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Interact CardioVasc Thorac Surg 2008;7:759-763. doi:10.1510/icvts.2008.183582 © 2008 European Association of Cardio-Thoracic Surgery
The Haemonetics® Cell Saver 5 washing properties: effect of different washing pump and centrifuge speeds
a Department of Anesthesiology and Intensive Care, Regional Outpatient of Cardiology, Zalesskogo str. No 6, Novosibirsk 630047, Russia Received 10 May 2008; received in revised form 25 June 2008; accepted 27 June 2008
*Corresponding author. Tel.: +7-383-2281294; fax: +7-383-2262971.
This study evaluated the effect of different washing and centrifuge rates of the Cell Saver 5 on the quality of processed autologous blood. Autologous blood was washed with 1000 ml of sterile normal saline at centrifuge speed of 5650 revolutions per minute (rpm) (group I) or 4350 rpm (group II) with different washing pump speeds – 500, 800 and 1000 ml/min. Hemoglobin, free hemoglobin, hematocrit, erythrocytes, leukocytes, platelets, and protein were measured before and after processing. The highest values of hemoglobin, hematocrit and erythrocytes were achieved using 800 and 1000 ml/min pump speeds in group I and 500 ml/min speed in group II. Red blood cells concentration was higher in group I. There were no significant changes of free hemoglobin removal within group I. In group II the lowest free hemoglobin was achieved when 1000 ml/min rate was used. Platelets and protein did not depend on wash pump speeds in both groups. Platelet recovery in group I was higher than in group II at all washing pump speeds. Leukocytes were not adequately removed at all pump speeds. The Cell Saver 5 produces optimum results when the high wash pump speeds (800 and 1000 ml/min) and standard centrifuge speed are used.
Key Words: Blood; Cardiopulmonary bypass; Cell saver
Modern autotransfusion devices can provide different quality of processed autologous blood depending on operating modes [1]. Operation in automatic mode, which is usually recommended by the manufacturers, leads to a significant reduction of free hemoglobin, platelet concentration [2, 3], anticoagulants [4] and to excellent attenuation of some inflammatory markers in the final product [5]. However, automatic mode is not a unique mode. It has been found that different wash pump rates render essential influence on the quality of the processed autologous blood when using nominal (5650 revolutions per minute (rpm)) centrifuge speed of the Haemonetics® Cell Saver 5 (Latham bowl) (Haemonetics, Braintree, MA) [6]. We can suppose that the changes of centrifuge speed will also influence the composition of the final product. Different centrifuge speeds may also have impact on blood cells damage [7, 8]. In a similar device – The BRAT2 (Baylor bowl) (Cobe) – the centrifuge speed of 4400 rpm is used without any opportunity to regulate it, however, the manufacturer mentions that such a rate produces rapid separation of the red cells with minimal trauma. Cell Saver 5 has the opportunity to change the centrifuge speed during different stages of the working cycle. Thus, we performed the prospective randomized study to evaluate the effect of different washing modes and centrifuge rates of the Haemonetics® Cell Saver 5 on the quality of processed autologous blood.
The study design was accepted by the local Ethics Committee. After the cardiopulmonary bypass (CPB) termination the perfusate (residual CPB volume) was collected to the cardiotomy reservoir of the Cell Saver. Filling and emptying of the centrifuge bowl were performed in automatic mode. Washing parameters were changed. While processing the perfusate was washed with 1000 ml of sterile normal saline at a standard (5650 rpm – group I) or low (4350 rpm – group II) centrifuge speed in a random order. Washing pump speeds were also randomly changed – 500 ml/min, 800 ml/min or 1000 ml/min. Hemoglobin concentration (Hb), plasma free hemoglobin concentration (freeHb), hematocrit level (Ht), erythrocytes (Er), leukocytes (L) and platelets count (Tr), plasma protein (Pr) concentration were measured before and after processing with the use of Cell Saver: in the cardiotomy reservoir and in the reinfusion bag. Hb, Ht were measured using AVL OMNI 6 modular analyzer (Austria). FreeHb was measured using photometric method [9]. The delta (  ) was also calculated – the difference of determined parameters before and after washing for freeHb, Tr, Pr and the difference of parameters after and before washing for Hb, Ht, Er, L. The group means were compared using Wilcoxon matched pairs test (when values before and after processing were compared), Kruskal–Wallis ANOVA, Mann–Whitney U-test (when paired comparison between groups and multiple comparison within each group were performed) and expressed as mean±standard deviation (M±S.D.). When multiple comparison was performed – the level of significance of 0.017 was used (according to Bonferroni's correction).
Er count, Hb concentration and Ht level underwent the simultaneous changes during the washing cycle: their means considerably increased at all three pump speeds in group I and group II (P<0.01) (Tables 1 and 2). The Mann–Whitney U-test evaluated that the increase ( ) of Hb content, Er count and Ht level at the washing speed of 500 ml/min was significantly lower than at wash pump speeds of 800 and 1000 ml/min in group I (Fig. 1a–c). No significant difference between 800 and 1000 ml/min pump speeds was revealed. The results had proved to be opposite in the low centrifuge speed group. The increase of Hb concentration and Ht level at the washing speed of 500 ml/min was significantly higher than at other wash pump speeds. The increase of Er count in the final product at the washing speed of 500 ml/min was significantly higher than at the washing speed of 800 ml/min, but only the tendency between washing rates of 500 and 1000 ml/min was seen (P=0.110). No significant changes of Hb, Ht and Er were revealed between pump speeds of 800 and 1000 ml/min in group II. We also performed paired comparison between the same wash pump speeds of both groups using Mann–Whitney U-test. The Hb, Ht and Er increase () at wash pump speed of 500 ml/min did not differ between groups with different centrifuge speeds. The increase of these hematological values at pump speeds of 800 and 1000 ml/min was significantly higher in group I (P<0.001).
The freeHb concentration decreased after perfusate washing at all pump speeds in both groups (Tables 1 and 2). The freeHb concentration was found to be in the limits of normal values after processing in all groups and subgroups. No significant difference in freeHb removal between different wash pump speeds was determined in group I (Fig. 1d). However, the freeHb removal tended to increase at wash pump speeds of 800 ml/min (P=0.086) and 1000 ml/min (P=0.019) in comparison with 500 ml/min. The data obtained in the low centrifuge speed group are much clearer. The rate of freeHb removal at the washing speed of 1000 ml/min was significantly higher than at the speeds of 500 and 800 ml/min. No difference between 500 and 800 ml/min subgroups was found in group II. The paired comparison between groups did not reveal any difference of freeHb removal at wash pump speeds of 500 and 800 ml/min. The significant increase of freeHb removal at pump speed of 1000 ml/min was seen in group II in comparison with group I (P=0.000112). Tr count decreased at all pump speeds in both groups (Tables 1 and 2). No significant changes in Tr recovery were found in both groups at all washing pump speeds (Fig. 2a). The paired comparison revealed that the Tr recovery in group I was higher than in group II at all three washing pump speeds (P<0.001).
The Pr concentration decreased considerably at all pump speeds in both groups (Tables 1 and 2). No significant changes in Pr recovery were found in both groups at all washing speeds (Fig. 2b). The paired comparison revealed that the washing speeds of 500 and 1000 ml/min at the centrifuge speed of 5650 rpm were better Pr saving modes (P<0.017).
L count increased at all pump and centrifuge speeds (Tables 1 and 2). The Kruskal–Wallis analysis of variance did not reveal any influence of washing pump speed on
The performed study revealed that different centrifuge speeds and different washing rates provided different quality of the processed autologous blood. In group I the highest concentrations of Hb, levels of Ht and counts of Er were achieved when the high wash pump speeds were used (800 and 1000 ml/min). Such red blood cell concentrations are probably reached by the shortening time of the washing phase when high washing rates are used. It must be noted that the Ht levels were quite low at all wash pump speeds. The literature data demonstrate that the Ht of the final product after cell saver processing is 44.8–60% [1, 10, 11]. In our study the Hb concentration and Er count after processing in group I conform to the literature data. Low Ht levels can be explained in such a way. We used AVL OMNI 6 analyzer that utilized the conductivity based Ht measurement. It is known that the Pr, Na+, and Cl– are the variables having the most significant effect on the accuracy of conductivity based method [12] and exactly that variables (and also K+ and iCa++) demonstrate the diversity of changes after cell saver processing [13, 14]. That is why we, probably, obtained such low Ht levels in the final product. The best freeHb removal was reached by using the high wash pump speeds – 800 and 1000 ml/min. Probably, the high pumping speed of the saline to the bowl provides the maximal removal of the freeHb. Unfortunately, these data were not significant (800 ml/min vs. 500 ml/min, P=0.086; 1000 ml/min vs. 500 ml/min, P=0.019). So we can conclude that the use of standard centrifuge speed provides normal freeHb concentrations in the end product independently of the wash pump speed used. The most effective Tr salvage was reached at wash pump speed of 800 ml/min (however, the difference with 500 and 1000 ml/min was not significant: P=0.019; P=0.399). We can suppose that the main part of Tr pool is removed during the filling of the bowl due to the centrifugation, and then the Tr count changes are determined by the duration of the washing phase. Pr concentration did not depend on washing rates and decreased independently during the processing, perhaps due to the centrifugation. L were not adequately washed out at all pump speeds. The tendency to even higher L saving was seen at 1000 ml/min wash pump speed (P=0.034 vs. 500 ml/min). In group II the highest concentrations of Hb and levels of Ht were achieved when the low wash pump speed was used (500 ml/min). There was no significant difference in Er count between wash pump speeds of 500 and 1000 ml/min but the tendency was the same: the best concentration was obtained at wash pump rate of 500 ml/min in contrast with group I. Probably, low centrifuge speed worse packs the Er due to the low centrifuge force. This leads to more intensive Er removal from perfusate when high wash pump rates are used. The lowest freeHb concentration was achieved when the washing pump rate of 1000 ml/min was used. Thus, the high pumping speed of the saline to the bowl spinning with low speed provides the maximum removal of the freeHb. Tr count did not depend on wash pump speeds in this group. Probably, as in group I, the centrifugation during the filling cycle plays the key role in Tr removal while perfusate washing (even with low centrifuge speed) has no essential influence on it. Pr concentration did not depend on washing rates and decreased independently during the processing as in group I. The highest L removal was seen at the wash pump speed of 800 ml/min. However, the L concentration after washing and emptying the bowl was higher than before processing in both groups and at all wash pump speeds. So we can conclude that Cell Saver 5 does not adequately wash out the L and this conforms to literature data [15]. The findings of this study demonstrate that the use of standard centrifuge speed does not lead to greater mechanical damage of red blood cells than low centrifuge speed – it was confirmed by Hb, Er and freeHb measurements. Furthermore, the use of standard centrifuge speed provides higher red blood cell concentration and Tr salvage. However, the benefit of these activated Tr is controversial. The situation is rather conflicting when we use low centrifuge speed (4350 rpm) while washing the perfusate. The best freeHb removal is reached when using the wash pump speed of 1000 ml/min. However, when using this speed – the worse Hb concentration is seen. That is why the use of standard centrifuge speed (5650 rpm) is more suitable. Probably, the use of low centrifuge speed (4350 rpm) should not be recommended in routine clinical practice when operating Cell Saver 5. But if the operator for some reason (for example, to remove more Tr) uses the low centrifuge speed then to obtain the high quality final product (with high Hb, Ht, Er) he should use the low (500 ml/min) wash pump rate. However, if the goal of the operator is to perform the maximum possible removal of freeHb and L, he should use low centrifuge speed in combination with high (1000 ml/min) wash pump rate. Our data show that the Haemonetics Cell Saver 5 produces optimum results when the high wash pump speeds (800 and 1000 ml/min) and standard centrifuge speed are used. In such a case not only the perfect removal of freeHb but the maximum red blood cell concentration is seen.
The authors would like to thank Dr Elena A. Voloschuk for her helpful assistance in carrying out this study.
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Abstract
1. Introduction
