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Situational syncope is often triggered by urination, swallowing, or coughing. [2] Carotid sinus syncope is due to pressure on the carotid sinus in the neck. [2] The underlying mechanism involves the nervous system slowing the heart rate and dilating blood vessels, resulting in low blood pressure and thus not enough blood flow to the brain. [2]
The carotid sinus baroreceptor can be oversensitive to manual stimulation from the pressure applied at the carotid sinus at the carotid bifurcation. It is a condition known as 'carotid sinus hypersensitivity' (CSH), 'carotid sinus syndrome' or 'carotid sinus syncope', in which manual stimulation causes large changes in heart rate and blood ...
Neurally mediated syncope may also occur when an area in the neck known as the carotid sinus is pressed. [1] A normal response to carotid sinus massage is reduction in blood pressure and slowing of the heart rate. Especially in people with hypersensitive carotid sinus syndrome this response can cause syncope or presyncope. [9]
[8] [9] Electrical stimulation of the external surfaces of the carotid sinus activates baroreceptors believed to be in the adventitia of the artery. This stimulates an afferent limb which activates central nervous system pathways that in turn exert two different but synergistic autonomic effects on the body.
Baroreceptors can also become oversensitive in some people (usually the carotid baroreceptors in older males). This can lead to bradycardia, dizziness and fainting (syncope) from touching the neck (often whilst shaving). This is an important cause to exclude in men having pre-syncope or syncope symptoms.
Often sinus node dysfunction produces no symptoms, especially early in the disease course. Signs and symptoms usually appear in more advanced disease and more than 50% of patients will present with syncope or transient near-fainting spells as well as bradycardias that are accompanied by rapid heart rhythms, referred to as tachycardia-bradycardia syndrome [4] [5] Other presenting signs or ...
Treatment may include drinking plenty of water or other fluids (unless the lightheadedness is the result of water intoxication in which case drinking water is quite dangerous). If a patient is unable to keep fluids down from nausea or vomiting, they may need intravenous fluids such as Ringer's lactate solution .
It conveys information from the baroreceptors of the carotid sinus to the vasomotor center in the brainstem (in order to mediate blood pressure homeostasis), and from chemoreceptors of the carotid body [further explanation needed] (mainly conveying information about partial pressures of blood oxygen, and carbon dioxide).