Advances in surgical techniques have reduced the need for blood transfusion and most anaemias can now be managed without transfusions. While the haemoglobin concentration assists the decision to transfuse a patient, there is no single threshold for transfusion. The need to give a blood component is also difficult to assess, but guidelines are available. Although Australian blood supplies have a high degree of safety, attention to details such as patient identification and compatibility will help to reduce adverse outcomes when a transfusion is indicated.
The transfusion of blood or its components (plasma, platelets, cryoprecipitate) has an important role in modern medicine and surgery. However, in recent years this role has been reassessed, especially in anaemia and in the perioperative setting. The majority of anaemias can now be treated without the transfusion of homologous blood, and careful risk assessment and the use of blood conservation techniques have made 'bloodless' surgery possible for most elective procedures.
Indications for blood transfusion
Blood transfusion is indicated to control the effects of a haematological deficiency, or to prevent problems, until the injury or disease process can be corrected or resolves. The focus should be on the patient's specific clinical problem, with transfusion viewed as an option only when alternatives have been considered and optimally used when possible.
Assessing acute blood loss and when to start transfusion remains controversial. However, it is reasonable to say that volume resuscitation does not need blood in the first instance. The decision to use blood should be made in the context of the patient's cardiocirculatory and respiratory status and haemoglobin level after resuscitation with clear fluid. If blood loss is accurately assessed a better prediction as to when red cell transfusion may be needed can be made.
Homologous blood transfusion should not necessarily be regarded as the first line of therapy for patients with haemopoietic defects, and in patients having elective surgery it is often possible to minimise or eliminate the need for transfusion. Clearly, if homologous blood can be avoided its potential hazards need not be considered. Making a decision to use blood components can be difficult and much debate continues in relation to the indications for their use.
Before giving patients blood or a blood component it is useful to ask a series of questions.
- What is the haematological defect?
- What is the most appropriate therapy for the patient?
- Are there alternatives to homologous transfusion?
- Is a blood component indicated and where should it be obtained from?
- What are the potential hazards of transfusion/component therapy?
- Can the risk of adverse effects be avoided or minimised?
- How should the treatment be administered and monitored?
- What is the time frame of the decision-making process?
- What is the cost of the haemotherapy?
- Is the patient fully informed of the medical decisions?
The clinician in the perioperative setting is confronted with the following decisions.
- Is this patient a potential 'bleeder', what is the haemostatic defect and what therapy is available to minimise bleeding?
- In patients without a pre-existing haemostatic defect, to what point can I haemodilute the patient before requiring transfusion of specific blood components?
- Are there autologous techniques appropriate for this patient (what, when and how)?
- Do I need to give homologous red cells?
- At what point does attention to haemostasis as well as oxygen transport become a consideration?
Evidence-based transfusion medicine and clinical guidelines
As with all modern medical therapy, transfusion and blood component therapy presupposes an understanding of the natural history of untreated and treated disease. In many disorders the clinical problem is well understood and there is good evidence for the benefits of transfusion or non-transfusion. Transfusion medicine, especially in the perioperative setting, therefore lends itself to the appropriate use of clinical guidelines (see Tables 1 and 2). If there is a reasonable probability of a patient requiring a red cell transfusion a sample of blood should be sent to the laboratory for 'type and screen'. Units of blood will only be released upon specific request by the clinician.
The clinician's responsibilities
The clinician requires a core knowledge of transfusion medicine focusing on the following:
- Has the clinical problem (e.g. anaemia) been correctly diagnosed and can it be corrected in the short or long term by specific therapy?
- Is there evidence that blood component therapy should improve the short-and long-term outcome for the patient?
- What alternatives are available?
- Have the specific clinical or laboratory criteria for transfusions been satisfied?
- Have the risks been assessed and balanced against the predicted benefits of blood component therapy?
- Has an appropriate blood component been selected?
- Who will administer and monitor the blood component?
- What end points will be measured to assess benefit?
- Is the patient appropriately informed about the risks and benefits of transfusion or no transfusion?
- Is the transfusion process being correctly documented and audited, from the decision to transfuse through to end points and complications?
Allain JP, Williamson LM. How can we best achieve optimal transfusion practice? Med J Aust 1997;167:462-3.
Farmer S, Webb D. Your body, your choice: the layman's complete guide to bloodless medicine and surgery. Singapore: Media Masters; 2000.
Australian Red Cross Blood Service. Transfusion medicine. Manual 2003. Blood transfusion practice and clinical use of blood in Australia. Melbourne: ARCBS; 2003.
http://www.transfuse.com.au/ResourceLibrary/Resource_Tmm.asp [cited 2005 Mar 14]
Professor Isbister is Chair of the Australian Red Cross Blood Service Advisory Council and a member of the Board.
In the box of examples of some of the products available for bowel preparation, Picoprep appeared to be listed as a magnesium preparation. Although it does contain magnesium oxide, it also contains sodium picosulfate and is therefore similar to Picolax which was listed as adiphenylmethane preparation.