Grades are shown as the source states them. Neither source grades its recommendations: both are expert consensus (a modified Delphi process for EUSEM; a consensus panel for orthostatic hypotension). The 2018 ESC guideline, which does grade its recommendations, could not be read under its publisher's terms and is listed as further reading.
Key recommendations
Transient loss of consciousness (a brief loss of consciousness with complete recovery) has several non-traumatic causes: syncope, epileptic seizures, psychogenic episodes and rare causes. Call it syncope — global cerebral hypoperfusion from a fall in blood pressure — only after evaluation.
Contextualizing syncopesEuropean Society for Emergency Medicine (EUSEM) syncope group 2024
In anyone arriving with transient loss of consciousness, first identify trauma (including trauma as the cause of the episode) and shock, which is most often septic; either moves the person to a different pathway.
Part 1: arrival and triageEuropean Society for Emergency Medicine (EUSEM) syncope group 2024
Record a 12-lead ECG and have it interpreted by an experienced clinician within 10 minutes of registration; only a normal ECG counts as low risk.
Part 2; Table 3European Society for Emergency Medicine (EUSEM) syncope group 2024
Stratify syncope of uncertain cause using the ESC risk categories: low-risk patients can be discharged to primary or outpatient care; high-risk patients need monitoring and admission; anyone neither low nor high risk needs further work-up and observation, not direct discharge.
Part 3: risk stratificationEuropean Society for Emergency Medicine (EUSEM) syncope group 2024
Screen routinely for orthostatic hypotension in people with Parkinson's disease, multiple system atrophy, pure autonomic failure or dementia with Lewy bodies; anyone with an unexplained fall or syncope; autonomic neuropathy (for example diabetes or amyloidosis); people aged 70 or over who are frail or take several medicines; and anyone whose symptoms occur only on standing.
Screening for nOHAmerican Autonomic Society and National Parkinson Foundation consensus panel 2017
Diagnosis
Orthostatic hypotension is a sustained fall in systolic pressure of at least 20 mmHg or diastolic pressure of at least 10 mmHg within 3 minutes of standing (or head-up tilt). With supine hypertension (150/90 mmHg or more), a fall of 30/15 mmHg may be the better criterion.
Introduction; Blood pressure testingAmerican Autonomic Society and National Parkinson Foundation consensus panel 2017
Symptoms include light-headedness or dizziness on standing, feeling about to black out, falls with or without syncope, blurred vision, leg buckling, aching across the neck and shoulders (‘coat hanger’ pain) and breathlessness on standing — easing on sitting or lying, and often worse in the morning and after meals.
Screening for nOH; Table 1American Autonomic Society and National Parkinson Foundation consensus panel 2017
A rise in heart rate of less than 15 beats a minute with orthostatic hypotension suggests a neurogenic cause; a larger rise (20 or more with volume depletion) suggests a non-neurogenic one. The rule does not apply with beta-blockers or other rate-limiting drugs, a pacemaker or conduction disease.
In-clinic monitoring; Medication reviewAmerican Autonomic Society and National Parkinson Foundation consensus panel 2017
Partial loss of consciousness carries a similar prognosis to full loss and follows the same pathway.
Part 1: arrival and triageEuropean Society for Emergency Medicine (EUSEM) syncope group 2024
Some people develop orthostatic hypotension only after 3 minutes of standing (delayed orthostatic hypotension), and large or carbohydrate-rich meals or alcohol can cause falls in blood pressure after eating; measure before and after meals when symptoms follow food.
In-clinic monitoring; Post-prandial hypotensionAmerican Autonomic Society and National Parkinson Foundation consensus panel 2017
Investigations
Check vital signs (blood pressure, heart rate, oxygen saturation, respiratory rate, temperature). The minimum blood tests are glucose and haemoglobin; others depend on the suspected cause, such as serial troponin for myocardial infarction and D-dimer for pulmonary embolism or aortic dissection.
Tables 1 and 2European Society for Emergency Medicine (EUSEM) syncope group 2024
Major high-risk ECG findings include acute ischaemia, Mobitz II or complete heart block, atrial fibrillation slower than 40 a minute, persistent sinus bradycardia below 40 or pauses over 3 seconds while awake, bundle branch block or other conduction disturbance, ventricular hypertrophy or signs of ischaemic heart disease or cardiomyopathy, sustained or non-sustained ventricular tachycardia, pacemaker or ICD malfunction, a type 1 Brugada pattern and a QTc over 460 ms on repeated ECGs.
Table 3European Society for Emergency Medicine (EUSEM) syncope group 2024
Minor high-risk ECG findings, which count only when the history suggests an arrhythmia, include Mobitz I block, a markedly prolonged PR interval, asymptomatic bradycardia of 40–50 a minute, paroxysmal supraventricular tachycardia or atrial fibrillation, pre-excitation and a short QTc (below 340 ms).
Table 3European Society for Emergency Medicine (EUSEM) syncope group 2024
Measure blood pressure after at least 5 minutes lying, then at 1 and 3 minutes of standing; seated-to-standing is an acceptable alternative. If the test is negative but symptoms strongly suggest orthostatic hypotension, repeat lying-to-standing or use head-up tilt. Guard against falls during testing.
In-clinic monitoringAmerican Autonomic Society and National Parkinson Foundation consensus panel 2017
When orthostatic hypotension is found, take a history, examine, and check an ECG, blood count, electrolytes, urea and creatinine, glucose, TSH and vitamin B12 to look for non-neurogenic causes.
Exclude other causes; Table 2American Autonomic Society and National Parkinson Foundation consensus panel 2017
If clinic testing is negative in someone at risk, use home blood pressure readings (lying, then after 3 minutes standing, on rising, when symptomatic and at bedtime), 24-hour ambulatory monitoring with a posture diary, or specialist autonomic testing.
At-home monitoring; Specialty testingAmerican Autonomic Society and National Parkinson Foundation consensus panel 2017
Treatment
Treat orthostatic hypotension to reduce symptoms — especially falls — lengthen standing time and restore daily function, not to normalise standing blood pressure. Work in four steps, allowing about 2 weeks for each: review medicines, add non-drug measures, try one drug, and only then combine drugs, with great caution.
Treating nOHAmerican Autonomic Society and National Parkinson Foundation consensus panel 2017
Step 1: reduce or stop medicines that lower blood pressure, including diuretics, vasodilators and nitrates, alpha-blockers (such as tamsulosin or doxazosin), beta-blockers, antidepressants (particularly tricyclics), dopaminergic drugs and phosphodiesterase-5 inhibitors.
Step 1; Table 3American Autonomic Society and National Parkinson Foundation consensus panel 2017
Step 2: about 2 litres of fluid a day unless the heart limits it; drinking about 500 mL of water quickly raises blood pressure for up to an hour; extra salt (up to 1–2 teaspoons a day) unless heart failure or oedema rules it out; smaller meals; avoiding heat; and correcting anaemia and vitamin B12 deficiency.
Step 2: non-pharmacological measuresAmerican Autonomic Society and National Parkinson Foundation consensus panel 2017
Raise the head of the bed by 15–23 cm (pillows are not enough), and use waist-high compression or an abdominal binder; knee-high stockings do not help. Recumbent exercise such as a stationary bicycle or swimming builds strength with less risk of falling.
Step 2: head-up sleeping; compression; physical conditioningAmerican Autonomic Society and National Parkinson Foundation consensus panel 2017
When syncope has a clear cause (such as aortic stenosis or complete heart block) or is part of another illness (such as pulmonary embolism, aortic dissection or sepsis), manage that condition.
Part 2: diagnostic proceduresEuropean Society for Emergency Medicine (EUSEM) syncope group 2024
Supine hypertension often accompanies neurogenic orthostatic hypotension, and treating one can worsen the other. In most people treat the orthostatic hypotension first; avoid lying flat by day, sleep head-up, and treat severe supine hypertension (over 180/110 mmHg) only with a short-acting drug at bedtime, avoiding diuretics and long-acting antihypertensives.
Supine hypertensionAmerican Autonomic Society and National Parkinson Foundation consensus panel 2017
Important geriatric considerations
Fall-related injury after transient loss of consciousness is commonest in older people, many with cognitive impairment, so the history may be unreliable; look actively for injuries such as intracranial bleeding.
DiscussionEuropean Society for Emergency Medicine (EUSEM) syncope group 2024
Many older people drink too little, sometimes deliberately to control urinary urgency or frequency; low fluid intake is the commonest readily treatable contributor to orthostatic hypotension.
Blood volume repletionAmerican Autonomic Society and National Parkinson Foundation consensus panel 2017
Some people hide symptoms or falls for fear of losing their independence, so ask specifically about falls and their circumstances.
Screening for nOHAmerican Autonomic Society and National Parkinson Foundation consensus panel 2017
Older people are more prone to drops in blood pressure after meals; smaller, more frequent meals help.
Post-prandial hypotension; DietAmerican Autonomic Society and National Parkinson Foundation consensus panel 2017
Drug doses
Midodrine: 2.5–15 mg once to three times daily during waking hours, titrated to symptoms, and not within 5 hours of bedtime because of supine hypertension; watch for urinary retention, and take care in heart failure and chronic kidney disease.
MidodrineAmerican Autonomic Society and National Parkinson Foundation consensus panel 2017
Fludrocortisone (off-label): 0.1–0.2 mg a day, with little added benefit above 0.3 mg; acts over 3–7 days; causes supine hypertension, low potassium and oedema; use with caution in heart failure.
FludrocortisoneAmerican Autonomic Society and National Parkinson Foundation consensus panel 2017
Droxidopa (approved in the United States for neurogenic orthostatic hypotension) and pyridostigmine (off-label, 30–60 mg up to three times a day, which does not worsen supine hypertension) are other options; there are no head-to-head trials to guide the choice.
Droxidopa; Pyridostigmine; Recommendations for initiating nOH treatmentAmerican Autonomic Society and National Parkinson Foundation consensus panel 2017
When to refer
Refer severe orthostatic hypotension (able to stand for less than 5 minutes, together with a systolic fall over 30 mmHg or a severe effect on daily activities) or failure of drug treatment to a clinician experienced in autonomic disorders.
Grading of nOH; Referring the nOH patientAmerican Autonomic Society and National Parkinson Foundation consensus panel 2017
Patients at intermediate or high risk need hospital-based care with monitoring, in or outside the emergency department.
Part 3: risk stratificationEuropean Society for Emergency Medicine (EUSEM) syncope group 2024
Red flags
Any major high-risk ECG finding, trauma, or signs of shock at presentation.
Part 1; Table 3European Society for Emergency Medicine (EUSEM) syncope group 2024
Keep re-evaluating: emergency-department and hospital discharge diagnoses of transient loss of consciousness often differ.
DiscussionEuropean Society for Emergency Medicine (EUSEM) syncope group 2024
Recent updates
The 2024 EUSEM consensus turns the 2018 ESC guideline into an emergency-department process that starts from unexplained transient loss of consciousness rather than an established syncope diagnosis. It reflects a small expert group and needs confirmation.
Abstract; LimitationsEuropean Society for Emergency Medicine (EUSEM) syncope group 2024