Vasovagal Reactions Research Articles

Development and validation of a scoring system to predict vasovagal reaction upon whole-blood donation.

Risk factors for vasovagal reaction (VVR) have been extensively studied. With knowledge of the relative importance of these risk factors for VVR, collection staff could take care of blood donors from the same standpoint, leading to improved donor safety. We therefore developed a scoring system to predict VVR, which incorporates registration information. Pre-syncopal and syncopal symptoms, as well as on- and off-site reactions, are included in this analysis as VVR. We defined the donor status as follows: first-time donors, repeat donors with no history of reaction and repeat donors with a history of reaction. We prepared two datasets: whole-blood donations at a blood donation site in Tokyo between January 2019 and December 2019 were included in training data (n = 361,114), and whole-blood donations between January 2020 and August 2020 were included in testing data (n = 216,211). The most important variable was the donor status, followed by age, estimated blood volume and height. We integrated them into a scoring system. Training and testing datasets were combined (n = 577,325), and VVR rates in groups with scores of 0, 1, 2, 3, 4 and 5 or more were 0.09% (95% CI: 0.081%-0.10%), 0.33% (95% CI: 0.31%-0.36%), 0.87% (95% CI: 0.78%-0.96%), 1.17% (95% CI: 1.05%-1.30%), 2.15% (95% CI: 1.98%-2.32%) and 3.11% (95% CI: 2.90%-3.34%), respectively. The scoring system enables staff to significantly predict VVR and may help them to identify donors at increased risk of experiencing syncope, thereby mitigating the negative impact of VVR on donor safety and return by paying close attention to high-risk donors.

Battlefield acupuncture for chronic musculoskeletal pain in cancer survivors: a novel care delivery model for oncology acupuncture.

Battlefield Acupuncture (BFA), a standardized auricular acupuncture protocol, is widely used for pain in the military but is not well-studied in oncology. This study examined cancer survivors who received BFA for pain. This is a secondary analysis of a randomized trial that compared the effectiveness of BFA and electroacupuncture vs. usual care for chronic musculoskeletal pain in cancer survivors. This study focused on participants randomized to BFA. Participants received 10 weekly treatments. Needles were placed until one of these stop conditions were satisfied: ten needles were administered; pain severity decreased to ≤1 out of 10; patient declined further needling, or vasovagal reaction was observed. Pain severity was assessed using Brief Pain Inventory. Responders were those with ≥30% pain severity reduction. We examined pain location, BFA stop reason, and pain reduction of participants during the first session. We also examined which factors predicted responder status after the first session (week 1) or the full treatment (week 12). Among 143 randomized to BFA, most common pain locations were lower back (30.8%) and knee/leg (18.2%). Of 138 who initiated treatment, 41 (30.0%) received ten needles; 81 (59.1%) achieved pain ≤1; 14 (10.2%) declined further needling; and 1 (0.7%) had vasovagal reaction. BFA reduced pain severity by 2.9 points (95% CI 2.6 to 3.2) after the first session (P < 0.001). After adjusting for baseline pain severity, responders at week 1 were 2.5 times more likely to be responders at week 12, compared to those who were non-responders at week 1 (AOR 2.5, 95% CI 1.02 to 6.11, P = 0.04). Among those who achieved pain ≤1, 74% were responders at week 12, a higher proportion compared to the proportion of responders among those who received ten needles (39.5%), those who declined further needling (50%), and those with vasovagal reaction (0.0%) (P = 0.001). Those with pain in proximal joints had a higher proportion of responders at week 12, compared to those with pain in distal joints (64.2% vs. 20%, P = 0.008). Specific factors may predict the likelihood of achieving meaningful pain reduction from BFA. Understanding these predictors could inform precision pain management and acupuncture delivery models.

Robotic-assisted percutaneous coronary intervention: experience in Switzerland.

Percutaneous coronary intervention (PCI) exposes operators to ionizing radiation. Robotic-assisted PCI (RA-PCI) is a novel technology that enables interventional cardiologists to operate coronary devices remotely from a radiation-shed cockpit. The aim of this study is to describe the experience and challenges during the initiation of a RA-PCI program and to report outcomes of the first 21 patients undergoing RA-PCI in Switzerland. All patients undergoing RA-PCI using the CorPath GRX Vascular Robotic System between 06/2021 and 12/2021 at Inselspital, Bern University Hospital were included in this retrospective registry study. Baseline, procedural and clinical follow-up data were prospectively assessed as part of the Cardiobase Bern PCI registry (NCT02241291). The two endpoints of interest were clinical success [defined as <30% residual diameter stenosis in the absence of in-hospital major adverse cardiovascular events (MACE: composite of death, periprocedural myocardial infarction, target-vessel revascularization, and stroke)] and robotic success (defined as clinical success and completion of RA-PCI without or with partial manual assistance). Additional outcome measures include clinical long-term outcomes at one year. Twenty-five lesions in 21 patients were treated with RA-PCI (age 62.4 ± 9.1 years, 24% female). Clinical success was achieved in 100%, and robotic success in 81% (17/21 procedures, including 4 procedures requiring partial manual assistance). Manual conversion (e.g. manual completion of the procedure) occurred in 19% (4 procedures). Reasons for manual assistance or conversion were poor guiding-catheter back-up or platform limitations (4), adverse events (2x transient slow-flow that was solved manually), safety decision (1x vasovagal reaction not related to robotic approach), and software error (1). No in-hospital MACE occurred. During 12 months of follow-up, one patient suffered a non-target-vessel myocardial infarction requiring repeat PCI. RA-PCI can safely be performed without clinically relevant robot-associated complications in selected patients with approximately 80% of procedures conducted without or with partial manual assistance.

Ultrasound-Guided vs. Fluoroscopy-Guided Interventions for Back Pain Management: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

The objective of this study was to compare the outcomes of the ultrasound- and fluoroscopy-guided techniques in the management of back pain. Using PubMed, Scopus, and the Cochrane Library, we searched randomized controlled trials (RCTs) published before May 2023, which reported relevant data on the topic. The effectiveness of the ultrasound-guided (US-guided) and fluoroscopy-guided (FL-guided) approaches for back pain management was compared in terms of postoperative pain intensity, postoperative functional outcomes, and postoperative complications. Subgroup analyses were conducted for different postoperative periods. Eight studies were included in the analysis. There was no significant difference in post-procedural pain relief at one week, two weeks, one month, two months, and three months between the US-guided and FL-guided interventions for back pain management (SMD with 95% CI is -0.01 [-0.11, 0.10]), p = 0.91, I2 = 0%). In terms of the postoperative functional outcomes assessed by the "Oswestry Disability Index" (ODI) functionality score, the model tends to favor the FL-guided injections over the US-guided injections (SMD with 95% CI: 0.13 [-0.00, 0.25], p = 0.05, I2 = 0). Finally, the US-guided and FL-guided injections did not show significantly different results in terms of postoperative complications (RR with 95% CI is 0.99 [0.49, 1.99], p = 0.97, I2 = 0). The subgroup analysis also did not demonstrate differences between the US-guided and FL-guided techniques in the following outcomes: vasovagal reaction, transient headache, and facial flushing. There was no significant difference between the US-guided and FL-guided injections for treating back pain in terms of postoperative pain intensity and complications. Still, the model tends to favor the FL-guided injections over the US-guided injections in terms of functionality.

Patient satisfaction, safety, and efficacy of nurse-led compared to physician-led implantation of cardiac monitors.

Implantation of an implantable cardiac monitor (ICM) is a simple procedure, but adds significant and increasing workload to the arrhythmia service. In 2020, we established a nurse-led ICM implantation service. We aimed to analyse patient satisfaction, adverse events during implant, and ICM re-interventions with nurse-led ICM implantation (N-Implant) compared to physician-led ICM implantation (P-Implant). From January 2020 to December 2021, we included all consecutive patients implanted with an ICM in a prospective registry. We collected data on patient characteristics, implant procedure, and follow-up. Patients were interviewed by phone four weeks after ICM implantation.Of 321 patients implanted with an ICM (median age 67 years; 33% women), 189 (59%) were N-Implants. More N-Implants were performed in the outpatient clinic compared to P-Implants (95% vs. 8%; P < 0.001). Two N-Implant patients experienced vaso-vagal reaction during implantation (1%), whereas no adverse events occurred during P-Implant (P = 0.51). A total of 297 patients (93%) completed the questionnaire. Duration of pain was shorter and wound closure after 2 weeks better following N-Implant (P = 0.019 and P = 0.018). A minor bruise or swelling at the implant site was reported more frequently after N-Implant (P = 0.003 and P = 0.041). Patient satisfaction was excellent with both N-Implant and P-Implant (99% and 97%; P = 0.16). After a median follow-up of 242 days (range 7-725 days), five ICMs (2%) were explanted prematurely, without differences among groups. Reasons for premature explants were local discomfort (n = 2), infection, MRI, and ICM malfunction. Nurse-led ICM implantation has excellent patient satisfaction without compromising safety. N-Implant both expands nursing competencies and reduces physician workload.

P‐BB‐11 | Analysis of Donor Moderate and Severe Vasovagal Reactions During Donation on the Alyx Collection Device

P‐BB‐11 | Analysis of Donor Moderate and Severe Vasovagal Reactions During Donation on the Alyx Collection Device

P‐BB‐39 | Frequency of Vasovagal Reactions with Large‐Volume Plasma Donations in Canada

P‐BB‐39 | Frequency of Vasovagal Reactions with Large‐Volume Plasma Donations in Canada

Blood Donors Hemovigilance in Public Sector Tertiary Care Hospitals of Peshawar

Hemovigilance of blood donors is an integral part of blood transfusion system, conferring to lessen the blood donation complications and enhancing the safety of blood donors. Objective: To determine the prevalence, severity, and associated factors of acute hemovigilance reactions in the blood donors of public sector tertiary care hospital bank banks in Peshawar. Methods: A multi-centered, cross-sectional approach was applied on blood donors` population selected via random proportionate sampling, visiting 6 Public sector tertiary care hospitals in Peshawar. Adverse reactions were reported on national guidelines reporting form during and after the blood donation. Results: Out of 420 blood donors selected via random proportionate sampling of total blood donors` population, prevalence of acute adverse hemovigilance reaction was 8.57% while no adverse reactions occurred in 91.43% of the blood donors. The most frequent hemovigilance reaction was vasovagal reactions (5.2%). All the reactions were of mild to moderate severity with no life threatening hemovigilance reactions. Conclusions: The overall prevalence rate was 8.57% of all healthy blood donors` which strengthens the fact that adverse reactions are avoidable complication of blood donations among the voluntary and replacement blood donors, and can be prevented with centralized hemovigilance data base for a sustainable base of voluntary blood donors.

A donor safety evidence literature review of the short- and long-term effects of plasmapheresis.

Many blood establishments are expanding plasmapheresis collection capacity to achieve increasing plasma for fractionation volume targets, driven by immunoglobulin product demand. Some adverse events occur in both apheresis and whole blood collection, such as venepuncture-related trauma and vasovagal reactions. Others are specifically related to the apheresis procedure, such as citrate reactions, haemolysis, infiltration and air embolism. Whilst plasmapheresis procedures are generally well tolerated, theoretical longer term donor health considerations, such as the effects on donor plasma protein levels, bone mineral density, iron deficiency and malignancy also require consideration. An evidence-based framework that supports a safe and sustainable increase in the collection of plasma is essential. Our review demonstrates a lack of high-quality evidence on risks and outcomes specifically in plasmapheresis. Whilst conservative procedural controls and donor harm minimization policies will mitigate risk, high-quality evidence is needed to facilitate practice change that is safe and sustainable and maximizes the potential of individual donor differences.

A new risk predictive scoring system of vasovagal reactions in patients with preoperative autologous blood donation

Background and objectivesVasovagal response (VVR) is the most common adverse reaction during blood donation and it is the main element for the safety of the patients with preoperative autologous blood donation (PABD). Accurate identification high-risk group is of great significance for PABD. Our study aimed to establish a scoring system based on the nomogram to screen the high-risk population and provide evidence for preventing the occurrence of VVRs. Materials and methodsA number of 4829 patients underwent PABD between July 2017 and June 2020 in the first medical center of Chinese PLA Hospital were recruited, 3387 of whom were included in the training group (70 %; 108 VVRs patients vs 3279 Non-VVRs patients), 1442 were included in the validation group (30 %; 46 VVRs patients vs 1396 Non-VVRs patients). The data were analyzed by univariate and multivariate logistic regression. The nomogram of the scoring system was created by using the RMS tool in R software. ResultsSeven variables including BMI, hematocrit, pre-phlebotomy heart rate and systolic blood pressure, history of blood donation, age group and primary disease were selected to build the nomogram, which was shown as prediction model. And the score was 0–1 for BMI, 0–2 for hematocrit, systolic blood pressure, heart rate and no blood donation history, 0–10 for age, 0–3 for primary disease. When the total cutoff score was 11, the predictive system for identifying VVRs displayed higher diagnostic accuracy. The area under the curve, specificity, and sensitivity of the training group were 0.942, 82.41 % and 97.17 %, respectively, whereas those of the validation group were 0.836, 78.26 % and 78.15 %, respectively. ConclusionA risk predictive scoring system was successfully developed to identify high-risk VVRs group form PABD patients that performed well.

Evaluation of interventions to prevent vasovagal reactions among whole blood donors: rationale and design of a large cluster randomised trial

BackgroundVasovagal reactions (VVRs) are the most common acute complications of blood donation. Responsible for substantial morbidity, they also reduce the likelihood of repeated donations and are disruptive and costly for blood services. Although blood establishments worldwide have adopted different strategies to prevent VVRs (including water loading and applied muscle tension [AMT]), robust evidence is limited. The Strategies to Improve Donor Experiences (STRIDES) trial aims to reliably assess the impact of four different interventions to prevent VVRs among blood donors.MethodsSTRIDES is a cluster-randomised cross-over/stepped-wedge factorial trial of four interventions to reduce VVRs involving about 1.4 million whole blood donors enrolled from all 73 blood donation sites (mobile teams and donor centres) of National Health Service Blood and Transplant (NHSBT) in England. Each site (“cluster”) has been randomly allocated to receive one or more interventions during a 36-month period, using principles of cross-over, stepped-wedge and factorial trial design to assign the sequence of interventions. Each of the four interventions is compared to NHSBT’s current practices: (i) 500-ml isotonic drink before donation (vs current 500-ml plain water); (ii) 3-min rest on donation chair after donation (vs current 2 min); (iii) new modified AMT (vs current practice of AMT); and (iv) psychosocial intervention using preparatory materials (vs current practice of nothing). The primary outcome is the number of in-session VVRs with loss of consciousness (i.e. episodes involving loss of consciousness of any duration, with or without additional complications). Secondary outcomes include all in-session VVRs (i.e. with and without loss of consciousness), all delayed VVRs (i.e. those occurring after leaving the venue) and any in-session non-VVR adverse events or reactions.DiscussionThe STRIDES trial should yield novel information about interventions, singly and in combination, for the prevention of VVRs, with the aim of generating policy-shaping evidence to help inform blood services to improve donor health, donor experience, and service efficiency.Trial registrationISRCTN: 10412338. Registration date: October 24, 2019.

FactFinders for patient safety: Preventing potential procedure-related complications: Vasovagal reactions and spinal cord stimulator lead migration

This series of FactFinders presents a brief summary of the evidence and outlines recommendations to improve our understanding and management of several potential procedure-related complications.Evidence in support of the following facts is presented. (1) Vasovagal Reactions During Interventional Pain Procedures -- The overall incidence of vasovagal reactions (VVR) ranges from 1 to 8% during interventional pain procedures, though certain patient populations may be at greater risk. Younger age, male sex, and a history of a VVR are associated with an increased likelihood of VVR. In select patients, moderate sedation may be considered for prevention of a repeat vasovagal reaction. (2) Spinal Cord Stimulator Trial Lead Migration -- Suturing percutaneous SCS leads does not mitigate the risk of migration compared to taping alone during a trial. Most lead migration does not pose a safety concern during the trial period.

Development and validation of a nomogram for predicting the risk of vasovagal reactions after plasma donation.

Vasovagal reactions (VVRs) are the most common adverse reactions and are frequently associated with serious donor adverse events. Even mild VVRs can lead to a significant reduction in the likelihood of subsequent donations. The purpose of this study is to explore the factors related to the occurrence of VVRs after plasma donation and to construct a nomogram to identify individuals at risk for VVRs to improve the safety of plasma donors. We collected the donation data from July 2019 to June 2020 from a plasma center in Sichuan, China, to explore the independent risk factors for vasovagal reactions. From these data, we constructed and validated a predictive model for vasovagal reactions. VVRs after plasma donation occurred 737 times in 120 448 plasma donations (0.66%). Gender, season, donor status, weight, pulse, duration of donation, and cycle were independent risk factors for VVRs (P< 0.05). The concordance index (C-index) of a logistic model in the derivation cohort was 0.916, with a Hosmer-Lemeshow goodness-of-fit probability of 0.795. The C-index of a logistic model in the validation cohort was 0.916, with a Hosmer-Lemeshow goodness-of-fit probability of 0.224. The calibration curve showed that the predicted results were in good agreement with the actual observed results. This study preliminarily constructed and verified a prediction model for VVRs after plasma donation. The model nomogram is practical and can identify high-risk donors.

Predicting vasovagal reactions to needles with anticipatory facial temperature profiles

Around one-third of adults are scared of needles, which can result in adverse emotional and physical responses such as dizziness and fainting (e.g. vasovagal reactions; VVR) and consequently, avoidance of healthcare, treatments, and immunizations. Unfortunately, most people are not aware of vasovagal reactions until they escalate, at which time it is too late to intervene. This study aims to investigate whether facial temperature profiles measured in the waiting room, prior to a blood donation, can be used to classify who will and will not experience VVR during the donation. Average temperature profiles from six facial regions were extracted from pre-donation recordings of 193 blood donors, and machine learning was used to classify whether a donor would experience low or high levels of VVR during the donation. An XGBoost classifier was able to classify vasovagal groups from an adverse reaction during a blood donation based on this early facial temperature data, with a sensitivity of 0.87, specificity of 0.84, F1 score of 0.86, and PR-AUC of 0.93. Temperature fluctuations in the area under the nose, chin and forehead have the highest predictive value. This study is the first to demonstrate that it is possible to classify vasovagal responses during a blood donation using temperature profiles.

Novel risk patterns of vasovagal reactions in NZ blood donations complicated by COVID-19 restrictions.

Vasovagal reactions (VVRs) are common but complex donor adverse reactions (DAEs) in blood donations. VVRs have been extensively studied with a multitude of risk factors identified including young age, female gender and first-time donor status. How they may interplay remains obscure. A total of 1,984,116 blood donations and 27,952 immediate VVRs (iVVRs) and 1,365 delayed VVRs (dVVRs) reported between 2011 and 2021 in NZ were used in multivariate logistic regression analyses each concerning donations with iVVRs as cases and those free of DAEs as controls. For each analysis stepwise selection was used to identify the best model and risk factors carrying significant main effects and/or interactions. Identified interactions informed further in-depth regression analyses to dissect iVVR risk patterns. Over 95% of VVRs were iVVRs that had lower female preponderance and deferrals than dVVRs. iVVRs had a school seasonal pattern in whole blood donations driven by first-time donors from schools/colleges, and interactions between gender and age group differentiating the first-time from repeat donations. Subsequent regression analyses identified the known and novel risk factors of year and mobile collection sites and their interactions. iVVR rates were roundly elevated in 2020 and 2021 probably because of COVID-19 restrictions like facemask wearing. Exclusion of the 2020 and 2021 data removed the interactions with year, but confirmed interactions of gender with mobile collection sites (p = 6.2e-07) in first-time donations only and with age group in repeat donations only (p < 2.2e-16), together indicating young female donors at the highest risk of iVVRs. Our results also revealed that donation policy changes contributed to the year effects; donors had a lower iVVR risk at mobile sites than well-medicalized donation centers probably because of under-reporting. Modeling statistical interactions is valuable in identifying odds and revealing novel iVVR risk patterns and insights into blood donations.

Prevalence and factors associated with vasovagal reaction among whole blood donors in hospital Universiti Sains Malaysia.

Adverse donor reactions (ADR) are common to occur during the blood donation process. The most common is vasovagal reactions (VVR) and it cause negative impact in the donor return rate. The aim of this study is to determine the prevalence of VVR among blood donors and to study its associated factors, at Hospital University Sains Malaysia (USM). This retrospective case-control study was conducted from June 2018, until June 2021. Data was extracted from the blood bank database system and from donor adverse reaction form. Donors who developed adverse donor reactions were chosen and without VVR were chosen at random as controls. A total of 159 donors, out of 35 134 donors were reported to have VVR which resulted in an overall prevalence of 0.45%. Dizziness or mild VVR were the most frequently observed adverse reactions, accounting for approximately 87/159 (54.7%) of all adverse reactions. Multiple logistic regression (MLR) analysis showed VVR were significantly associated with age, female gender, first-time donor, and 450ml volume of blood collected. The prevalence of vasovagal reactions among blood donors in this study was low which was similar to a few previous studies. Although it was low, still it is very important to reduce risks to a minimum so that the donor return rate could be maintained. The information regarding its associated factors can be used to identify high-risk donors to prevent the incidence in the future.

Contralateral oblique view can prevent dural puncture in fluoroscopy-guided cervical epidural access: a prospective observational study

IntroductionAlthough the contralateral oblique (CLO) view at 50°±5° is clinically useful for cervical epidural access, no previous studies have confirmed its safety. This prospective observational study was conducted to assess...

The safety of plasma apheresis from donors recovering from COVID-19 infection in Japan

PurposeSince 2020, the novel coronavirus infection (COVID-19) has spread globally. A few studies have investigated the safety of COVID-19 convalescent plasma (CCP) apheresis from COVID-19. This study was the first retrospective observational study of CCP in Japan. MethodsWe recruit donors from April 2020 to November 2021 and plasmapheresis in our center (NCGM: national center for global health and medicine). We set the primary endpoint as the Donors Adverse Event (DAE) occurrence at the time of the CCP collection. Variable selection was used to explore the determinants of DAE. ResultsMean and SD age was 50.5 (10.6) years old. Seventy-three (42.2 %) were female, and 87 (33.3 %) were multiple-times donors. Twelve (6.97 % by donors and 4.6 % in total collections) adverse events occurred. The DAEs were VVR (Vaso Vagal Reaction), paresthesia, hypotension, agitation, dizziness, malaise, and hearing impairment/paresthesia. Half of them were VVR during apheresis. DAE occurred only in first-time donors and more in severe illnesses such as using ventilation and ECMO. From the donor characteristics and variable selection, the risk factors are as follows: younger age, female, the severity of disease at the time of the disease, and lower SBP before initiation. Our DAE incidence did not differ from previous studies. DAEs were more likely to occur in CCP apheresis than in healthy donors. ConclusionWe confirm the safety of CCP apheresis in this study, although DAEs were more than healthy donors. More caution should be exercised in the plasma collection for future outbreaks of emerging infectious diseases.

Collapse of inferior vena cava during complex filter retrieval with consequent intra-procedural systemic hypotension and bradycardia: a case report

BackgroundProlonged dwelling time of inferior vena cava (IVC) filters has been shown to increase the need for the use of complex IVC filter retrieval techniques. In this report, we describe a case of complex retrieval of an IVC filter with prolonged dwelling time, which was temporarily accompanied by severe bradycardia and hypotension.Case presentationFifty-nine-year-old male patient past medical history of morbid obesity, atrial fibrillation status post-ablation, obstructive sleep apnea, and end-stage renal disease presented for IVC filter retrieval 16 years after placement. When the IVC filter was covered by sheaths, and the IVC was temporarily collapsed and occluded, the patient developed severe bradycardia and hypotension without compensatory tachycardia. Contrast injection through the common femoral vein sheath showed complete occlusion of IVC while the IVC filter was covered by both sheaths, likely due to the embedment of the IVC filter in the wall by extensive fibrinous tissues. IVC filter was successfully retrieved, and the blood pressure and heart rate were improved immediately afterward. A large non-occlusive IVC thrombus was identified on the final venogram, which was aspirated using a mechanical thrombectomy device.ConclusionComplex retrieval of IVC filters with prolonged dwelled time can result in acute severe bradycardia and hypotension due to vasovagal reaction, acute collapse, and occlusion of IVC in the setting of IVC filter embedment in the wall by extensive fibrinous tissues.

Predicting Vasovagal Reactions to Needles from Facial Action Units

Merely the sight of needles can cause extreme emotional and physical (vasovagal) reactions (VVRs). However, needle fear and VVRs are not easy to measure nor prevent as they are automatic and difficult to self-report. This study aims to investigate whether a blood donors' unconscious facial microexpressions in the waiting room, prior to actual blood donation, can be used to predict who will experience a VVR later, during the donation. The presence and intensity of 17 facial action units were extracted from video recordings of 227 blood donors and were used to classify low and high VVR levels using machine-learning algorithms. We included three groups of blood donors as follows: (1) a control group, who had never experienced a VVR in the past (n = 81); (2) a 'sensitive' group, who experienced a VVR at their last donation (n = 51); and (3) new donors, who are at increased risk of experiencing a VVR (n = 95). The model performed very well, with an F1 (=the weighted average of precision and recall) score of 0.82. The most predictive feature was the intensity of facial action units in the eye regions. To our knowledge, this study is the first to demonstrate that it is possible to predict who will experience a vasovagal response during blood donation through facial microexpression analyses prior to donation.