-IBIS-1.5.0-
tx
nervous system
fainting
diagnoses

definition and etiology

definition: Includes sudden loss, near-complete loss, and feeling of impending loss of consciousness. The medical term is "syncope".

etiology: The attack almost always occurs while the patient is in the upright position. There are many causes. The condition usually resolves quickly and spontaneously once the patient is put in, or falls to, a horizontal position, and blood flow, no longer hindered by gravity, once more flows fully to the brain.

• vasovagal: This is the typical faint that occurs in healthy people with no underlying condition. It can frequently be recurrent when the individual is faced with the same stimuli (e.g. a small, warm room), or can be due to an emotional shock, intense pain, and as a response to trauma. Other factors that might precipitate a faint in a susceptible person include being bedridden, fasting, anemia, and poor physical condition. Physiologically, there is a significant drop in arterial pressure concurrent with venous pooling of blood and tachycardia; next comes bradycardia which further reduces cerebral blood flow and initiates the faint. Almost always the loss of consciousness occurs gradually enough for the person to get to the ground without injuring himself.
Once on the ground, awareness usually resumes quickly, although the faint may last up to a half hour, but the patient may still feel weak, and rising too soon may bring on another faint.

• postural hypotension with syncope: This type of faint occurs in patients who have a chronic disorder or variable instability of vasomotor reflexes. The most common reason for this type of syncope is use of drugs that impair autonomic reflexes (typically excessive doses of hypotensive medications, monoamine oxidase inhibitors, the chemotherapy drug vincristine, barbiturates, alcohol, quinidine and L-dopa). The fall of blood pressure on arising is due to a loss of vasoconstriction reflexes in resistance and the dependent venous capacitance vessels resulting in a decrease of venous return and a drop in cardiac output. The characteristics of the faint are similar to that of the vasovagal type; the distinguishing feature is that the patient experiences the attacks upon rising from a sitting or stooping position and not after having stood awhile. Causes for this include the drugs listed above as well as familial tendencies, and the dysautonomias.

• syncope of cardiac origin: This usually results from a sudden lack of cardiac output, usually due to an arrhythmia. In normal people ventricular pulse rates below 35-40 beats per minutes or above 185 beats per minute are usually needed to induce a cerebral blood flow disorder causing syncope. The most common arrhythmia is complete atrioventricular block, and combined with subsequent fainting, is known as the Stokes-Adams-Morgagni Syndrome. It is not necessarily associated with the upright position. Other cardiac problems that can cause syncope include massive myocardial myofarction, stenosis (leads to exertional fainting), Tetralogy of Fallot, and primary pulmonary hypertension.

• cardiac sinus syncope: Massage of one or both of the cardiac sinuses, especially in the elderly individual, can cause cardiac slowing and/or decreased arterial pressure. This type of syncope may occur by turning the head, tight collars, shaving over the sinus regions, or, spontaneously without a clear stimulus. The typical patient is male, and the faint usually occurs in the upright position.

signs and symptoms

signs and symptoms (prodromal and faint):
• Yawning.
• Nausea, perspiration ("cold sweat").
• Hypernea, tachycardia (followed by bradycardia: in vasovagal syncope).
• Weakness, confusion.
• Dimness or loss of vision.
• Feeling of impending loss of consciousness.
• Paleness.
• All signs and symptoms disappear in the horizontal position.

lab findings:
• usually not pertinent unless the faint is suspected to be secondary to one of the pathologies mentioned
• CBC to rule out anemia

course and prognosis

The prognosis is excellent for victims of a vasovagal episode, as long as the patient does not injure himself on falling, and lays horizontally with feet elevated until complete recovery.

For the other types of syncope, prognosis depends upon the primary cause and the severity of the condition.

differential diagnosis

• Anxiety attacks and hyperventilation; hysterical fainting.
• Hypoglycemia.
• Acute/insidious hemorrhage.
• Cerebral ischemic attacks.
• Hypovolemia.


footnotes