Commentary: practicalities of seeking consent and gaining understanding

BMJ 2010; 341 doi: (Published 24 August 2010) Cite this as: BMJ 2010;341:c4000
  1. Ravi Gill, consultant anaesthetist
  1. 1Shackleton Department of Anaesthesia, Southampton University Hospital NHS Trust, Southampton SO16 6YD
  1. ravi.gill{at}

    Farrell and Brazier set out the arguments for obtaining specific informed consent for allogeneic blood transfusion.1 They do not deal with allogeneic blood products, but I think their article can be assumed to cover this too. This subject is controversial, and the question of how to seek and record consent has been the subject of a recent consultation by the Department of Health’s Advisory Committee on the Safety of Blood, Tissues and Organs. A question Farrell and Brazier avoid is who should be responsible for gaining informed consent? Should it be those who provide the blood (the transfusion service, probably most informed about the risks) or those who prescribe it (probably least informed)? This is of crucial importance in the debate and has considerable resource implications.

    The table of adverse events in Farrell and Brazier’s paper, taken in isolation from the Serious Hazards Of Transfusion 2008 report, might make worrying reading. But what is the denominator? There were 5367 reported serious adverse events in 12 years from 28 887 455 issues of blood and blood products from the National Blood Service—an incidence of 0.019%.2 This calculation does not accurately describe risk but shows that the blood supply and its management is generally safe.

    Are the risks of transfusion high enough to warrant specific informed consent? Let us look at an example from the area in which I work—elective coronary artery bypass grafting (CABG). The accepted national mortality for this procedure is 0.5-2%. In simple understandable language you could tell a patient that, at worst, two in every 100 elective patients might die.

    Secondly, the chance of receiving a blood transfusion during elective CABG is about 30%; there are no good national data at present, and transfusion practice varies widely from centre to centre. Given that 0.019% of all blood issues from the UK National Blood Service from 1996-2008 were associated with a reported adverse event, the risk to elective CABG patients is vanishingly small.

    In my opinion patients should be informed of the risks of a procedure, the chances of receiving blood during that procedure, and what measures might be used to avoid unnecessary transfusion, but is this such a large risk that specific separate consent is required for the blood transfusion? A patient signing a standard NHS consent form will be giving their consent to a blood transfusion if required. I would hope that this was an informed choice and that the clinician as well as mentioning the possibility of a blood transfusion also mentions that transfusion itself has some risks, albeit small.

    What is missing in the debate surrounding informed consent is the true nature of patient understanding, what information patients want to know, and how to deal with patients who wish to know only the minimum. There is little work in the area of assessing the understanding of the information given to patients. Clinicians often find it difficult to be certain how much patients or their relatives have correctly understood the information given to them. Understanding is affected by who is giving them the information, how it is explained, and the time or environment required to assimilate information. A paternalistic approach is unacceptable in medical practice; a common sense approach—explaining things clearly, tailoring what is said to what the patient seems to want, and checking understanding—is required for good medical practice.


    Cite this as: BMJ 2010;341:c4000


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