For patients experiencing reflex‐mediated syncope, there is an inappropriate stimulation of the parasympathetic nervous system. It offsets or overwhelms the appropriate sympathetic response. These patients experience hypotension, with or without bradycardia. The resultant lack of cerebral perfusion results in a syncopal episode.
An additional etiology of syncope is hemorrhage. Common causes include gastrointestinal bleeding, ectopic pregnancy, and hemorrhagic ovarian cysts. These are in essence a “distributive shock” cause from the perspective of the central nervous system.
Neurogenic syncope, as a pure cause of transient loss of consciousness, is actually a rare event. Many of the neurologic events that result in syncope have poorly explained mechanisms. Additionally, many neurologic events that involve loss of consciousness are incorrectly labeled as syncope. It is important to note, however, that some neurologic causes of syncope represent serious pathologic processes, such as subarachnoid hemorrhage and transient ischemic attack. It is rare that such diseases manifest as a syncopal episode, but these potential diagnoses should be considered.
Assessment
The first task in assessing and managing syncope is to separate syncope from the other potential reasons for a loss of consciousness. First, any nontransient loss of consciousness, by definition, is not syncope. A patient who has a loss of consciousness from hypoglycemia, requires IV dextrose, and then awakens to a normal level of consciousness has not had a syncopal episode. Likewise, if the patient has a complex, nonmotor seizure and then recovers from a postictal state to a normal mental status, this, too, is not syncope. However, for the EMS clinician, all of these situations can be dispatched as “altered mental status,” “unconscious,” or “syncope,” depending on local dispatch protocols and the information provided by the 9‐1‐1 caller. This can incorrectly prejudice EMS clinicians to presume or discount syncope as the diagnosis.
Patients frequently present with “presyncope” or “near syncope.” These patients did not lose consciousness and, therefore, by definition, did not have a syncopal event. It is debatable whether these situations should be treated as syncope or not. Some authors have suggested that patient outcomes are the same, and therefore both presyncopal and syncopal patients should receive the same treatment [8]. For the purposes of this discussion, both patient populations will be considered to be the same.
As with all medical problems, proper assessment and evaluation begin with an appropriate but focused history and physical examination. Although 85% to 90% of all patient pathology can be determined by history and a physical, these are even more important in the case of syncope. Very few diagnostic tests will aid in determining the cause of a syncopal episode or in ascertaining syncope as the problem versus another malady. If one takes a diagnosis such as appendicitis, we know that it can be determined clinically almost 90% of the time, but it also can be “confirmed” by computed tomography scanning, by surgical findings, or by the pathology results. However, in the case of a syncopal episode, few laboratory or other diagnostic studies aid significantly in the diagnosis.
History is the most important aspect of evaluation. For patients in the prehospital setting, the history obtained by EMS clinicians is vital. Because true syncope involves a loss of consciousness, there will be details of the event that patients will not be able to convey. Frequently, these patients arrive alone to the ED, and the emergency physician has no opportunity to interview others who may have witnessed the episode. Therefore, maximizing history obtained at the scene through witness interviews and relaying this information to the ED staff is pivotal to accurate diagnosis and treatment.
It is important to ask the patient what he or she can remember before the event. No recollection at all is of particular importance. If the patient felt no prodromal symptoms, and then had a period of unconsciousness, this is particularly concerning for cardiac causes of syncope. Chest pain, palpitations, and shortness of breath are other symptoms that can be associated with dysrhythmia or other cardiac pathology. Abdominal pain, nausea, or lightheadedness frequently precede reflex‐mediated syncope. The EMS clinician should always attempt to ascertain the last thing the patient remembered before the event, as well as the first thing he or she remembered after regaining consciousness. In the case of a true syncopal event, the patient will not be able to recall information during his or her period of unconsciousness. Bystander interviews are important, and as mentioned previously, EMS personnel may be the only clinicians able to obtain this relevant information. Did the bystanders notice anything before the patient lost consciousness? Was there any seizure activity noted (tonic/clonic, focal, etc.)? Where there any periods of apnea noted?
Bystander‐provided history is also imperative for determining the length of the unresponsive period. Unfortunately, this time interval will frequently be overestimated due to the anxiety provoked in seeing someone unresponsive. Still, thoughtful and compassionate interviews by EMS personnel can frequently elucidate valuable references to attempt to establish a time course. Was the patient unconscious for the entire 9‐1‐1 phone call? How long before EMS arrival did the patient regain consciousness?
Finally, EMS clinicians must obtain the bystanders’ history of events as the patient regained consciousness. Did the patient’s mental status improve rapidly or was there a period of confusion? Did the patient have any complaints on awakening that he or she cannot recall now? Did the patient appear hot or cold, sweaty, or pale? If the bystanders took the patient’s pulse, what was the rate and quality?
Beyond the history of present illness, EMS clinicians should obtain other pertinent medical history. Chronic health problems such as cardiac, vascular, or neurologic issues need to be documented because they are important risk factors in syncope. A complete medication list is important because many medications can predispose a patient to syncope. Additionally, medications can frequently point to other causes of loss of consciousness that are not syncopal episodes, such as seizures or hypoglycemia. Last oral intake should be ascertained to determine if the patient is at risk for hypoglycemia and to identify potential confounders to the mental status examination, such as drugs or alcohol.
A focused physical examination is always important for any complete patient assessment. Vital signs; skin condition; heart, lung, and abdominal examination; and thorough neurologic examination are essential. Many recommend checking orthostatic vital signs, at least lying and sitting. However, there are many confounders to positive or negative orthostatic vital signs and even much debate as what are the appropriate and inappropriate changes, though there are consensus guidelines on the blood pressure parameters [9]. Moreover, if the patient becomes symptomatic with changes in position, this is important to note.
Remember that, at the time of EMS assessment, the physical examination may be completely normal. Vital signs may be within normal limits, and the remainder of the examination may be unremarkable. Unfortunately, this does not preclude the presence of serious pathology. Cardiac syncope in particular is likely to present with a normal physical examination, despite being potentially lethal.
Consistent with most prehospital encounters, diagnostic testing is of limited value. A glucometer reading should be obtained, although glucose derangement rarely causes transient loss of consciousness.
A prehospital 12‐lead ECG is indicated because this may help risk‐stratify the patient’s potential syncopal etiology. Even in the hospital setting, the 12‐lead ECG is the only Class 1 recommendation for diagnostic studies for a syncope evaluation [10]. The following ECG findings are considered diagnostic for syncope due to a dysrhythmia [11]:
Persistent sinus bradycardia <40 bpm
Repetitive sinoatrial blocks or sinus pauses