Classification of vasovagal syncope from physiological signals on tilt table testing.

BACKGROUND: The diagnostic test for vasovagal syncope (VVS), the most common cause of syncope is head-up tilt test (HUTT) assessment. During the test, subjects experienced clinical symptoms such as nausea, sweating, pallor, the feeling of palpitations, being on the verge of passing out, and fainting. The study's goal is to develop an algorithm to classify VVS patients based on physiological signals blood pressure (BP) and electrocardiography (ECG) obtained from the HUTT. METHODS: After 10 min of supine rest, the subject was tilted at a 70-degree angle on a tilt table for approximately a total of 35 min. 400 µg of glyceryl trinitrate (GTN) was administered sublingually after the first 20 min and monitoring continued for another 15 min. Mean imputation and K-nearest neighbors (KNN) imputation approaches to handle missing values. Next, feature selection techniques were implemented, including genetic algorithm, recursive feature elimination, and feature importance, to determine the crucial features. The Mann-Whitney U test was then performed to determine the statistical difference between two groups. Patients with VVS are categorized via machine learning models including Support Vector Machine (SVM), Gaussian Naïve Bayes (GNB), Multinomial Naïve Bayes (MNB), KNN, Logistic Regression (LR), and Random Forest (RF). The developed model is interpreted using an explainable artificial intelligence (XAI) model known as partial dependence plot. RESULTS: A total of 137 subjects aged between 9 and 93 years were recruited for this study, 54 experienced clinical symptoms were considered positive tests, while the remaining 83 tested negative. Optimal results were obtained by combining the KNN imputation technique and three tilting features with SVM with 90.5% accuracy, 87.0% sensitivity, 92.7% specificity, 88.6% precision, 87.8% F1 score, and 95.4% ROC (receiver operating characteristics) AUC (area under curve). CONCLUSIONS: The proposed algorithm effectively classifies VVS patients with over 90% accuracy. However, the study was confined to a small sample size. More clinical datasets are required to ensure that our approach is generalizable.

Prevention strategies for vasovagal reaction in whole blood donors: A quadri-armed randomised control trial.

INTRODUCTION: Vasovagal reaction (VVR) is a frequently encountered generalised donor adverse reaction, associated with donor deterrence towards future donation. Several mitigation strategies for prevention of VVR were tried but still not standardised. This quadri-armed randomised study evaluated the utility of water ingestion, applied muscle tension (AMT) and combination of both in preventing the VVR among blood donors. METHODS: A quadri-armed randomised controlled trial was performed on 4320 whole blood donors. Blood donors of 18-65 years of age were randomised into four groups based on the interventions performed i.e., control with no intervention (Group 1, n = 1081), water ingestion (Group 2, n = 1082), AMT (Group 3, n = 1070) and combined intervention (Group 4, n = 1087). VVR during and immediately after blood donation were observed along with assessment of risk factors in blood donors and the effectiveness of interventions were analysed. RESULTS: The incidence of VVR observed 1.6% in our study, with the highest occurrence in the control group (2.5%) and the lowest in the combined intervention group (0.9%). Multivariable logistic regression revealed that the control group donors faced a 1.38-fold greater risk of VVR compared to those receiving interventions (OR: 1.38, 95% CI: 1.10-1.75). Other risk factors included younger age (OR: 1.5, 95% CI: 1.05-2.17), first-time donation (OR: 5.7, 95% CI: 1.66-5.74), prior history of VVR (OR: 2.5, 95% CI: 10.4-101.52). DISCUSSION/CONCLUSION: The combined approach of water ingestion and AMT proved significantly more effective in VVR prevention compared to individual interventions.

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

BACKGROUND AND OBJECTIVES: 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. MATERIALS AND METHODS: 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). RESULTS: 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. CONCLUSION: 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.

Cardioneuroablation for the Treatment of Vasovagal Syncope: Current Status and Impact on Quality of Life.

PURPOSE OF REVIEW: Vasovagal syncope (VVS) is a common entity causing transient loss of consciousness and affecting quality of life. Guideline-recommended therapy involves conservative measures and pacing in selected patients. Cardioneuroablation (CNA) targeting the ganglionated plexi in the heart has been shown to reduce excessive vagal excitation, which plays a major role in the pathophysiology of VVS and functional bradycardia. RECENT FINDINGS: The introduction of CNA has fueled research into its value for the treatment of VVS. Multiple observational studies and one randomized trial have demonstrated the safety and efficacy of CNA and the positive impact on quality of life. This review describes the rationale and CNA procedural techniques and outcomes. Patient selection and future directions have also been described. Cardioneuroablation is a promising treatment for patients with recurrent VVS and functional bradycardia. Further large-scale randomized studies are needed to further verify the safety and efficacy of this approach.

High spinal cord injury precipitating syncope: a rare indication for pacemaker insertion.

The current evidence for vasovagal syncope management is that cardiac pacing is only indicated in a highly select group of patients where symptoms can be linked to bradycardic episodes. High spinal cord injury can lead to autonomic dysfunction and sympathetic nervous system hypoactivity. A high spinal cord injury can theoretically precipitate profound bradycardia leading to haemodynamic instability and syncope. A patient in his 50s with a history of C2 spinal injury was admitted to our tertiary centre for management of what was initially thought to be septic shock causing hypotension and syncope. With evidence to suggest this patient's presentation may be profound reflex syncope in the context of unopposed parasympathetic signalling, consensus was reached to implant a permanent pacemaker. Remarkably, the patient's haemodynamics stabilised and there were no further episodes of syncope.

Definitive aetiology of unexplained syncope after cardiovascular autonomic tests in a tertiary syncope unit.

AIMS: Syncope is a common condition with many possible causes, ranging from benign to life-threatening aetiologies. Establishing a diagnosis can be difficult, and specialized syncope units, using cardiovascular autonomic tests (CATs), including a head-up tilt test, can increase the diagnostic yield. However, up to one-fifth of examined patients have inconclusive CAT results. The aim of the present study was to investigate the predictive value of history, and clinical findings for unexplained syncope after CAT and characterize the group with negative results. METHODS AND RESULTS: Consecutive syncope patients [n = 2663, 61% women, median age 52 (32-69) years] were evaluated and CAT explained aetiology of syncope in 79% of cases, whereas 21% remained unexplained. Predictors of negative CAT were older age at first syncope (+8% higher odds per 10-year increment, P = 0.042), higher supine heart rate (HR; +12% per 10 b.p.m.; P = 0.003), absence of prodromes (+48%; P < 0.001), hypertension (+45%; P = 0.003), diabetes (+82%; P < 0.001), heart failure (+98%; P = 0.014), and coronary artery disease (+51%; P = 0.027). Compared with vasovagal syncope, patients with negative CAT were older, reported more often the absence of prodromes, and had a higher burden of cardiovascular comorbidities. CONCLUSION: A cardiovascular autonomic test established the cause of syncope in 79% of patients evaluated in a syncope unit. Syncope without prodromes and cardiovascular comorbidities were significant predictors of failure to reveal an aetiology from assessment by CAT. These are known risk factors for cardiac syncope and patients with inconclusive CAT warrant further investigation.

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

BACKGROUND AND OBJECTIVES: Vasovagal 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 METHODS: A 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. RESULTS: Seven 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. CONCLUSION: A risk predictive scoring system was successfully developed to identify high-risk VVRs group form PABD patients that performed well.

Pain associated with intravascular instrumentation reduces orthostatic tolerance and predisposes to vasovagal reactions in healthy young adults without needle phobia: a randomised controlled study.

PURPOSE: Vasovagal syncope (VVS), or fainting, is frequently triggered by pain, fear, or emotional distress, especially with blood-injection-injury stimuli. We aimed to examine the impact of intravenous (IV) instrumentation on orthostatic tolerance (OT; fainting susceptibility) in healthy young adults. We hypothesized that pain associated with IV procedures would reduce OT. METHODS: In this randomised, double-blind, placebo-controlled, cross-over study, participants (N = 23; 14 women; age 24.2 ± 4.4 years) underwent head-up tilt with combined lower body negative pressure to presyncope on three separate days: (1) IV cannulation with local anaesthetic cream (EMLA) (IV + EMLA); (2) IV cannulation with placebo cream (IV + Placebo); (3) sham IV cannulation with local anaesthetic cream (Sham + EMLA). Participants rated pain associated with IV procedures on a 1-5 scale. Cardiovascular (finger plethysmography and electrocardiogram; Finometer Pro), and forearm vascular resistance (FVR; brachial Doppler) responses were recorded continuously and non-invasively. RESULTS: Compared to Sham + EMLA (27.8 ± 2.4 min), OT was reduced in IV + Placebo (23.0 ± 2.8 min; p = 0.026), but not in IV + EMLA (26.2 ± 2.2 min; p = 0.185). Pain was increased in IV + Placebo (2.8 ± 0.2) compared to IV + EMLA (2.0 ± 2.2; p = 0.002) and Sham + EMLA (1.1 ± 0.1; p < 0.001). Orthostatic heart rate responses were lower in IV + Placebo (84.4 ± 3.1 bpm) than IV + EMLA (87.3 ± 3.1 bpm; p = 0.007) and Sham + EMLA (87.7 ± 3.1 bpm; p = 0.001). Maximal FVR responses were reduced in IV + Placebo (+ 140.7 ± 19.0%) compared to IV + EMLA (+ 221.2 ± 25.9%; p < 0.001) and Sham + EMLA (+ 190.6 ± 17.0%; p = 0.017). CONCLUSIONS: Pain plays a key role in predisposing to VVS following venipuncture, and our data suggest this effect is mediated through reduced capacity to achieve maximal sympathetic activation during orthostatic stress. Topical anaesthetics, such as EMLA, may reduce the frequency and severity of VVS during procedures requiring needles and intravascular instrumentation.

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

BACKGROUND: Vasovagal 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. METHODS: STRIDES 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. DISCUSSION: The 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 REGISTRATION: ISRCTN: 10412338. Registration date: October 24, 2019.

Recurrent Syncope Episodes during Spinal Anesthesia for Perianal Abscess Drainage: A Case Report Emphasizing Pain as a Trigger.

BACKGROUND Vasovagal syncope is a loss of consciousness caused by decreased arterial pressure and cerebral blood flow. The characteristic features of vasovagal syncope include cardiovascular inhibition caused by neural reflexes, accompanied by vasodilation and bradycardia. To date, there is little literature to report several episodes of syncope under spinal anesthesia during the perioperative period for drainage of an anal abscess. The purpose of this article is to alert clinical practitioners to the early identification of the underlying causes of vasovagal syncope and to facilitate timely and effective management strategies. CASE REPORT We present the case of a 44-year-old man with a perianal abscess who was scheduled for an incision and drainage procedure for the abscess under spinal anesthesia. Preoperative assessment revealed no history of cardiac disease, neurological disorders, or drug allergies. During the perioperative period, the patient experienced 3 episodes of syncope: 1 episode during puncture of spinal anesthesia, and the others at 6.5 h and 8.5 h after the procedure. The patient was discharged 4 days later, and a 30-day postoperative follow-up showed good recovery, without any episodes of syncope. CONCLUSIONS We described a case of 3 episodes of vasovagal syncope occurring in a patient during the perioperative period of drainage of perianal abscess under spinal anesthesia. Pain may have been the main cause of vasovagal syncope in this patient. To avoid vasovagal syncope, it is best for anesthesiologists to choose the lateral position to perform spinal anesthesia and to provide good perioperative pain management for these patients.

A randomized controlled trial of post-donation communication materials to increase donor return following a vasovagal reaction.

BACKGROUND: Vasovagal reactions (VVRs) are one of the primary reasons for people to stop donating blood. The aim of this study was to evaluate the impact of newly developed online communications on the rate of return of whole-blood (WB) and plasma donors who experienced a VVR. STUDY DESIGN AND METHODS: First-time and experienced WB and plasma donors who had a VVR without a loss of consciousness in the previous 3 days were randomly allocated to receive (a) an SMS sent 1-4 days post-VVR (n = 2303), (b) an email sent 6-10 days post-VVR (n = 2360), (c) both the SMS and the email (n = 2248), or (d) business-as-usual donor retention communications (control; n = 2557). Donation data were extracted to determine subsequent donation attempts. RESULTS: For return within 3 months, WB donors in the Email Only condition had significantly increased odds of returning (OR: 1.26, 95%CI: 1.01-1.56). Subgroup analysis within WB donors showed increased odds of return for women sent the SMS and Email (OR: 1.50, 95%CI: 1.14-1.96) or the Email Only (OR: 1.44, 95%CI: 1.10-1.89), and for first-time donors sent the Email Only (OR: 1.48, 95%CI: 1.07-2.05). At 6 months, only first-time WB donors in the Email Only condition had significantly increased odds of returning (OR: 1.30, 95%CI: 1.01-1.69). No significant effects of the intervention were found for immediate or intermediate return for plasma donors. DISCUSSION: Sending an email addressing common donor concerns regarding VVRs increases WB donor retention, but additional strategies are needed for the effects to last and to retain plasma donors.

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

BACKGROUND AND OBJECTIVES: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Association between vitamin D deficiency and vasovagal syncope: A systematic review and meta-analysis.

Vasovagal syncope (VVS) is the most prevalent type of syncope and its management includes pharmacologic and non-pharmacologic interventions. Recently, studies have investigated vitamin D levels in VVS patients. In this systematic review and meta-analysis, we aim to review these studies to find possible associations between vitamin D deficiency and vitamin D levels with VVS. International databases including Scopus, Web of Science, PubMed, and Embase were searched with keywords related to "vasovagal syncope" and "vitamin D." Studies were screened and the data were extracted from them. Random-effect meta-analysis was conducted to calculate the standardized mean difference (SMD) and 95% confidence interval (CI) for vitamin D levels in comparison to VVS patients and controls. Also, VVS occurrence was measured and the odds ratio (OR) and 95% CI were calculated for comparison of vitamin D deficient cases and nondeficient individuals. Six studies were included with 954 cases investigated. Meta-analysis showed that patients with VVS had significantly lower vitamin D serum levels in comparison to non-VVS cases (SMD -1.05, 95% CI -1.54 to -0.57, p-value < .01). Moreover, VVS occurrence was higher in vitamin D-deficient individuals (OR 5.43, 95% CI 2.40 to 12.27, p-value < .01). Our findings which show lower vitamin D levels in VVS patients can have clinical implications in order for clinicians to pay attention to this when approaching VVS. Further randomized controlled trials are certainly warranted to assess the role of vitamin D supplementation in individuals with VVS.

Vasovagal syncope: An overview of pathophysiological mechanisms.

Syncope is a short-term transient loss of consciousness, characterized by rapid onset and complete spontaneous recovery. According to the 2018 European Society of Cardiology guidelines, three different types of syncope have been identified. However, all forms of syncope share a common final pathophysiological event, global cerebral hypoperfusion, which results from the inability of the circulatory system to maintain blood pressure at the level required to efficiently supply blood to the brain. The vasovagal syncope (VVS) is the most common form of syncope. Although, VVS is generally harmless, its frequent occurrence can negatively affect quality of life and increase the risk of adverse events. The pathophysiological mechanisms underlying VVS remain obscure. The multifaceted nature of VVS presents a veritable challenge to understanding this condition and developing preventative strategies. Thus, the aim of this review was to discuss the factors contributing to the pathogenesis of VVS and provide guidance for future research.

Vasovagal Syncope at Work: A Narrative Review for an Occupational Management Proposal.

Syncope is a complex clinical manifestation that presents considerable diagnostic difficulties and, consequently, numerous critical issues regarding fitness for work, especially for high-risk tasks. To date, it is impossible to quantify the exact impact of syncope on work and public safety since it is highly improbable to identify loss of consciousness as the fundamental cause of work or driving-related accidents, especially fatal injuries. Working at high-risk jobs such as public transport operators, in high elevations, or with exposure to moving parts, construction equipment, fireworks, or explosives demand attention and total awareness. Currently, no validated criteria or indicators are available for occupational risk stratification of a patient with reflex syncope to return to work. By drawing inspiration from the updated literature, this narrative review intends to summarise the leading knowledge required regarding the return to work for subjects affected by syncope. According to the available data, the authors highlighted some key findings, summarised in macro-items, such as defined risk stratification for vasovagal accidents, return to work after a critical event, and a focus on pacemaker (PM) implementation. Lastly, the authors proposed a flowchart for occupational physicians to help them manage the cases of workers affected by syncope and exposed to levels of risk that could represent a danger to the workers' health.

Lidocaine Tape Application for 3 Hours Prevents Vasovagal Syncope During Venipuncture: A Case Series.

Vasovagal syncope (VVS) or reflex is usually caused by physical and mental stress-related factors, like pain, anxiety, and fear, and it is one of the most frequent complications during dental treatment. Two patients, both with histories of dental phobia and of VVS during vaccination, venipuncture, and dental treatment with local anesthetics, were scheduled for dental treatment under intravenous (IV) sedation. However, both experienced episodes of VVS that occurred during venipuncture using a 24-gauge indwelling needle. We determined that pain was the main trigger of VVS for these patients and attempted to reduce venipuncture-associated pain using 60% lidocaine tape applied 3 hours before venipuncture at their next dental visits, respectively. Use of the lidocaine tape was successful and permitted comfortable placement of the IV catheter without any onset of VVS.

[Risk factors associated with malignant vasovagal syncope in children].

Objective: To analyze the clinical characteristics and risk factors of malignant vasovagal syncope (VVS) in children. Methods: This was a case-control study. The data of 368 VVS patients who were treated in the Department of Cardiology, Children's Hospital, Capital Institute of Pediatrics from June 2017 to December 2021 was collected and analyzed. They were divided into malignant VVS group and non-malignant VVS group according to the presence of sinus arrest, and then their demographic characteristics were compared. The children with malignant VVS and complete clinical information were recruited into the case group and were matched by age and sex (1∶4 ratio) with non-malignant VVS patients during the same period.Their clinical characteristics and lab tests were compared. Independent sample t test, Mann Whitney U or χ2 test was used for comparison between groups.Logistic regression was used to analyze the risk factors for malignant VVS in children. Results: Eleven malignant VVS and 342 non-malignant VVS met the inclusion and exclusion critera. Eleven malignant VVS and 44 non-malignant children were recruited in the case-control study. Ten patients of the 11 malignant VVS had a cardiac arrest occurring at 35 (28, 35) minutes of the head-up tilt test, and the duration of sinus arrest was (9±5) s. One patient had syncope occurring while waiting for drawing blood, and the duration of sinus arrest was 3.4 s. The children with malignant vasovagal syncope were younger than non-malignant VVS patients (9 (7, 10) vs. 12 (10, 14) years old, P<0.05), and had higher mean corpuscular hemoglobin concentration (MCHC) and standard deviation of the mean cardiac cycle over 5-minute period within 24 hours ((347±9) vs. (340±8) g/L, (124±9) vs. (113±28) ms, both P<0.05). Logistic regression analysis showed that MCHC was an independent risk factor for malignant VVS in pediatric patients (OR=1.13, 95%CI 1.02-1.26, P=0.024). Conclusions: The onset age of malignant VVS was younger, with no other special clinical manifestations. MCHC was an independent risk factor for malignant VVS.

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 450 ml 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.