Vasovagal syncope, a common cause of fainting, is generally not dangerous but can lead to injuries from falls and be particularly hazardous if it occurs while driving. It is a reflex syncope and the most common cause of fainting, affecting many children and young adults. This article explores vasovagal syncope, its diagnosis, treatment, and the role of dietary interventions, particularly increased salt and water intake, in managing the condition.
Understanding Vasovagal Syncope
Vasovagal syncope is a reflex reaction to triggers such as needles, seeing blood, stress, anxiety, emotional upset, fatigue, or exhaustion. This reaction starts in the autonomic nervous system, particularly involving the vagus nerve, which controls heart rate and blood pressure. When the vagus nerve becomes overactive, it can cause heart rate and blood pressure to drop too much or too quickly. This leads to insufficient blood flow to the brain, resulting in a loss of consciousness.
Symptoms
Symptoms often manifest 30 to 60 seconds before a vasovagal syncopal episode. Common symptoms include:
- A sudden feeling of tiredness (fatigue)
- A sudden warm feeling
- Lightheadedness or dizziness
- Loss of color in your skin (pallor)
- Nausea
- Profuse sweating
- Slow pulse
- Yawning
- Tunnel vision
During an episode, individuals may experience brief disorientation or confusion, eyes staying open but rolling up and back into the head, falling, loss of bladder control, and twitching movements. Recovery usually occurs within 20 to 30 seconds after regaining consciousness, though some people may feel nauseous or fatigued for a short time.
Diagnosis of Vasovagal Syncope
Diagnosing vasovagal syncope typically begins with a healthcare professional reviewing your medical history and performing a physical exam. The physical exam includes listening to your heart and taking your blood pressure while lying down, seated, and then standing. In many children and young adults, this may be all that is needed. However, the healthcare provider may recommend several tests to rule out other possible causes for fainting, particularly dangerous heart-related conditions.
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Diagnostic Tests
- Electrocardiogram (ECG): This test records the electrical signals your heart produces to detect irregular heart rhythms and other cardiac conditions.
- Echocardiogram: An ultrasound of the heart to assess its structure and function.
- Exercise Stress Test: This test studies heart rhythms during exercise to identify any abnormalities.
- Blood Tests: To rule out other potential causes of fainting.
- Tilt Table Test: If no heart conditions appear to be the cause, a tilt table test may be recommended. During this test, you lie flat on your back on a table that changes positions, tilting you upward at various angles to monitor for a fainting response.
Treatment and Management Strategies
In many cases of vasovagal syncope, specific medical treatment is unnecessary. The primary goal is to prevent fainting episodes.
Lifestyle Adjustments and Therapies
- Physical Counterpressure Maneuvers: If you recognize the warning signs of vasovagal syncope, like dizziness, nausea, or sweaty palms, lie down right away. If lying down isn't possible, sitting down and putting your head between your knees can help. Tensing your leg muscles, clenching your fists, or crossing your legs can also help prevent fainting by increasing blood pressure.
- Orthostatic Training: Healthcare providers sometimes recommend orthostatic training to gradually increase the amount of time spent upright, helping the body adjust to changes in position and blood pressure.
- Compression Stockings: Wearing compression stockings can lessen the pooling of blood in your legs.
- Foot Exercises: Regular foot exercises can also help improve blood circulation.
Pharmacological Interventions
- Medicines: A drug called fludrocortisone acetate, usually used to treat low blood pressure, may be helpful in preventing vasovagal syncope in some individuals. However, the benefits may be uncertain.
Dietary Recommendations: The Role of Salt and Water Intake
Increasing salt and water intake is a therapeutic measure reported for children with VVS, achieving therapeutic effects against the supposed pathogenesis. In theory, increased salt and water intake not only directly increases plasma volume but can also influence the regulation of cerebral and peripheral blood vessels during standing, which may improve tolerance to orthostatic challenge. It was also suggested that increased salt and water intake may reduce sympathetic activity during orthostatic stress, which was considered to trigger the Bezold-Jarisch reflex leading to syncope in patients with VVS. In addition, it is more acceptable to increase salt and water intake than to take medicines regarding the advantages of easy implementation, mild adverse reactions, and the relatively benign prognosis of VVS, especially for pediatric patients.
Meta-Analysis of Salt and Water Intake Studies
A meta-analysis was conducted to evaluate the efficacy of increased salt and water intake in treating pediatric VVS. The databases searched included Cochrane Library, EMBASE, PubMed, Web of Science, VIP, Wanfang, and China National Knowledge Infrastructure (CNKI). The search terms (in English or Chinese) were “vasovagal syncope,” “reflex syncope,” “salt,” “sodium chloride,” “oral rehydration salts,” “hydration and salt,” “drinking water,” “saline solution,” “saline waters,” and “conventional therapy.”
The analysis included five randomized controlled trials (RCTs), comprising 233 children in the salt and water intervention group and 179 in the control group, who received non-medicinal conventional therapy. The results indicated that the negative changing rate of the head-up tilt test (HUTT) in the intervention group (144/233, 61.8%) was significantly higher than in the control group (48/179, 26.8%) (P < 0.00001).
Key Findings
- HUTT Response: The meta-analysis revealed that the HUTT negative changing rate in the intervention group was remarkably higher than that in the control group (RR: 2.29, 95% CI: 1.75-2.99, P < 0.00001).
- Recurrence Rate: The syncope or presyncope recurrence rate in the intervention group was significantly lower than in the control group (RR: 0.72, 95% CI: 0.58-0.88, P = 0.002).
Practical Implementation
In the included studies, patients in the intervention group were asked to take 500 milliliters (ml) of water (standard oral rehydration salts solution) orally as a supplement in addition to daily water intake. The supplementary quantity of salt varied across studies, with some providing 14.75 grams (g) of salt (containing sodium chloride 1.75 g) per day and others providing 5.125 g of salt (containing sodium chloride 0.65 g) per day.
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Subgroup Analysis
A subgroup analysis was conducted based on whether upright training was part of the treatment. The results showed that:
- Without upright training, the negative changing rate of the HUTT in the intervention group was higher than in the control group (RR: 2.50, 95% CI: 1.32-4.75, P = 0.005), but there was no difference in the recurrence rate of syncope or presyncope.
- With upright training, the negative changing rate of the HUTT in the intervention group was higher than in the control group (RR: 2.24, 95% CI: 1.67-3.00, P = 0.000), and the recurrence rate of syncope or presyncope in the intervention group was lower than in the control group (RR: 0.69, 95% CI: 0.55-0.88, P = 0.003).
Considerations and Limitations
Despite the benefits of increased salt and water intake, the negative changing rate of HUTT and symptom-free rate were not very high. Several factors may affect the outcomes of oral rehydration salts (ORS) therapy, including:
- Baseline symptom severity
- Amount of salt and water supplement
- Influence of daily diet
- Hemodynamic type of VVS
- Patient compliance
Safety and Adverse Reactions
Three studies mentioned adverse reactions in children treated with increased salt and water intake, and no relevant adverse reactions were reported.
When to Seek Medical Advice
While vasovagal syncope is generally not dangerous, it is essential to consult a healthcare provider to rule out other potential causes of fainting, particularly if you have heart-related concerns. Additionally, seek medical advice if you experience frequent or severe episodes of fainting, especially if you don’t usually have warning signs before you faint. If your vasovagal syncope is not under control, your healthcare provider may advise against driving or other activities that could be dangerous.
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