Fainting (Syncope)

You may assume that every brief blackout is a harmless faint, or that shaking during an episode proves it was a seizure. A straightforward faint is common, but temporary loss of consciousness can also result from an abnormal heart rhythm, a seizure, a blood pressure problem or another condition. Brief jerking can occur during syncope, so the movements alone do not establish the cause.

Syncope is a brief loss of consciousness Syncope is a temporary loss of consciousness caused by a short lived reduction in blood flow to the brain. You usually lose awareness and postural control, fall or slump, remain unconscious briefly, recover spontaneously, and regain awareness without resuscitation. Syncope is one form of transient loss of consciousness, often shortened to TLoC. Clinicians use this broader term for blackouts where the cause has not yet been established. Feeling faint is not always syncope You may experience light headedness, blurred or darkening vision, weakness, nausea, sweating, or a sense that you may collapse. If you remain conscious throughout, this is sometimes called presyncope or near fainting. Presyncope may have similar causes to syncope and still deserves assessment when it is recurrent, severe or associated with chest pain, palpitations or breathlessness. A reflex faint is common The commonest familiar pattern is often called a vasovagal or reflex faint. It may be triggered by prolonged standing, pain, fear, emotional distress, seeing blood, heat, dehydration, or a medical procedure. Before losing consciousness, you may feel warm, sweaty, nauseated, light headed, weak, visually dim or blurred, or aware of sounds becoming distant. You usually recover quickly after lying flat. This pattern is reassuring when the trigger, warning symptoms and recovery are all typical, but a clinician still considers your age, health history and the exact circumstances. Blood pressure may fall when you stand Postural hypotension means that your blood pressure falls after standing. It may cause dizziness, blurred vision, weakness, presyncope, fainting, or falls. Possible contributors include dehydration, blood pressure medicines, diuretics, prolonged bed rest, autonomic nervous system conditions, acute illness, or blood loss. Your clinician may compare blood pressure while you are lying or sitting with measurements after standing. Some faints occur during a specific action Situational syncope may occur during or immediately after coughing, passing urine, opening your bowels, swallowing, severe pain, or prolonged straining. The trigger may stimulate a reflex that lowers heart rate, blood pressure or both. A recognisable trigger can provide a clue, but repeated episodes still require review, especially when you are injured, have little warning or have heart disease. A heart problem may cause sudden syncope A heart related faint is important because it may occur with little or no warning. Possible causes include a very fast or very slow heart rhythm, a heart valve problem, disease of the heart muscle, reduced blood flow from the heart, an inherited electrical condition, or a problem involving an implanted pacemaker or defibrillator. Features that increase concern include: Fainting during exercise. Fainting while lying down. Sudden collapse without a warning sensation. Chest pain. Breathlessness. A pounding or irregular heartbeat. Known heart disease. An abnormal ECG. A sudden cardiac death at a young age in the family. A seizure can resemble a faint Both syncope and seizures can involve collapse, brief loss of awareness, stiffening, jerking, unusual breathing, and temporary confusion. Brief limb jerks can occur during a faint because the brain temporarily receives less blood. This is sometimes called convulsive syncope. Features that may be more suggestive of an epileptic seizure include: A strange sensory experience before the event. Head turning to one side. Sustained unusual posturing. Prolonged rhythmic jerking. A bitten tongue at the side. Prolonged confusion afterwards. No memory of abnormal behaviour witnessed by others None of these features is perfect. The whole sequence before, during and after the event matters. Other conditions can cause a blackout Temporary loss of consciousness or altered responsiveness can also occur with low blood glucose, alcohol or drug effects, severe blood loss, head injury, stroke or another neurological event, a psychological non epileptic event, sleep disorders, severe infection, or reduced oxygen. A person who appears unconscious but has not experienced syncope still needs assessment according to the likely cause and immediate risk. The witness may hold essential information You may not remember the fall itself. A witness may be able to describe what you were doing, whether you looked pale, whether you spoke or behaved unusually, whether your body became stiff, how long any jerking lasted. Whether your eyes were open, whether your head turned, how long you were unresponsive, how quickly you returned to normal, and whether you were confused afterwards. A written account can be useful. A safely obtained video may sometimes help specialists, but nobody should delay first aid or place you at risk to make a recording. What to do when you feel a faint approaching If you recognise warning symptoms: lie down if possible, raise your legs, if you cannot lie down sit and lower your head. Move away from stairs, roads, water or machinery, loosen restrictive clothing, remain down until the symptoms have fully settled, and stand gradually and with support. What to do if someone faints If someone collapses: check whether they respond, check whether they are breathing normally, if they are not breathing normally call 999 and begin CPR, if they are breathing and there is no serious injury lie them flat. Raise their legs where appropriate, protect them from traffic, water, heat and other hazards, do not make them stand immediately, and stay with them until they have recovered. Call 999 if they cannot be woken within one minute, have not recovered fully or meet any other emergency criterion. Recovery pattern matters A straightforward faint usually has rapid recovery once you are lying flat. You may feel tired, shaky, nauseated, sweaty or washed out. However, you should be able to communicate and gradually return to your usual state. Prolonged confusion, one sided weakness, severe headache, continued drowsiness or another episode without recovery suggests a different or more serious problem. Injury may be the most immediate harm A brief faint can still cause head injury, facial injury, fracture, burns, drowning, or a road collision. Assessment should consider both why you fainted and what happened during the fall. A person taking an anticoagulant may require urgent assessment after a significant head injury even when they initially feel well. A 12 lead ECG is an important initial test An electrocardiogram, or ECG, records the electrical activity of your heart. A 12 lead ECG is recommended during the initial assessment of transient loss of consciousness unless a clear reason prevents it. The clinician looks for rhythm or conduction abnormalities that may suggest a cardiac cause. A normal ECG does not exclude every heart condition. Further monitoring may be required if episodes remain unexplained or an intermittent rhythm disturbance is suspected. Other tests depend on the suspected cause Possible investigations include lying and standing blood pressure, blood glucose, full blood count, pregnancy testing where relevant, blood chemistry, ambulatory heart rhythm monitoring, echocardiography, exercise testing, specialist neurological assessment, and brain imaging in selected circumstances. Routine brain scans or EEGs are not required for every straightforward faint. Testing should answer a clinical question rather than investigate every possibility indiscriminately. Recurrent or unexplained episodes need follow up Arrange assessment when this is your first unexplained blackout, episodes recur, you have little or no warning, you have been injured, the diagnosis remains uncertain. Episodes affect work or safety, you have heart disease, you take medicines that may lower blood pressure, or symptoms occur while driving. Driving may need to stop A blackout can affect your fitness to drive. After unexplained loss of consciousness, do not drive until you have obtained medical advice about the cause and the applicable licensing rules. For car and motorcycle licences, some forms of fainting must be reported to the Driver and Vehicle Licensing Agency. Bus and lorry drivers must report blackouts, fainting or loss of consciousness.

Fainting is one possible cause of a temporary blackout. A safe assessment asks whether you completely lost consciousness, what happened immediately before, what a witness observed, how quickly you recovered, whether the episode occurred during exercise or lying down, and whether there were cardiac, neurological or bleeding warning signs. The priority is identifying whether a dangerous cause reduced blood flow or oxygen delivery to your brain.