Considerable progress has been made in recent years in understanding the biochemical properties and clinical efficacy of hemoglobin substitutes. Cell-free bovine hemoglobin was approved for clinical use in South Africa in 2001, and active clinical trials using the same product are well underway internationally, including in the United States. This technology will likely prove to be a useful adjunct in treating anemia following major orthopaedic surgery. Blood requirements in orthopaedic surgery The impetus to develop hemoglobin substitutes stems from the fact that allogeneic blood transfusions are frequently required for surgical patients. Approximately two-thirds of all transfusions in the United States are related to surgical procedures [12]. The average hemoglobin drop is 3.85± 1.4 g/dl for single total knee replacement, 4.07±1.74 g/dl for total hip replacement, and 5.42±1.8 g/dl for bilateral knee replacement [13]. Bierbaum et al. prospectively evaluated 9,482 patients undergoing hip or knee arthroplasty and found that 30% received autologous blood and 16% received allogeneic blood during the post-operative period [3]. The risk factors associated with the need for allogeneic transfusion were a lack of autologous blood and a pre-operative hemoglobin below 13 g/dl. Of 8,561 patients whose pre-operative hemoglobin was known, 3,020 (35%) had a level of 13 g/dl or below. Of these 3,020 patients, 29% required allogeneic blood transfusion. It bears mention that the incidence of anemia is correlated with increasing age [2], so that older patients undergoing orthopaedic procedures are more likely to need allogeneic transfusions.
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