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Title: Prevention of vasovagal reactions in blood donors
Authors: Cheung, Cara Hor Yine
Degree: Ph.D.
Issue Date: 2021
Abstract: Vasovagal reaction (VVR) is the most common adverse reaction during blood donation that may cause harm. Donors with VVR are less likely to return to donate again. Both physiological and psychological components contribute to the development of VVR during blood donation. The current knowledge on the physiological mechanism is insufficient in addressing the efficacy of different prevention methods. This project aimed to systematically address the effects of fluid prehydration and applied muscle tension (AMT) in mitigating the incidence of VVR in young blood donors. Two double-blinded randomized controlled trials were performed to investigate the effects of prehydration fluids. Each study cohort was equally allocated into 3 groups: (1) Standard management (no prehydration), (2) 500 mL of flavoured water and (3) 500 mL flavoured isotonic fluid (ORS). We were unable to show a statistically significant reduction in the incidence of VVR in donors given fluid prehydration when compared to no prehydration. However, oral prehydration with water or ORS shortly before blood donation was capable of expanding the intravascular volume with an increase in stroke volume (SV). The reduction in SV and cardiac output (CO) from phlebotomy was less in the ORS group compared to water group, with the ORS group capable of restoring the CO to the predonation level after phlebotomy. This finding suggested a longer duration of action with the ORS. There was a trend showing that donors given ORS experienced a milder degree of vasovagal symptoms associated with delayed VVR, although not reaching statistical significance. A major reason to account for this is our sample size estimation, which was based on the prevailing rate of 15.7% and the lower incidence of VVR recorded in the control group, rendered the study underpowered to demonstrate a significant difference.
The haemodynamic effects of AMT were also evaluated in first-time donors. Practicing AMT improved the haemodynamic profile during phlebotomy when compared to those that did not practice AMT. During recovery, SV and CO were higher and systemic vascular resistance (SVR) was lower in the AMT group even though it was not statistically significant. The adverse effects associated with delayed VVR were less severe in donors practicing AMT. Based on 3 prediction models developed using machine learning algorithms, we identified 5 risk factors associated with VVR from our exploratory study. These features include (i) percentage of volume loss; (ii) State-Trait Anxiety Index scores; (iii) predonation systolic blood pressure; (iv) age and (v) gender. We have attempted to address the efficacy of fluid prehydration and AMT in mitigating the incidence of VVR. Using ORS prehydration or practicing AMT reduces the haemodynamic deterioration resulting from phlebotomy, suggesting their potential beneficial effects. Blood donors are recommended to employ these techniques during blood donation in order to mitigate the incidence of VVR association with blood donation.
Subjects: Syncope (Pathology)
Blood donors
Hong Kong Polytechnic University -- Dissertations
Pages: xx, 265 pages : color illustrations
Appears in Collections:Thesis

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