Beyond the Basics: Syncope

     This CE activity is approved by EMS Magazine, an organization accredited by the Continuing Education Coordinating Board for Emergency Medical Services (CECBEMS), for 1.5 CEUs.

• Discuss the pathophysiology of syncope
• Review prehospital assessment and management of the syncope patient

     Whether in the hospital or prehospital environment, syncope is one of the more perplexing diagnostic challenges facing clinicians. An understanding of the pathophysiology behind syncope, common causes and diagnostically significant examination items can lead to appropriate field decisions and treatment.

     You are called to a 67-year-old man who has fallen from a small stepladder. His coworker tells you that he seemed unresponsive after the fall for "a few minutes." Upon your arrival, the patient is alert and oriented, and is refusing care. He doesn't believe he slipped or tripped. "I think I just passed out for a minute," he says. "It happens."

     The above is a classic presentation of syncope, which is defined as a transient, self-correcting loss of responsiveness and postural tone. In the simplest terms, the patient passes out, falls down and quickly returns to normal. Depending on the patient's position when syncope occurs, injury may occur. If the patient is still unresponsive upon your arrival or has a lingering altered mental status, he has not experienced syncope.

     Syncope is not a disease in itself, but rather a term for the physical presentation that occurs when the brain, which is particularly sensitive to deprivation of oxygen and glucose, is deprived of circulation.

     The brain, which at any given time consumes about 20% of the body's oxygen, does not tolerate anaerobic metabolism as well as other parts of the body. Without oxygen and glucose, brain function rapidly ceases. A loss of approximately 35% of cerebral blood flow will result in unresponsiveness. Both the cerebrum and the reticular activating system have roles in consciousness and posture; hypoperfusion to both areas results in syncope.

     There are many potential causes of syncope. This section breaks down the more common causes into pathophysiology-based sections.

     Vascular and blood-related causes: Low volume may result from a wide range of conditions including gastrointestinal bleeding, vomiting or diarrhea. Diminished oral intake and excessive heat with perspiration can worsen the condition. A history or indication of anemia, cancer, sepsis or other shock condition may also cause a syncopal episode. The vascular system is usually involved to some degree in all cases of syncope.

     Cardiac causes include arrhythmia and myocardial infarction. Obstruction of blood from the heart (outflow obstruction) may be caused by valvular problems such as stenosis of the aortic, pulmonic or mitral valves. Obstruction may also be caused by pulmonary embolus or pericardial tamponade. Patients who experience syncope during exertion are more likely to have an outflow obstruction.

     The most common metabolic cause of syncope is hyperventilation. Hypocapnia (low carbon dioxide) causes cerebral vasoconstriction, resulting in cerebral hypoperfusion and syncope. Diabetic conditions may also cause syncope. Hypovolemia secondary to the osmotic diuresis seen in hyperglycemia is possible. Hypoglycemia is frequently responsible for altered mental status and sometimes syncope, but extremely low blood glucose levels are not self-correcting and would generally not present as syncope.

     Neurologic causes: Many neurological diseases can be a cause or contributing factor to syncope. Patients with Parkinson's disease and Guillain-Barre may be more prone to syncope, and more extensive diabetic neuropathies may also be an etiology or contributing etiology.

     Vasovagal and vasoactive causes can also fit into or interact with the categories listed above. These include:

• Alcohol ingestion (by vasodilaton)
• Bowel movements or micturition (urination), especially when constipated or urinating against an obstruction
• Stress, heat, standing with knees locked, crowds
• Carotid sinus stimulation (shirt collar, rapid movement of the head).

     Your first contact with the syncope patient—or any patient—should focus on the primary assessment. Take spinal precautions, if necessary, and manage the ABCs. In true syncope cases, the patient will not require ventilation or resuscitation. If the patient continues to have an altered mental status or requires resuscitation, he is not experiencing syncope.

     Oxygen administration via non-rebreather or nasal cannula should be performed based on patient presentation and oxygen saturation readings. Note important circulatory signs during this phase, including skin color, temperature and condition, and take a quick pulse check for unusual bradycardia or tachycardia.

     In the overall approach, assessment and care for potentially life-threatening conditions (e.g., arrhythmia) should be performed early in the process, especially when signs point to these conditions.

     The differential diagnostic process for syncope involves a wide range of pathologies (see Table I) and a series of conditions that mimic syncope but should be differentiated (Table II). Since syncope is a medical presentation, the patient history is usually the source of the greatest and most relevant information. In syncope, a detailed history of events surrounding the incident is vital.

     While patients may tell you they were "going to the bathroom" when they lost consciousness, the exact details should be explored. It may mean anything from rising from a chair and walking to the bathroom to urinating or defecating—all of which could be implicated in syncope. Furthermore, the exact details of prodromes leading up to the incident, the duration of unresponsiveness and any activity during this period are equally noteworthy. Patients may report blacking or whiting out prior to loss of consciousness. Family and bystanders may report periods of staring into space or seizure activity (focal or tonic-clonic) as part of the episode.

     The history should follow the SAMPLE mnemonic. Attention to the events can yield significant results. Ask the patient:

• Did you have any unusual sensations prior to the event (whiting or blacking out, feeling faint or dizzy, cool, clammy skin, etc.)?
• Did you experience rapid, bounding or irregular heartbeat?
• Did you experience pain or other unusual sensations?
• Have you experienced any signs of bleeding (including hematochezia, melena or hematemesis)?
• Ask about risk factors such as hypertension, hypercholesterolemia, diabetes, etc., which may indicate a higher probability of underlying serious causes of syncope.

     You may have to rephrase questions to get the maximum diagnostic benefit. Asking, "Did you have any warning you were going to pass out?" may evoke an important recollection from just prior to the incident.

     Simple differentiation between sudden and gradual onset also has diagnostic value in the syncope patient. Arrhythmic causes are usually sudden in onset, while symptoms of sepsis and gastrointestinal bleeding may have been present in some form for days.

     Other portions of the SAMPLE history, such as medications and oral intake, provide vital clues to potential causes of syncope.

     Observe the surroundings for temperature and other environmental factors. Ask family members and bystanders for their observations of seizure activity, potential for injury and the period of unresponsiveness, but remember that their observations may be subjective and tempered by emotion or excitement.

     Your physical examination order and priorities will be based on findings from the history. First, examine areas that seem likely or may pose the greatest life threat (e.g. cardiac work-up in response to report of palpitations or suspected myocardial infarction).

     The physical exam is another way to rule out potential causes of syncope or conditions that mimic syncope, using causes of altered mental status as a guide.

     Orthostatic hypotension is a relatively reliable sign of hypovolemia when evaluated properly. Evaluation involves measuring the pulse and blood pressure of the patient in a recumbent position and comparing it against the same vitals while he is standing.

     In an ideal situation, the patient should be recumbent for 10 minutes before being moved to a standing position. Measure vitals immediately, then at 30 seconds and at two minutes. It is rare to meet each of these criteria in the field, as doing so may delay transportation and not be of value for the information returned.

     In a more general application of orthostatic vital signs (also called a tilt test), you will find the patient in a sitting or recumbent position. Take whatever time you would to obtain a history before obtaining baseline vitals. Take the vitals while the patient is sitting or recumbent; however, if spinal injury is suspected, do not perform this test.

     As the patient stands, observe him carefully. If the sudden change in position causes syncope, be prepared to bring him safely to a recumbent position. This is actually a diagnostic sign in itself. If the patient becomes dizzy or weak, or develops an altered mental status upon standing, he is considered to have a positive test—especially if he recovers when placed in the recumbent position. Stop the test immediately.

     When the patient stands, look for other signs of shock, including changes in skin color, temperature and condition. A pulse increase of greater than 20 beats per minute or a blood pressure decrease of 10–20 mmHg systolic reflects a positive tilt test. Remember to look at the overall patient picture and limits in field application of this test.

     Below are general rules to consider when evaluating causes of syncope:

• If the patient is active immediately prior to the syncopal episode, consider obstructive causes.
• If the patient is recumbent or supine when syncope occurs, consider arrhythmic causes.
• If the patient is standing (but not exerting), consider vasovagal causes.

     The overall patient picture is important because of variables such as false positives in the tilt test (seen in geriatric patients) or false negatives (medications that prevent compensatory increases in pulse even though hypovolemia is present).

     Depending on the patient presentation and history you may choose to use the following tests in your physical examination:

• Stroke scale
• Blood glucose monitoring
• 12-lead EKG
• Orthostatic blood pressure.

     The true syncope patient will have few remaining symptoms and may wish to refuse care and transportation. Although the cause of syncope isn't diagnosed in more than half of the patients seen in emergency departments, the potential for syncope to occur again after EMS leaves makes it worthwhile to convince them to accept transportation.

     Patients with more serious underlying conditions, such as suspected myocardial infarction, hypovolemia, diabetic conditions and others—or the risk factors that indicate these conditions are possible—should be transported to the emergency department.

     As mentioned earlier, all patients are screened and treated for life threats during the primary (initial) assessment. Position the patient appropriately for his condition and administer oxygen as necessary based on his presentation and pulse oximetry readings.

     While many of the possible causes of syncope are transient, you will treat those you are able to identify (hypovolemia, hypoglycemia) and choose appropriate transport locations for patients who require specific interventions, such as those with suspected myocardial infarction and stroke.

     Syncope patients pose challenges for the prehospital clinician in several ways. In most cases, signs and symptoms are no longer present. There are a wide variety of causes of syncope, many of which can't be diagnosed even at the ED. Yet, the patient did have a condition that caused a brief loss of consciousness and may be potentially serious. It will be up to you to gather the appropriate facts to make solid clinical decisions in this elusive condition.

     Daniel D. Limmer, AS, EMT-P, is a paramedic with Kennebunk Fire-Rescue in Kennebunk, ME.

     Joseph J. Mistovich, MEd, NREMT-P, is a professor and chair of the Department of Health Professions at Youngstown (OH) State University.

     William S. Krost, MBA, NREMT-P, is director of Emergency Services & Health System Access for Blanchard Valley Health System in Findlay, OH.