Syncope, Emergency Medicine

Transient loss of consciousness associated with loss of postural tone

Ultimately, it is the lack of oxygen to the brainstem reticular-activating system, which results in a loss of consciousness and postural tone.

Most commonly, an inciting event causes a drop in cardiac output.

Cerebral perfusion is re-established by autonomic regulation as well as the reclined posture, which results from the event.

Accounts for 3% of ED visits

Pregnant patients frequently experience presyncope or syncope from various causes. 5% of patients experience syncope, 28% experience presyncope throughout their pregnancy.

Placenta acts as an AV malformation, causing decreased SVR that potentiates orthostatic symptoms.

Fetus lying on IVC can lead to neurogenic and hypovolemic syncope.

Pregnant patients at higher risk of DVT/pulmonary embolism (PE), UTI, seizures (preeclampsia), valvular incompetencies. Must exclude these diagnoses in ED evaluation.

Elderly with highest incidence as well as increased morbidity

>1/3 will have numerous potential causes.

Etiology

Neutrally mediated syncope:

Reflex response causing vasodilatation and bradycardia with resulting cerebral hypoperfusion

Vasovagal (common faint):

Often incited by pain or fear

Prodromal findings are usually present.

Typically lasts <20 sec

Tilt-table testing is the gold standard to diagnose.

Carotid sinus syncope:

Cough, sneeze

GI stimulation (e.g., defecation)

Micturition

Orthostatic:

Positional changes cause abrupt drop in venous return to heart.

Volume depletion:

Severe dehydration (e.g., vomiting, diarrhea, diuretics)

Hemorrhage (see "Hemorrhagic Shock " ť)

Autonomic failure:

Diabetic or amyloid neuropathy

Parkinson disease

Drugs (e.g., Ž ˛-blockers) and alcohol

Cardiac arrhythmias:

Typically sudden and without prodromal symptoms

Tachydysrhythmia or bradydysrhythmia

Inherited syndromes (e.g., long QT syndrome, Brugada syndrome)

Advanced cardiac life support (ACLS) interventions for unstable patients

Oxygen

Cardiac monitoring

IV access with normal saline fluid bolus in suspected hypovolemia

Consider coma cocktail " ”dextrose, thiamine, and naloxone for persistent altered mental status

Ed Treatment/Procedures

ACLS interventions for dysrhythmias

Standard regimens for acute myocardial infarction

Control BP for subarachnoid hemorrhage and aortic dissection

Consider thrombolytics for submassive PE.

Medication

Dextrose: D50W 1 amp (50 mL or 25 g) IV (peds: D25W 2 " “4 mL/kg IV)

Naloxone: 2 mg IV or IM (peds: 0.1 mg/kg)

Thiamine: 100 mg IV or IM (peds: 50 mg)

Follow-Up

Disposition

Admission Criteria

San Francisco Syncope Rule identifies patients at high risk for serious short-term outcomes ( "CHESS " ť):

History of CHF

Hematocrit <30%

Abnormal ECG

Patient complaint of shortness of breath

Systolic BP <90

Other recommendations:

Suspected cardiac syncope must be admitted to monitored bed

GI bleeds consider intensive care unit bed

Admit elderly patients with syncope.

Discharge Criteria

Neutrally mediated syncope or orthostatic syncope from volume depletion may be evaluated on outpatient basis with close follow-up, if patient is reliable and has a good social structure.

Driving restrictions until cleared

Pearls and Pitfalls

Use of criteria such as the San Francisco Syncope Rule prevents unnecessary admissions.

Do not assume vasovagal cause in syncope associated with headache or chest pain.

Additional Reading

Brignole ‚ M, Alboni ‚ P, Benditt ‚ DG, et al. ESC guidelines on management (diagnosis and treatment) of syncope " ”update 2004. Executive summary. Eur Heart J. 2004;25(22):2054 " “2072.

Kessler ‚ C, Tristano ‚ JM, De Lorenzo ‚ R, et al. The emergency department approach to syncope: Evidence-based guidelines and prediction rules. Emerg Med Clin North Am. 2010;28:487 " “500.

Massin ‚ MM, Bourguignont ‚ A, Coremans ‚ C, et al. Syncope in pediatric patients presenting to an emergency department. J Pediatr. 2004;145(2):223 " “228.

Saccilotto ‚ RT, Nickel ‚ CH, Bucher ‚ HC, et al. San Francisco Syncope Rule to predict short-term serious outcomes: A systematic review. CMAJ. 2011;183(15):E1116 " “1126.

Yarlagadda ‚ S, Poma ‚ PA, Green ‚ LS, et al. Syncope during pregnancy. Obstet Gynecol. 2010;115(2):377 " “380.