ABSTRACT
BACKGROUND: All studies of vasovagal syncope (VVS) after blood donation have been performed with civilian donors. We hypothesized that military donors have a lower incidence of VVS and a particular set of predisposing factors. STUDY DESIGN AND METHODS: Retrospective case-control study matching every case of VVS seen from 2011 to 2019 with two controls without VVS from the same blood drive. We used the odds ratio (OR) and its 95% confidence interval (CI), estimated by multivariate logistic regression, to identify independent predictors of VVS. RESULTS: There were 105 episodes of VVS among 65.481 whole blood donations (0.15%). VVS was more frequent among donors from military academies than from other military units (0.37% vs. 0.10%, p < .001) and in collections conducted in mobile inside setups than in mobile buses (0.23% vs. 0.06%, p < .001). In the multivariate analysis, the only independent predictors of VVS were the status of first-time donor (OR 2.6, 95% CI 1.5-4.4; p < .001) and pre-donation systolic blood pressure (SBP) < 120 mm Hg (OR 1.9, 95% CI 1.1-3.3; p = .01). Donors with both risk factors had a 5.5-fold increased risk of VVS than donors without any risk factor. Age and female sex were not predictive of VVS. DISCUSSION: Active duty military blood donors have a lower incidence of VVS than that reported in civilian donors. First-time donors and donors with SBP < 120 mm Hg should be temporarily deferred when immediate reincorporation to hazardous or strenuous duty tasks after donation is inescapable.
