title: [Transfusion of recuperated blood in total knee arthroplasty].
abstract: OBJECTIVE
  Autologous blood transfusion is not a routine procedure in knee replacement surgery. Several authors have proposed recovering blood shed during the procedure to limit the need for homologous transfusions. The purpose of this retrospective study was to analyze the amount of blood recovered and reinfused with a blood conservation system (MI, USA) and its effect on hemoglobin level five days after surgery in 405 consecutive patients undergoing total knee arthroplasty.
  
  
  METHODS
  Preoperative intravascular blood volume and hemoglobin level were used to calculate the quantity of hemoglobin transfused expressed in g/dl at time t 0 of transfusion then at day 1 and day 5 postop. Autologous blood transfusion was not programmed for any of these patients. Twenty patients were given homologous blood transfusions and were excluded from the analysis of data on recovered shed blood but were included in the analysis of risk of homologous transfusion. The analysis thus included 385 patients who did not require homologous blood transfusion. Shed blood was reinfused in 337 patients; no transfusion was performed for 48 patients whose drainage produced an insufficient volume. The same analysis was performed for three sub-groups of patients: 205 patients whose transfusion volume was less than 10% of their intravascular volume, 132 patients whose transfusion volume was greater than 10% of their intravascular volume, and 50 transfused patients who weighed less than 70 kg.
  
  
  RESULTS
  Mean transfusion volume was 516 ml (range 100-1440 ml), accounting for 59% of the drainage volume over 24 hours and 32% of total estimated blood loss. On the average, the whole blood shed and reinfused contained 60.60 g hemoglobin and increased serum hemoglobin by 0.97 g/dl at day 5 postop (with a wide range: 0.18-2.74 g/dl). Mean transfusion volume, based on hemoglobin equivalent packed cell units, corresponding to 10% of the mean intravascular volume was taken as the threshold of transfusion efficacy. Among the 132 patients whose transfusion volume was greater than 10% of the intra-vascular volume, hemoglobin level at day 5 postop increased 1.32 g/dl on the average. Among the 205 patients whose transfusion volume was less than 10% of the intravascular volume, hemoglobin level on day 5 postop increased 0.74 g/dl on the average. In patients weighing less than 70 kg, transfusion increased hemoglobin level on day 5 postop 1.23 g/dl on the average. The probability of transfusion of more than 10% of the intravascular volume was 0.66 +/- 0.1 in patients weighing less than 70 kg and 0.33 +/- 0.05 for the entire population (p<0.001). The fall in mean hemoglobin level from day 0 to day 5 was 3.46 g/dl in transfused patients and 4.16 g/dl in non-transfused patients (p<0.0001). Reinfusion of shed blood allowed 80 more patients (20% of the 405 patients in this series) to maintain their hemoglobin level above 9 g/dl on day 5 postop. The probability of homologous blood transfusion for serum hemoglobin<8 g/dl was 0.5 +/- 0.08. Applying this probability in a situation without recovery of shed blood, the total number of homologous blood transfusions would have increased from 4.9% to 10.7% (p<0.01).
  
  
  CONCLUSIONS
  Patient follow-up confirmed the absence of specific problems. Mean transfusion volume was 516 ml with a 59% (mean) reinfusion/drainage ratio, in line with data reported in the literature. The efficacy of the blood conservation system was unpredictable due to the wide range of blood volume transfused, and consequently of hemoglobin transfused, related to wide interindividual variability for total blood loss and drainage volume. Since the mean volume of reinfused blood contained the same quantity of hemoglobin as one packed red cell units, it would appear reasonable to take 10% of theoretical intravascular volume as a threshold above which the transfusion method becomes efficacious.
  
  
  CONCLUSIONS
  Considerable interindividual variability in total blood loss and total drainage volume compromises the overall efficacy of blood conservation systems. Increase in hemoglobin level on day 5 postop was vary variable in this series of reinfused knee arthroplasty patients (range 0.18 - 2.74 g/dl) with a mean of 0.97 g/dl which corresponds to one packed red cell unit. The probability that the transfused volume would be greater than 10% of the theoretical intravascular volume was 0.66 +/- 0.1 in patients weighing less than 70 kg versus 0.33 +/- 0.05 for the entire population (p<0.001). This finding would suggest that a blood conservation system should be used routinely in patients weighing less than 70 kg. Conversely, the use of the system as a routine measure for all knee arthroplasty patients with the aim of limiting the risk of homologous blood transfusion to a minimum would divide the risk by two and also avoid the risk of viral contamination and identification errors.
authors.affiliation: Chirurgie Orthopédique et Traumatologique, Centre Hospitalier de Denain, Clinique Villars, 59220 Denain.
authors.forename: E
authors.initials: E
authors.lastname: Pitsaer
mesh_terms: D000368:Aged; D000740:Anemia / Q000097:blood / Q000209:etiology / Q000628:therapy; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects; D016063:Blood Loss, Surgical / Q000706:statistics & numerical data*; D001800:Blood Specimen Collection / Q000295:instrumentation / Q000379:methods; D001804:Blood Transfusion, Autologous / Q000295:instrumentation / Q000379:methods*; D001810:Blood Volume; D004322:Drainage / Q000295:instrumentation / Q000706:statistics & numerical data*; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D011300:Preoperative Care / Q000379:methods; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors
chemical_list: D006454:Hemoglobins