Hydrate to donate: How simple drinks can prevent fainting in blood donors

18/09/24

Vasovagal reactions are common adverse events during or after blood donations, manifesting as dizziness, fainting, or loss of consciousness. These reactions are problematic for blood donation centres because they can deter first-time donors from returning and pose safety risks for donors after leaving the facility.

We conducted a systematic review and meta-analysis of randomized and non-randomized controlled trials to assess the impact of drinking interventions on reducing the incidence of vasovagal reactions. The trials compared drinking water, isotonic drinks, and other interventions before, during, or after blood donation with no intervention or standard practices.

Key findings from the review suggest that pre-donation water consumption (250-500 mL) likely reduces the number of on-site vasovagal reactions by about two per 100 donors. Similarly, the ingestion of isotonic drinks before donating blood may also lead to a reduction in vasovagal reactions, particularly in off-site reactions that occur after leaving the donation centre.

Additional findings from individual studies included the potential benefit of adding caffeine or salt to pre-donation water. For instance, water with 250 mg of caffeine showed some promise in reducing vasovagal reactions, although the evidence was not as strong. Similarly, adding salt to a sweetened lemon drink may help prevent off-site vasovagal reactions, particularly in certain subgroups such as young or female donors.

Overall, this review concludes that drinking plain water or isotonic drinks before blood donation is a simple and effective method to reduce vasovagal reactions, with some potential benefits from adding caffeine or salt. However, the authors also note that more research is needed, particularly large randomized controlled trials, to confirm the effectiveness of these interventions and explore additional strategies to prevent vasovagal reactions in blood donors.

The findings from this review are significant for blood collection agencies as they suggest cost-effective and easily implementable interventions that could improve donor retention and reduce adverse events, thereby contributing to a safer and more comfortable donation experience.