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with a relatively inexperienced phlebotomist than a more experienced one. The importance of the phlebotomist in the experience of VVRs was echoed in the results of Stewart et al. (2006) who documented a reduction in VVR as a function of the phlebotomist’s social skills. Kaspirin et al. (1992) explored the relationship of wait times to VVR and reported a positive correlation between the two. Donors who waited more than 60 minutes from registration to the beginning of phlebotomy had a frequency of reactions nearly four times that of those who waited 19 minutes or less. More recent analyses suggest that the duration of the actual donation also has an impact. France et al. (2016), This article is protected by copyright. All rights reserved. 9 in a further exploration of donor fear of the blood draw, found that the overall proportion of officially recorded VVRs increased with increases in draw time. However, for all draw times, fear of the blood draw remained the single best predictor of VVR. Considering the impact of the ‘social’ aspect of blood donation, Ditto and colleagues (2014) showed a positive association between seeing another donor being treated for VVR symptoms and self-report of VVR symptoms using the BDRI in non first-time blood donors. Further, observing a donor being treated for VVR was associated with a slower rate of return in the following two years in first-time donors. Whether an individual donor will experience a VVR or VVR symptoms cannot be determined when that person presents to donate. VVR risk factors can be identified through large-scale BCA database analyses and the inclusion of information reported by the donor, such as fear and anxiety. Further, how that donor is treated once they are in the donation centre may also impact on whether VVR symptoms result. Accepting that the evidence base for the predictive value of subjectively reported risk factors (e.g., fear, anxiety, donor experience) is less comprehensive than that for objectively measured risk factors, the analysis by France and colleagues (2013) provides an interesting insight into the potential interplay between demographic features and psychological characteristics of the donor. However, the fact remains that large-scale analyses using rigorous methodologies that take into account both observable and unobservable characteristics of donors and contextual features of the donation environment have not yet been conducted. Such largescale analyses would allow us to determine the profile of our most vulnerable donors and the This article is protected by copyright. All rights reserved. 10 contextual features that may protect them from experiencing a VVR. In the absence of this, strategies to prevent VVR are currently recommended for all donors. Preventing vasovagal reactions The potential underlying mechanisms of VVRs include the orthostatic effects on a hypovolemic static state following a donation (i.e. the drop in blood pressure when getting out of the donation chair), and the psychological stress associated with the procedure (e.g., sight of the needle or phlebotomy-related pain) (Wieling et al. 2011a). Due to the complexity of the underlying mechanisms of VVRs, current prevention strategies target either physiological or psychological aspects of the reaction. Physiological strategies The effects of a variety of physiological prevention interventions on VVRs have been assessed through a number of randomised controlled trials in blood donation settings. The primary objective of these interventions is to prevent the sudden drop in blood pressure which causes the donor to experience VVR symptoms. Within this intervention literature, the main focus has been on the efficacy of two techniques – pre-donation water loading and applied muscle tension (AMT) – enacted in centre to prevent VVRs. Fisher and colleagues (2016) recently considered the results of five randomised controlled trials exploring the effect of pre-donation water loading (ingesting 500mL of water within 30 minutes) This article is protected by copyright. All rights reserved. 11 on VVRs. Overall, donors who water loaded prior to donation were observed by the phlebotomist or researcher to have a significantly lower relative risk of experiencing a VVR in comparison to the control groups, who mainly received no treatment.

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