What is the cause of syncopal (loss of consciousness due to transient lack of cerebral blood flow) fainting?

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From the Guidelines

If you experience syncopal fainting, or syncope, sit or lie down immediately when feeling lightheaded to prevent falls and injuries, as this is the most effective way to manage the condition and prevent further complications 1.

Causes and Management of Syncope

Syncopal fainting, or syncope, is a temporary loss of consciousness caused by insufficient blood flow to the brain. Common causes include dehydration, sudden position changes, emotional stress, prolonged standing, and certain medications. To manage syncope, it is essential to:

  • Stay well-hydrated by drinking 6-8 glasses of water daily
  • Change positions slowly (especially when getting up from lying down)
  • Avoid prolonged standing
  • Recognize trigger situations If you have recurrent episodes, keeping a diary noting circumstances surrounding each event can be helpful in identifying patterns and triggers.

Importance of Medical Evaluation

Medical evaluation is essential for recurring syncope, as it may indicate underlying heart conditions like arrhythmias or structural abnormalities. Treatment depends on the cause and may include medication adjustments, compression stockings to improve blood return from the legs, or specific medications to regulate blood pressure or heart rhythm. According to the 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope, a thorough history, physical examination, and ECG are crucial in determining the underlying cause of syncope 1.

Physical Counterpressure Maneuvers (PCMs)

The 2019 American Heart Association and American Red Cross focused update for first aid recommends the use of PCMs, such as handgrip, arm tensing, abdominal muscle tensing, leg crossing with tensing, squatting, and neck flexion, to prevent syncope in individuals experiencing presyncope 1. These maneuvers can help increase blood pressure, improve symptoms, and prevent syncope. However, it is essential to note that PCMs are not recommended when symptoms of a heart attack or stroke accompany presyncope.

Prevention and Treatment

Syncope occurs because of a temporary drop in blood pressure or heart rate, reducing cerebral blood flow below the level needed for consciousness, with most episodes resolving quickly as blood flow normalizes when in a horizontal position. By recognizing the signs and symptoms of presyncope, such as pallor, sweating, lightheadedness, visual changes, and weakness, individuals can take prompt action to prevent syncope and reduce the risk of injury.

From the Research

Definition and Prevalence of Syncopal Fainting

  • Syncopal fainting, also known as vasovagal syncope, is a common disorder that affects at least 20% of people at some time in their lives 2.
  • It is characterized by an abrupt loss of consciousness in response to reduced perfusion to the brain, resulting from a complex neurologic reflex 3.

Diagnostic Approaches and Prognostic Understanding

  • The last 15 years have seen striking advances in diagnostic approaches and prognostic understanding of vasovagal syncope 2.
  • Head-up tilt testing is a clinical test used to reproduce reflex syncope, but its diagnostic yield has been recently redefined 4.

Treatment Options

  • Various physiological, pharmacological, and electrical therapies have been developed and tested to manage vasovagal syncope, including:
    • Counterpressure manoeuvres
    • Salt and fluid recommendations
    • Fludrocortisone
    • Midodrine
    • Beta-blockers
    • Serotonin reuptake inhibitors
    • Permanent pacemakers 2, 3, 4
  • Midodrine has been shown to be effective in preventing vasovagal syncope recurrences, particularly in patients who are refractory to beta-blockers 5, 6.
  • A two-step therapeutic strategy, with metoprolol as first-line treatment and midodrine as second-line treatment, has been proposed for patients with neurocardiogenic syncope 5.

Efficacy of Midodrine

  • A randomized clinical trial found that midodrine can reduce the recurrence of syncope in healthy, younger patients with a high syncope burden 6.
  • The study found that fewer patients receiving midodrine had at least one syncope episode during follow-up, with a relative risk of 0.69 (95% CI, 0.49 to 0.97; P = 0.035) 6.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Management of vasovagal syncope: 2004.

Expert review of cardiovascular therapy, 2004

Research

Vasovagal syncope: an update on the latest pharmacological therapies.

Expert opinion on pharmacotherapy, 2015

Research

Novel Therapeutic Options in the Management of Reflex Syncope.

American journal of therapeutics, 2019

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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