Effects of pre‐donation salt‐loading on the occurrence of delayed vasovagal reactions

BACKGROUND AND OBJECTIVES: Vasovagal reaction (VVR) is the most frequent adverse reaction in blood donation, which usually recovers soon without complications. However, syncopal VVR can result in severe injury due to a fall. Some reports have shown the possibility to prevent VVR with salt-loading prior to blood donation. This semi-randomized controlled study aims to clarify the preventive effect of salt-loading on VVR among whole blood (WB) donors. MATERIALS AND METHODS: During the study period, donors who donated 400 mL of WB on odd days were assigned to the salt-loading group and those who donated on even days to the control group. Participants in the salt-loading group were asked to take three tablets containing 0.3 g salt in total. RESULTS: The incidence of VVRs occurring >20 min after needle removal (delayed VVR [dVVR]) did not significantly differ between the two groups. Secondary analysis suggested a possible dose-dependent preventive effect against dVVR (odds ratio [OR]: 0.70; 95% confidence interval [CI]: 0.52-0.94; p = 0.02). The number of delayed syncopal VVR episodes in summer was lower in the salt-loading group than in the control group (n = 1 vs. 8; OR: 0.13; p = 0.04; pre-specified α = 0.0125). CONCLUSION: There was no significant preventive effect of pre-donation salt-loading on VVR. Further investigations with sufficient number of participants are needed to conclude the suggested dose dependency and seasonal preventive effect on dVVRs.