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Syncope? Consider a Benign Cause First

Roberts, James R. MD

doi: 10.1097/01.EEM.0000574812.55119.6d



Syncope is an everyday complaint in the ED, and emergency clinicians are tasked with attempting to find its cause, initiating immediately needed treatment, and providing appropriate follow-up. The causes of syncope run the gamut from life-threatening to benign, and the actual cause often cannot be determined.

It is not uncommon on a hot Sunday afternoon to see a patient who passed out in church with no obvious cause and who is now completely back to normal. A standard history and physical are often unrevealing in such a situation, and a variety of tests fail to determine the etiology. This is most likely a benign syncopal event, but the next best steps are often difficult to define, and hospital admission and a plethora of other tests are often initiated.

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Micturition Syncope: A Reappraisal

Kapoor WN, Peterson JR, Karpf M



The diagnosis of micturition syncope depends entirely on the history. It is a benign condition, and a basic ED evaluation is required. These authors described syncope as a sudden transient loss of consciousness associated with the inability to maintain postural tone that is not compatible with seizure, vertigo, dizziness, coma, shock, or other states of altered consciousness. Micturition syncope was originally described in 1959. (New Engl J Med. 1959;260[7]:328.)

Micturition syncope occurs at the beginning, during, termination, or immediately after urination. It was originally described in healthy young men who experienced it after rising in the morning. Individuals experience sudden loss of consciousness, but recovery is rapid and recurrences rare. Predisposing factors include reduced food intake, fatigue, and ingestion of alcohol. The actual mechanism of syncope is unknown, but it is probably mediated by vagal tone. These authors said their report of 33 patients essentially redefines the spectrum of micturition syncope.

Patients with syncope were evaluated with a history, a clinical exam, baseline laboratory evaluations, and a 12-lead ECG. These patients had 24 hours of prolonged EEG monitoring, but that test rarely provided significant clinical information. A head CT scan was not considered essential in evaluating these patients.

Eight of the 33 patients were young, previously healthy men with a mean age of 25 who had a syncopal episode with micturition in the early evening hours or when awakened from sleep at night. Only one patient had more than one episode. This subgroup has been described previously. All of the investigations in this subgroup were normal, and the diagnosis was considered secondary to urination.

The other 25 patients were older, with a mean age of 60, and had multiple medical problems. Most were women, and many were taking several medications (3.5 per patient). The underlying medical conditions included hypertension, congestive heart failure, diabetes, and cerebral vascular disease. Examination disclosed that 22 of 25 patients had orthostatic hypotension. Most patients had a single episode, but one patient had more than 100 episodes of syncope with micturition. Most were recumbent prior to the syncope. Most patients passed out at termination or just after the end of micturition. Laboratory tests and ECG and EEG monitoring failed to reveal any specific diagnostic causes, even in patients with multiple medical problems. Therapy was primarily aimed at improving orthostasis.

Follow-up was available on all patients for about 15 months, with no recurrence of micturition syncope or sudden death. The patient who had 100 previous episodes had no more episodes after diuretics were stopped.

These authors said their study further defined the incidence of micturition syncope to include many older patients with underlying medical problems. The exact mechanism of micturition syncope could not be clarified, but the authors noted that the majority of older patients had orthostatic hypotension. The contribution of orthostatic hypotension was also unclear.

Comment: Micturition syncope is a type of reflex syncope, essentially consisting of vasodilation and bradycardia, systemic hypotension, and decreased cerebral profusion. The most common cause is vasovagal syncope, but the exact diagnosis often cannot be ascertained. The differential diagnosis of syncope is gargantuan, and the history is most important because micturition syncope can be identified if the patient passed out during or shortly after urination. Patients will often have a few seconds of myoclonic jerks that simulate a seizure, but they will wake up and be normal in a short time. Patients often complain of lightheadedness, sweating, or blurred vision just prior to the syncope.

The ED evaluation of a syncopal episode is relatively standard and includes a history and physical examination, basic laboratory tests, and an ECG. All tests will be negative if the history clearly defines syncope during micturition. Unfortunately, no therapy has been proven to help with vasovagal syncope, although patients should be reassured that it's benign and warned about potential injury from a fall. They should avoid prolonged standing, straining during micturition, and stressful situations. They should also lie flat when they feel symptoms coming on.

EPs should consider altering medications that may predispose syncope. Diuretics appear to be a common cause, and these medications can be often temporarily stopped. Other similar causes of syncope are coughing and defecation, occurring more commonly in elderly women.

Hospitalization is not required for patients who have a firm diagnosis of micturition or defecation syncope. Curiously, it usually does not recur, and a few interventions can prevent it. (See table.) The key is ruling out an underlying cause. Orthostatic hypotension is one of the culprits.

These authors stated that a head CT scan is not required in patients with syncope, but my experience is that patients will not be admitted to the hospital for syncope without one, though I cannot think of a single patient with syncope in whom a head CT was helpful. One of the main issues in the ED is differentiating syncope from a seizure, noting that brief seizure activity after benign syncope is not uncommon. A few hours of observation is prudent after tests are normal in the elderly who have underlying medical conditions and are taking medications.

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Factors that May Play a Role in Micturition Syncope

  • Alcohol
  • Hunger
  • Fatigue
  • Dehydration
  • Medical conditions, such as a respiratory infection
  • Use of alpha blockers to improve urination in men with prostate problems
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Strategies to Prevent Micturition Syncope

  • Avoid excessive alcohol consumption.
  • Don't get out of bed suddenly. Advise patients to sit on the edge of the bed and move their legs, making sure they aren't dizzy or lightheaded.
  • Urinate sitting down.
  • Consider that medications may be causing the condition.

Reader Feedback: Readers are invited to ask specific questions and offer personal experiences, comments, or observations on InFocus topics. Literature references are appreciated. Pertinent responses will be published in a future issue. Please send comments to

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Dr. Robertsis a professor of emergency medicine and toxicology at the Drexel University College of Medicine in Philadelphia. Read the Procedural Pause, a blog by Dr. Roberts and his daughter, Martha Roberts, ACNP, PNP, at, and read his past columns at

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