Please see Bibliography of References for a list of abstracts, manuscripts and posters.
Jeger V, Fontana S, Baur N, Luginbuhl M, Ferretti A, Zimmermann H, Exadaktylos A. Int Care Med. 2008;34(Supp 1):S94. Abstract 0356.
Introduction: In the past, non-invasive tissue oxygenation (StO2) measurement by near infrared spectroscopy (NIRS) and iatrogenic ischemic stress test (IIST) has been used to detect under-perfusion in shock patients, mainly in ICU. IIST has not been performed in a prospective controlled setting with a standardized blood loss. Therefore to investigate if blood loss of 500ml is leading in healthy blood donors to detectable changes by NIRS.
Methods: Prospective evaluation of 20 healthy female blood donors (500ml, ca.10% of circulating blood volume) with a body weight between 50 and 65kg. StO2 was continuously measured on the thenar eminence with InSpectra® (Model 650, Hutchinson Technology, Minn.USA). From the StO2 values and the tissue hemoglobin index (THI) HbO2 was calculated. Blood pressure, StO2 and HbO2 values at the beginning and immediately after blood donation(BD) were calculated. The ischemic stress test was performed by occluding the brachial artery by a sphygmomanometer cuff inflated 50mmHg over systolic blood pressure for 3 minutes. Pre- defined variables were calculated out of the recorded StO2 and HbO2 values. To detect a difference in variable before and after blood donation, the non-parametric Wilcoxon matched-pairs signed-ranks test was used.
Results: Median age was 30.5 yrs (range 19–62), median body weight 58 kg (range 50–65). There was a significant decrease in systolic blood pressure (BP) from 121.8 ± 9.9 (mean ± SD) to 112.8 ± 10.7 (p<0,0001). However variables measured by NIRS did not change significantly: StO2 79.3 ± 5.0% to 78.6 ± 5.3% (p = 0.35); HbO2 1067.5 ± 162.8 to 1056.8 ± 176.6; (p = 0,44). Variables measured after ISST did not change significantly, too: StO2 slope of recovery 3.0 ± 0.8%/sec to 3.1 ± 0.6%/sec (p = 0,26); HbO2 slope of recovery 59.2 ± 17.9/sec to 61.6 ± 13.6/sec (p = 0.6); delta StO2 13.7 ± 3.1% to 14.6 ± 4.1% (p = 0.4). There was a trend in delta HbO2 429.5 ± 153.9 to 468.5 ± 129.0 (p = 0.058). The study was underpowered to show a possible significant change.
Conclusion: Although systolic blood pressure decreased significantly after blood donation of 500ml, StO2 did not show any significant change in baseline. Furthermore, there were no significant changes after ischemic stress tests. Only HbO2 increased nearly significantly after blood donation. In order to understand the physiological background of these findings, more systematic research is needed.