Fainting - Causes and Symptoms

Definition

Fainting is a sudden and temporary loss of consciousness, followed by a spontaneous awakening with rapid psycho-physical recovery.

Fainting is typically associated with the loss of postural tone: the unconscious patient appears immobile and flaccid, with cold extremities, weak pulse and breath. The sudden loss of consciousness can be preceded by premonitory symptoms, such as nausea, weakness, yawning, blurred vision, sweating and a light-headed sensation.

In most cases, fainting is due to a decrease in cerebral perfusion, which often results from reduced cardiac output. In essence, little blood reaches the brain.

Other times, there may be an adequate cerebral blood flow, but an insufficient substrate (oxygen and / or glucose) for brain cells. In this regard, hypoglycemia is the main cause; it is in fact rare that hypoxia develops to such an extent as to trigger a sudden loss of consciousness (with the exception of diving or high altitude accidents).

The reduction in cardiac output can be found in cases of structural heart defects, arrhythmias, obstruction of blood flow and cardiac pathologies with systolic or diastolic dysfunction. The fainting, therefore, can be a consequence of valvular diseases, thrombosis, cardiac tumors, myocarditis, pulmonary embolism, acute myocardial infarction and heart failure.

Frequent fainting is orthostatic hypotension, a condition that can occur, for example, due to deconditioning caused by prolonged lodging or the use of some drugs.

Less often, the symptom is a consequence of cerebrovascular diseases (such as migraine, stroke and transient ischemic attacks) or severe cervical arthrosis.

Fainting can also occur due to vasovagal (ie neuro-cardiac) causes, including increased intrathoracic pressure (eg pneumothorax, hypertension), anaphylaxis and particularly unpleasant physical or emotional stimuli (eg pain, sight of blood and fear) .