacy policy.