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.