Massive Blood Replacement

Since, depending on the circumstances in which it occurs, massive blood loss is associated with different clinical effects and since opinions differ as to how the associated complications should be dealt with or prevented, we invited specialists in several different disciplines and with various areas of clinical expertise to answer the following questions: (1) How would your define a massive transfusion in your area of clinical practice? (2) What is your choice of fluid replacement? (3) What measures do your take to ensure rapid transfusion? (4) What are your indications for the transfusion of platelet concentrates? (5) When do you ask for supplementary clotting factors: do you have a ‘formula’ or are you guided by measurements, made either in the laboratory or in the operating theatre, e.g. using the thromboelastograph? (6) Are there any other measures which you consider to be important in dealing with a massive haemorrhage? Many of the contributors consider that the basic definition of massive blood loss – one blood volume in a few hours – is inadequate because, in some cases, much larger volumes may be lost in a much shorter time. Dr. Hiippala is the only one who defines massive haemorrhage in ‘functional’ terms, i.e. taking factors other than just the extent of blood loss into account. This approach is interesting since it takes into consideration the circumstances in which haemorrhage takes place. For example, in the injured patient, hypovolaemia and hypothermia due to exposure following trauma may impair platelet function, leading to further haemorrhage. All the contributors use red cells supplemented with crystalloid or colloid solutions, although Dr. Weiskopf points out that whole blood would be an asset in massive transfusions. Those who mentioned colloids were quick to exclude dextran and some starch preparations because of their effect on coagulation. Only Drs. Boyce and Higgs use albumin routinely for volume replacement. It has been demonstrated, in a series of studies from Seattle [1, 2], that in haemorrhage requiring the transfusion of some 20 units of blood a tendency to bleed abnormally occurs at platelet counts of 50 E109/l or l ss. It is difficult to translate this information into safe clinical practice because it takes some time to count platelets and more to obtain a supply of them, and to wait until the count falls to 50E109/l before seeking supplies seems to be delaying action too long for almost all of our contributors. Most prefer to start thinking, at least, about replacement therapy when the platelet count is 100 E109/l and transfusion needs to be continued. The Seattle workers referred to in the previous paragraph concluded that fresh-frozen plasma (FFP) was seldom necessary [1] in the patients they studied who received large transfusions. It has since been suggested that the ‘modified whole blood’ which they used may have contained some clotting factors and that the results of their study would have been different if they had used red cell concentrates and saline for volume replacement, as is more commonly done. A laboratory study of coagulation tests [3] in patients who received large transfusions of this combination (red cells and saline) showed abnormalities of coagulation after 12 units of red cells had been transfused, and marked abnormalities after 20 units. Two small clinical studies of blood loss [4, 5] of about one blood volume in surgical patients, while confirming these findings, showed that by no means all the patients showed a tendency to bleed abnormally. It has therefore been recommended that FFP should be administered if there is evidence of coagulopathy in the presence of a blood loss equal to the patient’s blood volume, with the expected abnormalities in clotting tests [6]. Although our contributors were in general agreement with this advice, there were some exceptions. Prof. Kretschmer prefers to give FFP according to a formula as soon as 20% of the blood volume has been lost. Dr. Hiippala, although happy to defer FFP administration until a full blood volume has been replaced, argues for very generous use of FFP thereafter. Drs. Higgs and Royston take a different approach, preferring to rely on some form of thromboelastograph (TEG) rather than on laboratory tests to indicate the need for platelets and clotting factors. Dr. Royston points out that platelet function, as well as number, is important in haemostasis, a fact with particular relevance to cardiac surgery. Dr. Hiippala regards the TEG as too slow to be helpful and Dr. Weiskopf’s view is that the instrument has not been sufficiently validated to be relied on in clinical practice. In considering other important measures, almost all our contributors stressed the importance of keeping patients and intravenous fluids warm when treating massive haemorrhage. The use of cryoprecipitate when appropriate was also mentioned. Two of our contributors put the case for the use of specific measures to limit blood loss, viz surgery