Prevention of syncopal-type reactions after whole blood donation: a cluster-randomized trial assessing hydration and muscle tension exercise

Abstract

Background: The prevention of presyncopal and syncopal reactions to whole blood donation is important for both the donor's safety and their retention as blood donors. The best strategy to achieve this remains debated.

Study design and methods: A prospective cluster-randomized trial comparing three hydration modes (500 mL of an isotonic drink, 500 mL of water, just before phlebotomy, or advice to drink [control arm]) coupled or not with light muscle tensing exercises, was carried out in mobile and fixed units of two regional blood centers in southeast France between January and July 2014. The main outcome was the cumulative incidence of presyncope (feeling faint) and syncope (fainting) at the donation site or in the 48 hours after leaving the site. Secondary outcomes were the cumulative incidence of these adverse events during donation, immediately after blood donation, or within 48 hours.

Results: Overall, presyncope or syncope occurred in 5.5% of the 4576 donors. Compared to controls, drinking 500 mL (isotonic solution or water) significantly reduced the rate of events (odds ratio [OR], 0.74; 95% confidence interval [CI], 0.55-0.99; p = 0.041) independently of muscle tensing exercise. Muscle tensing exercises significantly reduced syncopal-type reactions during the donation (OR, 0.64; 95% CI, 0.42-0.98; p = 0.041), and an isotonic drink significantly reduced delayed off-site syncopal-type reactions (OR, 0.62; 95% CI, 0.40-0.98; p = 0.040) and tiredness after donation (OR, 0.75; 95% CI, 0.59-0.94; p = 0.014).

Conclusions: Drinking 500mL of water or isotonic drink close to phlebotomy is useful in preventing presyncopal or syncopal reactions in blood donors. Isotonic drinks have the advantage of preventing delayed reactions and tiredness after whole blood donation.