Browse categories and answer follow-up questions to refine your symptom profile.
Approach to the Critical Patient
Immediate stabilization and high-risk triggers
Time-critical priorities
Airway compromise
If airway risk, airway support and escalation
If hypoventilation, bag-valve-mask ventilation
Circulation instability
If SBP <90 mm Hg or shock index >1, resuscitation bay
If ongoing chest pain, acute coronary syndrome pathway
If severe dyspnea or hypoxia, pulmonary embolism pathway
If active GI bleeding, hemorrhage pathway
Neurologic emergency
If persistent focal deficit, stroke pathway
If prolonged altered mental status, broaden differential
Dangerous arrhythmia
If VT, VF, or unstable SVT, ACLS algorithm
If bradycardia with instability, ACLS bradycardia algorithm
Immediate bedside checks
Glucose
If <3.0 mmol/l, dextrose therapy
If >20 mmol/l with dehydration, hyperglycemic emergency pathway
12-lead ECG within 10 minutes
New ischemia
High-grade AV block
Pre-excitation
QTc prolongation
Brugada pattern
Ventricular paced rhythm with symptoms
Continuous cardiac monitoring
Ectopy burden
Pauses
Rate variability
Pulse oximetry
If SpO2 <92% on room air, hypoxemia evaluation
Focused bedside ultrasound when unstable
Pericardial effusion with tamponade physiology
Right ventricular dilation or strain pattern
Poor LV contractility
IVC size and collapsibility trend
Core definitions and initial framing
Clinical framing
Transient loss of consciousness with rapid onset, short duration, complete spontaneous recovery
Syncope
Presyncope without complete LOC
Mimics
ICD-10
R55 syncope and collapse
SNOMED CT concepts
Syncope
Vasovagal syncope
Orthostatic hypotension
Cardiac arrhythmia
Initial classification buckets
Reflex syncope
Vasovagal
Situational
Carotid sinus syndrome
Orthostatic hypotension
Volume depletion
Autonomic failure
Medication-related
Cardiac syncope
Arrhythmic
Structural or obstructive
Non-syncope transient LOC
Seizure
Hypoglycemia
Intoxication
Psychogenic pseudosyncope
History
Event characterization
Episode features
Context and activity
Exertional
Supine
Postural change
Prolonged standing
Heat exposure
Prodrome
Nausea
Diaphoresis
Warmth
Visual dimming
Palpitations
Witnessed description
Sudden collapse without prodrome
Duration of LOC
Abnormal movements
Cyanosis
Snoring respirations
Recovery phase
Immediate return to baseline
Post-event confusion
Persistent symptoms
Injuries
Head strike
Facial trauma
Anticoagulant use at time of fall
Symptom and risk context
Symptoms suggesting dangerous causes
Chest pain
Dyspnea
Back pain
Severe headache
Abdominal pain
Melena or hematochezia
Fever
Cardiac risk factors
Known heart failure
Known coronary artery disease
Prior ventricular arrhythmia
Prior MI
Known valvular disease
Congenital heart disease
Family history red flags
Sudden unexplained death <50 years
Inherited arrhythmia syndromes
Cardiomyopathy
Medications and exposures
QT-prolonging agents
Rate-limiting agents
Diuretics
Alpha blockers
Nitrates
Recent medication changes
Alcohol
Recreational stimulants
Comorbidities
Diabetes with hypoglycemia risk
Parkinson disease
Peripheral neuropathy
Chronic kidney disease
Anemia or bleeding disorder
Prior episodes and baseline function
Pattern and recurrence
First episode
Recurrent similar episodes
Increasing frequency
Baseline cardiovascular symptoms
Exertional intolerance
Orthopnea
Paroxysmal nocturnal dyspnea
Functional capacity
Recent decline
Frailty indicators
Prior workup
Prior ECG abnormalities
Prior echocardiography
Prior ambulatory monitoring
Prior EP evaluation
Physical Exam
Vital signs and orthostatic assessment
Hemodynamic assessment
Supine HR and BP
Persistent hypotension
Relative bradycardia
Standing HR and BP
Orthostatic hypotension criteria
Postural tachycardia pattern
Temperature
Fever as alternate diagnosis trigger
SpO2
Hypoxemia as PE or pulmonary trigger
Cardiovascular and volume status
Cardiovascular exam
Heart sounds
Harsh systolic murmur
Fixed split S2
New murmur
JVP and peripheral edema
Volume overload signs
Elevated JVP with hypotension
Pulse exam
Pulse deficit
Irregularly irregular rhythm
Volume status exam
Mucous membranes
Capillary refill
Skin turgor
Orthostatic symptoms reproduction
Neurologic and trauma assessment
Neurologic screen
Focal deficit
Gait instability
Speech disturbance
New tremor or rigidity
Head and neck
Scalp hematoma
Cervical tenderness
Tongue laceration
Skin findings
Pallor
Diaphoresis
Urticaria or angioedema
PITFALLS
Common pitfalls
Normal vitals after event does not exclude serious cause
Seizure-like movements can occur in syncope
Orthostatic vitals can be falsely normal after fluids
Murmur absence does not exclude severe aortic stenosis
Differential Diagnosis
Life-threatening causes
Immediately dangerous etiologies
Cardiac arrhythmia
Ventricular tachycardia
High-grade AV block
Sick sinus syndrome with pauses
Acute coronary syndrome
STEMI equivalent patterns
NSTEMI with malignant arrhythmia
Pulmonary embolism
Massive or submassive
Hypoxemia or RV strain pattern
Aortic dissection
Chest or back pain
Pulse deficit
Cardiac tamponade
Hypotension
JVP elevation
Severe hemorrhage
GI bleeding
Ectopic pregnancy
Subarachnoid hemorrhage
Thunderclap headache
Neck stiffness
Common benign or intermediate causes
Non-life-threatening syncope categories
Vasovagal syncope
Prodrome with nausea and diaphoresis
Triggered by pain, emotion, standing
Situational syncope
Micturition
Defecation
Cough
Post-exercise
Orthostatic hypotension
Volume depletion
Medication effect
Autonomic dysfunction
Carotid sinus hypersensitivity
Head turning
Tight collars
Mimics of syncope
Non-syncope transient LOC or collapse
Seizure
Postictal confusion
Lateral tongue bite
Prolonged recovery
Hypoglycemia
Diaphoresis
Neurocognitive symptoms
Intoxication
Sedatives
Alcohol
Psychogenic pseudosyncope
Prolonged apparent unresponsiveness
Normal hemodynamics
Drop attacks
Sudden falls without LOC
TIA or vertebrobasilar insufficiency
Focal deficits
Diplopia or ataxia
Laboratory Tests
Targeted ED labs
Core labs by scenario
Pregnancy test for people who can become pregnant
Ectopic pregnancy risk stratification
Imaging pathway trigger
Hemoglobin for bleeding concern
Trend if ongoing loss suspected
Transfusion thresholds by clinical status
Electrolytes for arrhythmia risk
Potassium abnormalities
Magnesium abnormalities
Creatinine and eGFR for contrast planning
CT angiography feasibility
Medication dosing implications
High-sensitivity troponin for ischemia concern
Chest pain
ECG ischemia
Known CAD with concerning features
BNP or NT-proBNP for heart failure concern
Dyspnea
Volume overload signs
Point-of-care and bedside tests
Bedside tests
Capillary glucose
Hypoglycemia confirmation
Hyperglycemia with dehydration trigger
Venous blood gas when shock or respiratory concern
Lactate for hypoperfusion
pH and CO2 for ventilatory failure
Stool occult blood when GI bleeding uncertain
Context-dependent interpretation
Limited utility in overt bleeding
Lab interpretation pitfalls
Limitations
Routine broad lab panels without clinical triggers
Low diagnostic yield for syncope alone
False positives driving unnecessary admission
Troponin elevation
Demand ischemia vs type 1 MI differentiation
Chronic elevation in CKD
D-dimer
Appropriate only with low-to-intermediate PE pretest probability
Age-adjusted thresholds when validated locally
Diagnostic Tests
Scoring Systems
Risk stratification tools
Canadian Syncope Risk Score
ED diagnosis elements
Vasovagal predisposition
Cardiac syncope features
Clinical features
SBP in ED
History of heart disease
ECG features
QRS axis abnormality
QRS duration prolongation
QTc prolongation
Biomarkers
Elevated troponin
Outputs
30-day serious adverse event risk estimate
Disposition support adjunct
San Francisco Syncope Rule
CHF history
Hematocrit low
Abnormal ECG
Shortness of breath
SBP <90 mm Hg
Use limitations
Clinical gestalt integration requirement
Local validation variation
Not a replacement for ECG interpretation
MRI
MRI indications
Suspected seizure focus with recurrent unexplained LOC
Neurology referral pathway trigger
Outpatient vs inpatient planning
Suspected posterior circulation stroke with persistent deficits
MRI brain with diffusion-weighted imaging
Vascular imaging if indicated
MRI limitations
Low yield in isolated uncomplicated syncope
Access and time constraints in ED
CT
CT head
Indications
New focal neurologic deficit
Persistent altered mental status
Significant head trauma
Anticoagulation with concerning head injury
Low-yield contexts
Uncomplicated syncope with normal neuro exam
Return to baseline without trauma
CT pulmonary angiography
Indications
Syncope with PE concern
Hypoxemia
RV strain on ECG or POCUS
CT aorta
Indications
Syncope with tearing chest or back pain
Pulse deficit
New aortic regurgitation murmur
Ultrasound
POCUS applications
Cardiac
Pericardial effusion
LV systolic function gross estimate
RV dilation pattern
IVC assessment
Collapsibility trend for volume responsiveness
Integration with clinical exam
Lower extremity venous ultrasound
DVT evidence supporting PE diagnosis
Adjunct when CT unavailable
Carotid ultrasound
Not routine for syncope without focal neurologic signs
Consideration only with TIA or stroke features
Disposition
Admission and monitoring criteria
Higher level of care triggers
Abnormal ECG suggestive of arrhythmia or ischemia
New AV block
Ventricular tachyarrhythmia evidence
Ischemic changes
Structural heart disease with syncope
Aortic stenosis suspicion
HCM suspicion
Persistent hypotension or recurrent syncope in ED
Ongoing IV fluid requirement
Pressor requirement
Significant anemia or active bleeding
Transfusion need
Endoscopy pathway
PE, ACS, dissection, or tamponade concern
Immediate specialty consultation
Transfer if capability mismatch
Observation unit appropriateness
Intermediate risk without clear serious diagnosis
Telemetry for 6-24 hours depending on risk
Repeat ECG if symptoms recur
Ambulatory monitoring planning
Patch monitor
Event recorder
Discharge criteria
Safe discharge features
Clear vasovagal or orthostatic mechanism
Typical prodrome
Trigger identified
Normal ECG without high-risk history
No known structural heart disease
No exertional or supine syncope
Normal vital signs after observation
No recurrent episodes in ED
Able to ambulate at baseline
Reliable follow-up access
Primary care or cardiology
Return precautions understood
Consult and transfer triggers
Specialty involvement
Cardiology
Abnormal ECG
Suspected structural disease
Need for echo or EP evaluation
Neurology
Persistent focal deficit
High suspicion seizure disorder
Obstetrics
Pregnancy with bleeding or abdominal pain
Pregnancy with hemodynamic instability
Treatment
General supportive care
Supportive measures
Supine positioning
Legs elevated for suspected vasovagal or orthostatic component
Reassessment of perfusion markers
IV access
Two large-bore lines if hemorrhage or shock concern
Blood products pathway if indicated
Fluids for suspected hypovolemia
Isotonic crystalloid bolus 500-1000 ml
Reassessment after each bolus
Medication review adjustments
Hold contributing antihypertensives when appropriate
Hold diuretics if volume depletion suspected
Arrhythmia-directed therapy
Bradycardia with instability
Atropine protocol
Atropine IV 1 mg
Repeat every 3-5 minutes
Maximum 3 mg
If ineffective, transcutaneous pacing
Sedation and analgesia if time allows
Pads placement and capture confirmation
If pacing not available or bridging, catecholamine infusion
Epinephrine infusion 2-10 micrograms/min
Dopamine infusion 5-20 micrograms/kg/min
Tachyarrhythmia with instability
Synchronized cardioversion
Immediate energy escalation per rhythm
Sedation if stable enough
Ventricular tachycardia with pulse and stable
Amiodarone IV 150 mg over 10 minutes
Repeat as needed for recurrent VT
Infusion 1 mg/min for 6 hours
Then 0.5 mg/min for 18 hours
Torsades de pointes
Magnesium sulfate IV 2 g
Repeat once if recurrent
Potassium target 4.0-4.5 mmol/l
If bradycardia-associated, overdrive pacing or isoproterenol
Long QT and QT-prolonging drugs
Offending agent discontinuation
QTc reassessment after correction
Electrolyte optimization
Cause-specific therapy
Acute coronary syndrome suspected
Antiplatelet therapy per ACS pathway
Contraindications screen
Reperfusion planning if STEMI
Nitrates avoidance when RV infarct or severe aortic stenosis suspected
Pulmonary embolism suspected
Anticoagulation when no contraindications and diagnosis likely
Heparin pathway per institutional protocol
Thrombolysis consideration for massive PE
Anaphylaxis with syncope
Epinephrine IM 0.5 mg of 1 mg/ml
Repeat every 5-15 minutes if needed
Airway edema escalation trigger
Hypoglycemia
Dextrose therapy
Dextrose IV 10% 150 ml
Repeat based on glucose response
Long-acting carbohydrate when awake
Evidence and guideline anchors
Guideline highlights
12-lead ECG in initial evaluation is recommended (Class I)
Arrhythmia or ischemia detection utility
Risk stratification contribution
Routine comprehensive lab testing without clinical indication is not recommended (Class III)
Low diagnostic yield
Targeted testing preference
Risk stratification tools support but do not replace clinical judgment (Class IIa)
Observation vs admission decisions adjunct
Special Populations
Pregnancy
Pregnancy considerations
Physiologic changes
Lower systemic vascular resistance
Increased plasma volume
Supine hypotensive syndrome in later gestation
Dangerous pregnancy causes
Ectopic pregnancy
Hemorrhage
Pulmonary embolism
Medication safety
Avoid teratogenic antiarrhythmics when alternatives exist
Anticoagulation selection with obstetric input
Imaging considerations
Ultrasound-first strategy when feasible
Radiation risk-benefit documentation
Geriatric
Older adult considerations
Higher prevalence of cardiac syncope
Conduction disease
Structural heart disease
Polypharmacy effects
Orthostatic hypotension from antihypertensives
Bradycardia from beta-blockers
Injury risk
Lower threshold for head imaging when trauma and anticoagulation
Falls assessment integration
Autonomic dysfunction
Parkinson disease
Diabetic neuropathy
Pediatrics
Pediatric considerations
Most common etiology
Vasovagal syncope predominance
Dehydration contribution
Red flags for cardiac causes
Exertional syncope
Family history sudden death
Known congenital heart disease
ECG focus
QTc assessment
Pre-excitation
Brugada pattern suspicion
Disposition nuances
Pediatric cardiology follow-up when red flags
Sports restriction counseling when exertional syncope
Background
Epidemiology
Frequency and impact
Common ED presentation
High revisit rates in selected populations
Significant resource utilization
Age distribution
Bimodal peaks in youth and older adults
Higher adverse event risk with increasing age
Pathophysiology
Mechanistic categories
Reflex syncope
Increased vagal tone
Vasodilation with relative bradycardia
Orthostatic hypotension
Inadequate autonomic compensation to standing
Volume depletion contribution
Cardiac syncope
Abrupt drop in cardiac output from arrhythmia
Fixed obstruction limiting output augmentation
Cerebral perfusion threshold
Global hypoperfusion mechanism for LOC
Rapid recovery after perfusion restoration
Therapeutic Considerations
Management principles
Identify high-risk cardiac etiologies early
ECG-centered evaluation
Telemetry when indicated
Avoid low-yield testing in low-risk presentations
Targeted labs and imaging
Observation strategies
Recurrence prevention
Hydration strategies
Counter-pressure maneuvers education
Medication adjustment discussion
Outcomes focus
30-day serious adverse events as key metric
Discharge safety net and follow-up planning
Patient Discharge Instructions
Copy discharge instructions
Discharge guidance
Likely cause explanation
Vasovagal or orthostatic pattern if applicable
Trigger avoidance strategies
Hydration and salt guidance when appropriate
Increased fluid intake unless contraindicated
Slow position changes from lying or sitting
Activity and driving
Avoid driving until cleared if unexplained syncope
Avoid climbing ladders or heights until follow-up
Return to ED immediately
Chest pain
Shortness of breath
Recurrent fainting
Palpitations preceding faint
Severe headache
Weakness, numbness, facial droop, speech trouble
Black or bloody stools
Persistent vomiting
Follow-up plan
Primary care within 1 week
Cardiology within 1-2 weeks if abnormal ECG or risk factors
Ambulatory rhythm monitoring pickup instructions if arranged
References
Guidelines and evidence sources
Major guidelines
ACC/AHA/HRS Guideline for the Evaluation and Management of Patients With Syncope (Class I, IIa, IIb framework)
ECG recommended in initial evaluation (Class I)
Targeted testing strategy (Class I)
European Society of Cardiology (ESC) Syncope Guidelines
Reflex vs orthostatic vs cardiac classification
Risk stratification and observation pathways
ACEP Clinical Policy on Syncope
History, physical exam, and ECG as core evaluation (ACEP Level A)
Admission for high-risk features support (ACEP Level B)
Limited role for routine neuroimaging without focal deficit (ACEP Level B/C depending on scenario)
Decision tools and validation studies
Risk tools
Canadian Syncope Risk Score derivation and validation studies
30-day serious adverse event outcome focus
ECG and troponin integration
San Francisco Syncope Rule studies
External validation heterogeneity
Adjunctive use only
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.