BACKGROUND: Whole blood donation in the United States is restricted in volume to 10.5 mL/kg or less in an effort to prevent hypovolemic reactions, but still may exceed more than 15% of a donor's estimated blood volume (EBV). We analyzed the association of EBV with prefaint and systemic vasovagal reactions (SVRs) among whole blood donors and the potential impact of an EBV-based deferral policy.

STUDY DESIGN AND METHODS: Independent predictors for prefaint reactions and SVRs were assessed by multivariate logistic regression analysis on 591,177 unique donors participating in the Retrovirus Epidemiology Donor Study-II study.

RESULTS: Young age (16 years old odds ratio [OR], 3.70; 95% confidence interval [CI], 2.78-4.94), low EBV (<3.5 L OR, 3.30; 95% CI, 2.57-4.23), and first-time donation status (OR, 2.33; 95% CI, 2.03-2.67) were the strongest predictors for SVRs, with similar trends seen for prefaint reactions. Sex, height, race, blood center, and donation site were weakly associated predictors. A total of 5.6% of all donors had an EBV of less than 3.5 L and experienced 12.5% of all prefaint reactions and 14.5% of SVRs. The highest reaction rates were seen in donors less than 23 years old with an EBV of less than 3.5 L who comprised 2.7% of all donors, who were mostly female (99.9%), and who experienced 8.8% of prefaint reactions and 11.0% of SVRs.

CONCLUSION: Young age, low EBV, and first-time donation status are the major correlates of prefaint reactions and SVRs, suggesting that high school and college donors are at particular risk. Deferral of donors with low EBV who are less than 23 years old may offer a rational approach to protecting donors at greater risk of reactions without jeopardizing the adequacy of the blood supply.