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excluded from the evaluation. Of the 52 cases in which the hematocrit target value was not reached, the emergency option was used in 6 % of cases, whereas a strong dilution effect was identified in 87 %( due to one of the reasons already mentioned can be assumed). This means that only in 7 % of cases, neither the emergency option nor a dilution effect was likely to be the cause of the deviation from the hematocrit target value. In the remaining cases, the hematocrit in the autotransfusion blood was always 45 %. Nevertheless, autotransfusion blood with a hematocrit 50 % was re-transfused, particularly for ethical reasons, if the total red blood cell collection volume was low. Therefore, the hematocrit of the autotransfusion blood can be actively influenced by the anesthesiologist responsible for cell salvage, who may accept deviations at their discretion. Of the 11 cases out of 130 in which the total protein elimination of over 90 % was not achieved, 6 cases showed minimal deviations from the target value, with a total protein elimination of over 88 %, which could be within the measurement tolerance. In the remaining 5 cases, the emergency option was used in one case, and one had a strong dilution effect. This leaves 3 cases with a total protein elimination below 88 % without the reasons already listed. Unlike the hematocrit, the total protein elimination was not determined directly by the cell saver, but only in the laboratory. Therefore, possible sources of error in these cases included sample collection, transport, and laboratory analysis, all of which increased the likelihood of errors in the process of determining laboratory data.
The optimized program( Popt) of the Sorin LivaNova Xtra Ò cell saver is usually used in our hospital. According to the manufacturer, this achieves a hematocrit in the autotransfusion blood of 60 – 65 % and a total protein elimination of over 95 % with a wash cycle duration of 5 min [ 18 ]. However, the emergency option can be activated for operations with particularly heavy blood loss. This means that the blood is processed within approximately 3 min, although this results in a lower hematocrit of around 50 % in the autotransfusion blood and a total protein eliminationofover92 % accordingtothemanufacturer’ sspecifications [ 18 ]. The hematocrit indicated by the sensor of the cell saver Sorin LivaNova Xtra Ò was compared with the hematocrit values determined by the HemoCue Ò Whole Blood Haemoglobin System Analyser in a study published by Yarham et al. in 2011. The cell saver Sorin LivaNova Xtra Ò showed an average hematocrit error of + 4 % [ 19 ]. However, in a further study published the following year, Overdevest et al. [ 20 ] concluded that the hematocrit sensor of the Sorin LivaNova Xtra Ò underestimated the hematocrit in the processed blood by approximately 15 % compared to the laboratory device CELL-DYN Sapphire Ò. The hematocrit sensor of the Sorin LivaNova Xtra Ò was previously used in a study by Melchior et al. [ 14 ] for the sole determination of the hematocrit. Several studies have shown that the hemoglobin or hematocrit value of patients increased postoperatively after the intraoperative use of cell salvage, even if the autotransfusion blood itself did not reach the target value of a hematocrit above 50 % on average [ 16, 17, 21 ]. In addition, the hemoglobin or hematocrit value of the patients who underwent intraoperative cell salvage increased even more postoperatively than in those who received a homologous red blood cell concentrate [ 17 ]. The absolute quantity of red blood cells is more important than maintaining the target value hematocrit [ 22 ], along with red blood cell yield and, if possible, an increase in the collection volume [ 21 ]. Accordingly, it can be concluded that compliance with the hematocrit target value of the autotransfusion blood is not mandatory for the success of the therapy. In addition, deviations in hematocrit can be accepted and actively influenced by the physician in certain clinical situations. Studies addressing the impact of retransfusing cell salvaged blood with less than 90 % of total protein elimination are missing.
Limitation
The present study is a retrospective data analysis. The number of cases and the patient collective were determined by everyday clinical practice. The hematocrit values that were extracted directly from the cell saver are less accurate than the value that were determined by a laboratory device. In addition, the evaluation of total protein elimination was based on a small sample size.
Conclusion
In the retrospective data analysis presented showed that the target values for total protein elimination and hematocrit in autotransfusion blood were largely achieved during intraoperative use at the Charité Mitte campus and the Benjamin Franklin campus. The determination of total protein elimination with a target value of > 90 % should remain an integral part of quality control for cell salvage applications, as it is best suited for evaluating the function and suitability of the tested cell saver. However, the quality control requirement for the hematocrit to be above 50 % should be reconsidered and could be changed from a mandatory quality assurance value to an optional measurement. The implementation of quality assurance parameters in the intraoperative use of cell salvage varies and only few countries define target values as quality criteria. Therefore, harmonization by international expert committees in anesthesia should be discussed.
Funding This research did not receive any specific funding.
Conflicts of interest Authors declared no conflict of interest.
Data availability statement
Questions regarding data sharing should be addressed to the corresponding author.
Author contribution statement
DD analyzed the data, interpreted the data, and wrote the manuscript. EK, KP, and PW collected the data and interpreted the data. KE interpreted the data. FH edited the manuscript. AP interpreted the data and edited the manuscript. All authors discussed, commented on, and approved the manuscript in its final form.