Vasovagal reactions among blood donors - incidence, mechanisms, risk factors, implications and preventive measures - a literature study

Abstract

Background/objective: Blood donation is considered to be a safe procedure, however, sometimes vasovagal reactions (VVRs) with various degrees of severity can occur. This paper provides an overview of the incidence of VVR with a focus on vasovagal syncope (VVS, temporary loss of consciousness), risk factors, and possible consequences of VVR/VVS for donors, as well as effects of interventions that are used to reduce VVR/VVS among blood donors. We also discuss mechanisms underlying VVS and evolutionary explanations for VVS. Methods: Relevant studies were found by search in PubMed. Results: Reported incidence of VVS varies from 0.1% to 0.5%, with higher incidence among younger and first-time donors, but mixed results have been found for gender differences: whereas some studies report higher incidence among female donors, other studies find no differences. Anxiety, fear of needles or seeing blood are frequent triggers of VVR/VVS, particularly among first-time donors. Donors who have experienced VVR/VVS are less likely to return to donate. Physiologic interventions such as pre-donation water intake and applied muscle tension during donation, alone or in combination, have shown effect in reducing VVR/VVS in several studies. Psychological interventions such as distraction and social support have also shown to reduce the risk of VVR/VVS. From an evolutionary perspective, VVS may have had a survival advantage in the distant past.

Keywords

• blood donation
• vasovagal syncope
• baroreceptor
• first-time donor