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Intraoperative Autotransfusion in Small Children

1999; Lippincott Williams & Wilkins; Volume: 88; Issue: 4 Linguagem: Inglês

10.1213/00000539-199904000-00015

1526-7598

Michael Booke, O. Hagemann, Hugo Van Aken, Michael Erren, J. Wüllenweber, HG Bone,

Trauma, Hemostasis, Coagulopathy, Resuscitation

Intraoperative autotransfusion (IAT) of washed red blood cells is an established method to reduce perioperative transfusion requirements [1]. However, this technique is not used in small children because it is technically impossible to wash and hemoconcentrate small volumes of salvaged blood. The processing of <300 mL of salvaged blood is considered a contraindication for IAT [2] because the smallest bowl available for autotransfusion devices has a capacity of 125 mL (Haemonetics Cell Saver 5 [HCS]; Haemonetics, Munich, Germany) and needs approximately 300 mL of salvaged blood to be completely filled. New technology of autotransfusion devices may improve blood salvaging in small children: smaller bowls (capacity 55 mL) are now available (DIDECO Compact-A & Advanced; Sorin Biomedica, Puchheim, Germany). A new generation of autotransfusion devices (CATS; Fresenius AG, Bad Homburg, Germany) based on the technology of cell separators is also available. The CATS has a washing chamber in the shape of a double spiral and processes shed blood continuously [3]. Since these new systems have become available, the limitations of conventional IAT should be examined in small children. Therefore, we performed an in vitro investigation in which we analyzed the efficacy of processing small blood volumes. Methods Using outdated, packed red blood cells (RBC) of an identical blood type, we analyzed the efficacy of different autotransfusion devices in an in vitro set-up. To better simulate clinical conditions, we diluted the RBC with lactated Ringer's solution to obtain a hematocrit of 30%. This blood solution was then processed by the autotransfusion devices. We choose the HCS with a centrifugation bowl (capacity 125 mL) as the conventional, established autotransfusion device and compared it with two new autotransfusion devices: the DIDECO with a small centrifugation bowl (capacity 55 mL) and the CATS. All autotransfusion devices were operated in their appropriate automatic mode. With each device, 100, 200, 300, and 400 mL of blood were each processed 10 times. Before and after the procedure, we measured the hematocrit (Hct), hemoglobin (Hb), and potassium concentration (K). Because outdated packed RBC were used, no coagulation factors were measured. To measure the efficacy of the autotransfusion devices in terms of RBC recovery and potassium elimination, we calculated the recovery rate and the elimination rate (Formulas 1 and 2, respectively). The recovery rate reflects the percentage of RBC recovered from the initial blood solution after being processed by the autotransfusion devices. The percentage of potassium washed out by the autotransfusion device was termed the elimination rate. Recovery rate, elimination rate, Hct, Hb, and K in the supernatant of the processed blood unit, as well as the time and saline required by the different devices, served as outcome measures. These variables should be predictable independent of the volume of blood being processed. Equation 1 and Equation 2 All data are presented as mean +/- SEM. A P < 5% was defined as significant. Significance was tested by the use of a factorial analysis of variance with post hoc Scheffe's F-test. Results The processing of different quantities of blood suspension with a predefined Hct by different autotransfusion devices yielded blood products of significantly different quality (Figure 1). The HCS delivered a Hct as low as 25% +/- 1% when 100 mL was to be processed, but a Hct of 48% +/- 1% when 200 mL was to be processed. Processing 300 mL of blood caused a decrease in Hct to 34% +/- 2%, whereas the Hct increased again when 400 mL of blood was to be processed (47% +/- 1%). The DIDECO and CATS consistently produced a Hct >50% and 60%, respectively. Despite these differences in Hct, the recovery rate of RBC was near 100% with the CATS and the HCS, whereas it was significantly lower with the DIDECO when only 100 or 200 mL of blood was to be processed (80.8% +/- 2.8% or 85.4% +/- 2,1%) (Figure 1). The elimination rate for potassium was comparable for all devices at all blood volumes processed (Table 1). The time and saline required for processing the blood solutions differed among the tested devices: the CATS was the fastest and most efficient. When higher blood volumes were to be processed, the DIDECO required significantly more time than the other devices.Figure 1: Hematocrit and red blood cell recovery rate obtained from small volumes of blood with a given hematocrit of 30% after being processed with three different autotransfusion devices. HCS = Haemonetics Cell Saver 5, Haemonetics, Munich, Germany; DIDECO = DIDECO Compact-A & Advanced, Sorin Biomedica, Puchheim, Germany; CATS = Fresenius Continuous Autotransfusion System, Bad Homburg, Germany, RBC = red blood cells. *P < 0.05 versus HCS. [dagger]P < 0.05 versus CATS.Table 1: Data for Three Autotransfusion DevicesDiscussion Due to limited technology, anesthesiologists who want to use IAT in small children may be forced to develop their own methods. Michaelis et al. [2] added hydroxyethyl starch to shed blood after it was processed with a conventional autotransfusion device (225-mL bowl). They then allowed the RBC to settle while the starch remained in the supernatant. They then retransfused the RBC that had settled to the bottom of the retransfusion bag. However, this technique may not be recommended for widespread clinical use because the quality of the retransfused blood (Hct, Hb, K, etc.) is difficult to predict. We found that Hct is unpredictable and too low if blood volumes 60% of the processed blood independent of the amount of shed blood to be processed. Further, the CATS produces a recovery rate near 100%, whereas the DIDECO only recovers 81%-88% of the RBC (Figure 1). Consequently, the blood unit derived from the DIDECO contains less RBC than that derived from CATS. Given the predictable Hct at any blood volume processed, the consistently high recovery rate of nearly 100%, and the efficiency concerning the time and saline required for processing shed blood, the CATS seems to be the preferable device for IAT in pediatric surgery. In summary, recent technology may allow the use of IAT in pediatric surgery. The ASA Task Force on Blood Component Therapy has recommended using IAT whenever reasonable [4]. This study suggests the feasability of IAT in small children. The clinical use of these newer devices for IAT should be further examined.