Immediate Management of Life-Threatening Problems Causing Syncope
See also Chapter 9.
Loss of consciousness due to cardiac arrest (ventricular fibrillation or asystole) from any cause occurs in 3–5 seconds if the patient is standing or within 15 seconds if the patient is recumbent. The patient usually rapidly regains consciousness if adequate cardiac output is restored promptly; most patients who regain consciousness within 12 hours will recover without neurologic sequelae.
Initiate cardiopulmonary resuscitation; see Chapter 9 for further details. Immediate hospitalization in an intensive care unit for evaluation and treatment is required.
See also Chapter 34.
See Table 18–1 for common causes of cardiac and neurologic related syncope. Palpitations, fatigue, dyspnea, or chest pain may precede loss of consciousness. Atypical chest pain (mainly nonexertional, left precordial, sharp, and of variable duration) suggests mitral valve prolapse.
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Rapid (≥160 beats/min), slow (≤50 beats/min), or irregular pulse must be carefully investigated. Tachycardia of 180–200 beats/min will produce syncope in half of healthy persons. In patients with underlying heart disease or atherosclerosis, tachycardia as fast as 135 beats/min or bradycardia as slow as 60 beats/min may result in loss of consciousness.
Chest auscultation with the patient in various positions (eg, sitting, left lateral decubitus, squatting) may disclose abnormal murmurs and clicks in the case of mitral valve prolapse. The electrocardiogram (ECG) may confirm the diagnosis of arrhythmia, heart block, sick sinus, or prolonged QT interval. However, a single ECG, obtained when the patient is asymptomatic, is frequently normal or nondiagnostic. A diagnosis can be firmly established only by demonstrating arrhythmias during symptomatic periods.
Patients with syncopal attacks thought to be due to structural cardiac disease or an arrhythmia should be hospitalized for further evaluation.
Evaluation of the Conscious Patient with a History of Syncope
The emergency department evaluation of the patient presenting with syncope consists of a careful history, a physical examination that includes orthostatic blood pressure measurements, and a 12-lead ECG. The initial goal should be to identify life-threatening causes of syncope.
Syncope is a symptom characterized by transient, self-limited loss of consciousness. It is associated with a loss of postural tone, usually resulting in falling. Syncope must be differentiated from other symptoms such as dizziness, presyncope, and vertigo, all of which do not result in loss of consciousness. Typically syncopal episodes are brief, lasting no longer than 20 seconds. Recovery from syncope is usually characterized by almost immediate restoration of appropriate behavior and orientation. Syncope should not be confused with other causes of loss of consciousness such as seizure hypoxia, hyperventilation, hypoglycemia, and intoxications.
In the awake patient with a history of one or more episodes of loss of consciousness, rule out blood loss due to various causes such as aortic aneurysm rupture, vaginal or gastrointestinal bleeding.
Supine hypotension (systolic blood pressure < 90 mm Hg) or severe peripheral vasoconstriction should be considered evidence of hemorrhagic shock until proven otherwise (Chapter 11).
Orthostatic vital signs should be obtained, though they may be contraindicated in patients who have supine hypotension; those in shock; and those with severe altered mental status, spinal injuries, or pelvic and lower extremity injuries. Measure blood pressure and pulse after the patient has been lying down for 3 minutes. Record blood pressure, pulse, and symptoms again after the patient has been standing for 1 minute. A positive test for orthostatic hypotension is an increase of pulse of 30 beats/min or more, or a decrease in systolic blood pressure of 20 mm Hg or less than 90 mm Hg. The presence of symptoms such as dizziness or syncope should also be noted as a positive test. Many conditions can produce postural hypotension in the absence of hypovolemia (Table 18–2). The utility of orthostatic vital signs in children is questionable.
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Use an intravenous catheter (≥18 gauge), and administer a crystallized solution (eg, normal saline) as needed. If blood loss is suspected and the hematocrit or hemoglobin is normal, a repeat determination after volume repletion may confirm blood loss. Serial CBCs may be helpful in detecting active bleeding, and a dextrose test may be helpful if the history or physical examination suggests hypoglycemia.
Nasogastric intubation may be indicated in suspected gastrointestinal tract bleeding or in syncope with unexplained postural hypotension. Check stool specimens for blood (gross and microscopic).
Consider pelvic bleeding (eg, ruptured ectopic pregnancy) or trauma, especially that is not visually obvious, such as splenic, hepatic, retroperitoneal, or pelvic injury. Look for a history of anticoagulant use.
Obtain an ECG. This quick, easy, noninvasive test is indicated in all cases of syncope except for those with an otherwise clear cause. ECG abnormalities suggesting an arrhythmic cause of syncope are listed in Table 18–1.
Patients with abdominal or pelvic pain may have hypovolemic syncope secondary to gastrointestinal hemorrhage, leaking aortic aneurysm, or ruptured ectopic pregnancy. Aortic dissection and rupture of a viscus into the peritoneal cavity may also produce syncope initially by vagal stimulation or later as a result of blood loss.
Consider myocardial infarction, pulmonary embolism (PE), tension pneumothorax, or dissecting aortic aneurysm.
Consider possible neurologic cause such as basilar artery insufficiency, migraine, and subclavian steal syndrome. Loss of consciousness as an isolated symptom is rarely if ever caused by basilar artery ischemia.
A detailed, accurate history from the patient, family, observers, or ambulance attendants is the most important factor in making the diagnosis. A head computed tomography (CT) scan must be obtained in the emergency department if the patient has focal neurologic findings or a history suggestive of subarachnoid hemorrhage as the etiology of syncope. The most helpful features are the following.
History of an epileptic aura preceding the loss of consciousness or a period of confusion (postictal state) upon regaining consciousness strongly suggests seizures as the diagnosis (see Chapter 19). This aura must be differentiated from symptoms of decreased cerebral blood flow (eg, those occurring before a syncopal episode or as a result of orthostatic hypotension or cardiac arrhythmia).
Episodes beginning when the patient is lying down suggest seizure or cardiac arrhythmia, whereas orthostatic hypotension and vasovagal syncope occur when the patient is standing or sitting up.
Syncope following active physical exertion is frequently noted in cardiac outflow obstruction (eg, aortic stenosis, hypertrophic obstructive cardiomyopathy, myxoma) and is elicited occasionally in patients with cardiac arrhythmias or pulmonary vascular disease.
Micturition and coughing are associated with distinctive syncopal syndromes. Simple fainting may occur during the first trimester of pregnancy and must be differentiated from syncope due to blood loss from ectopic pregnancy. Rare causes of syncope include glossopharyngeal neuralgia, hyperventilation, psychiatric causes, and Meniere’s disease (look for associated hearing loss and vertigo).
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