Introduction The Japanese Red Cross Tokyo Blood Center collects approximately 600 000 blood donations every year. Since we experienced a fatal injury case related to vasovagal reaction (VVR) syncope in 2005, we conducted a cross-sectional study to elucidate factors contributing to VVR, the most frequent side effect, following whole blood and apheresis donations.

Methods Complications recorded at the collection sites after voluntary donations by Japanese Red Cross Tokyo Blood Center, in the 2006 and 2007 fiscal years, were analysed by univariate and multivariate logistic regression model. Of 1 119 716 blood donations over a full 2 years, complications were recorded for 13 320 donations (1.189%), among which VVR was the primary or secondary complication in 67%. Eligible 4303 VVR cases having sufficient information, and 40 256 control donors were prepared. Age, body mass index, predonation blood pressure, pulse, and biomarkers (eg, total protein, albumin, and haemoglobin) were compared between VVR group and control group.

Results VVR group was significantly younger, lower body mass index, lower blood pressure, higher biomarkers' values (eg, total protein, albumin, and haemoglobin) than control group. (p<0.001) Furthermore, biomarkers' values and VVR incidences showed a dose-dependent manner. (Trend test p<0.01).

Conclusion Obviously, to prevent serious consequences, donors should be informed about importance of rest afterwards, and posture to take when symptoms occur. From our analysis, extra care should be considered including high biomarkers' concentrations (eg, total protein, albumin, and haemoglobin), which might reflect donor's dehydration state.