Syncope is the transient, self-limited, loss of consciousness (fainting) caused by decreased blood flow to the brain followed by spontaneous recovery.
The term syncope excludes seizures, coma, shock, or other states of altered consciousness.
According to the Cleveland Clinic, it often results from a sudden decrease in blood pressure, blood volume changes or a lowered heart rate.
In addition to hypotension (low blood pressure), medical conditions such as anemia, metabolic or autonomic nervous system abnormalities and circulation and heart problems can cause syncope. Although syncope can occur in people with no abnormalities, it is important to determine its cause to rule out serious medical conditions.
Although most causes of syncope are benign (harmless), this symptom presages a life-threatening event in a small subset of patients.
Syncope occurs due to global cerebral hypoperfusion (decrease blood supply). Brain parenchyma depends on adequate blood flow to provide a constant supply of glucose, the primary metabolic substrate. Brain tissue cannot store energy in the form of high-energy phosphates found elsewhere in the body; therefore, a cessation of cerebral perfusion lasting only 3-5 seconds can result in syncope.
Hypotension, or low blood pressure, is a common cause of syncope. Fainting occurs when the person changes position by standing or sitting, causing blood to pool in the lower extremities (below the diaphragm). In addition to fainting during a hot shower, susceptible individuals may experience syncope when sitting for long periods of time, after exercise and after eating a large meal.
Causes of Fainting During Hot Showers:
During a hot shower, the body tries to cool itself by dilating its blood vessels. This results in less blood flow to the brain, resulting in light-headedness, dizziness and syncope. The elderly are more susceptible to syncope, because their blood vessels are less elastic. Therefore, they are more likely to faint when their blood pressure drops or when their blood circulation changes. In addition, factors such as hypoglycemia (low blood sugar) or dehydration will make individuals more susceptible to fainting during a hot shower.
Tips for Taking Hot Showers:
Prevent steam from building up in the shower by opening a bathroom window or door. Limit time spent in hot showers to five minutes; or, if taking long showers, come out of the shower every five minutes. Lying flat on the floor or with the legs slightly elevated if you feel faint promotes blood flow back to the head.
Other conditions can mimic syncope. A CNS event, such as a hemorrhage or an unwitnessed seizure, can present as syncope. Syncope can occur without reduction in cerebral blood flow in patients who have severe metabolic derangements (eg, hypoglycemia, hyponatremia, hypoxemia, hypercarbia).
Currently, no specific testing has sufficient power to be absolutely indicated for evaluation of syncope. Research-based and consensus guideline recommendations are listed below.
Serum glucose level
In one study, 2 of 170 patients with syncope tested for serum glucose were found to be hypoglycemic.
Despite this low yield, rapid blood glucose assessment is easy, fast, and may be diagnostic, leading to efficient intervention.
If performed empirically, a CBC count has an exceedingly low yield in syncope. Some risk stratification protocols use a low hematocrit level as a poor prognostic indicator.
A prospective evaluation of syncope found that 4 of 170 patients had signs and symptoms of GI hemorrhage with a confirmatory CBC count. No occult bleeding was diagnosed based on an empiric CBC count in this study.
Anemia has been shown in several studies to suggest poor short-term outcomes.
Serum electrolyte levels with renal function
These tests if performed empirically have an exceedingly low yield in syncope. Some risk stratification protocols use electrolyte level abnormalities and renal insufficiency as poor prognostic indicators.
In the study by Martin et al, 134 patients with syncope had electrolytes drawn as part of the routine workup. One patient was unexpectedly found to be hyponatremic secondary to diuretic use.
Serum electrolyte tests are indicated in patients with altered mental status or in patients in whom seizure is being considered.
If arrhythmia is noted, evaluation of electrolytes may be useful.
These tests are indicated in patients who give a history of chest pain with syncope, dyspnea with syncope, or exertional syncope; those with multiple cardiac risk factors; and those in whom a cardiac origin is highly suspected.
Total creatine kinase (CK)
A rise in CK levels may be associated with prolonged seizure activity or muscle damage secondary to a prolonged period of loss of consciousness.
BNP level >300 pg/mL is a predictor of serious outcomes at 30 days.
In elderly and debilitated patients, UTI is common, easily diagnosed, and treatable and may precipitate syncope. UTIs may occur in the absence of fever, leukocytosis, and symptoms in this population.
A Patient who presents with syncope should be throughly evaluated. The most important part is the history of the syncope along with the associated risk factors, specially any history of any cardiovascular disease.
The test which may require depending on patient's history and examination can vary from very basic tests to more sophisticated work up which may include:
Holter monitor/loop event recorder
Head-up tilt-table test
CT Chest and Abdomen
Emergency Department Care:
In patients brought to the ED with a presumptive diagnosis of syncope, appropriate initial interventions include intravenous access, oxygen administration, and cardiac monitoring. ECG and rapid blood glucose evaluation should be promptly performed. A study to determine the sensitivity and specificity of the San Francisco Syncope Rule (SFSR) ECG criteria for determining cardiac outcomes found that when used correctly, the criteria can help predict which syncope patients are at risk of cardiac outcomes. ECG criteria predicted 36 of 42 patients with cardiac outcomes, with a sensitivity of 86%, a specificity of 70%, and a negative predictive value of 99%.
Syncope may be the manifestation of an acute life-threatening process but is generally not emergent. Clinically ruling out certain processes is important. The treatment choice for syncope depends on the cause or precipitant of the syncope. Patients in whom a cause cannot be ascertained in the ED, especially if they have experienced significant trauma, warrant supportive care and monitoring.
Situational syncope treatment focuses on educating patients about the condition. For example, in carotid sinus syncope, patients should be instructed not to wear tight collars, to use a razor rather than electric shaver, and to maintain good hydration status; they should also be informed of the possibility of pacemaker placement in the future.
Orthostatic syncope treatment also focuses on educating the patient. Inform patients about avoiding postprandial dips in BP, teach them to elevate the head of their bed to prevent rapid BP fluctuations on arising from bed, and emphasize the importance of assuming an upright posture slowly. Additional therapy may include thromboembolic disease (TED) stockings, mineralocorticoids (eg, fludrocortisone for volume expansion), and other drugs such as midodrine (an alpha1-agonist with vasopressor activity). Patients' medications must be reviewed carefully to eliminate drugs associated with hypotension. Intentional oral fluid consumption is useful in decreasing frequency and severity of symptoms in these patients.
Cardiac arrhythmic syncope is treated with antiarrhythmic drugs or pacemaker placement. Consider cardiologist evaluation or inpatient management since this is more commonly associated with poor outcomes. Trials assessing beta-blockade to prevent syncope have conflicting results, but no clear effect has been demonstrated.
Cardiac mechanical syncope may be treated with beta-blockade to decrease outflow obstruction and myocardial workload. Valvular disease may require surgical correction. This, too, is associated with increased future morbidity and mortality.
According to the cause of Syncope.