The efficacy and effectiveness of drinking interventions to reduce vasovagal reactions in blood donors: A systematic review and meta‐analysis

Abstract Background and Objectives Blood establishments strive to ensure the safety and comfort of blood donors while minimizing adverse events. This review aims to assess the efficacy and effectiveness of eating and/or drinking interventions before, during and/or after blood donation in reducing vasovagal reactions (VVRs). Materials and Methods We analysed randomized and non‐randomized controlled trials comparing eating and/or drinking interventions to no intervention, placebo or usual practice on (pre‐)syncopal VVRs and related symptoms. The GRADE (Grading of Recommendations, Assessment, Development and Evaluation) approach was used to assess the risk of bias and overall certainty of the evidence. Results Pre‐donation water ingestion likely results in reduced on‐site VVRs, compared to no water (2 fewer per 100 donors, moderate‐certainty evidence). A pre‐donation isotonic drink likely results in reduced VVRs, compared to usual practice (2 fewer per 100 donors, moderate‐certainty evidence). Pre‐donation salt‐loaded sweetened lemon water may result in fewer off‐site VVRs, compared to sweetened lemon water only (1 fewer per 100 donors, low‐certainty evidence). Pre‐donation water and a gel cap containing sucrose with 250 mg caffeine may result in fewer blood donor reaction ratings, compared to pre‐donation water only (low‐certainty evidence). Conclusions Pre‐donation plain water ingestion or isotonic drink probably results in a large reduction in on‐site and off‐site VVRs. Pre‐donation water ingestion with caffeine consumption or salt supplementation may result in a VVR reduction, compared to water ingestion only. Future large trials are required to increase the certainty of the effect of these and other interventions in the prevention of VVRs.