Syncope and Postural Hypotension (Orthostatic Hypotension)

Edited by: Joe Hing Kwok Chu

Syncope

Syncope is a brief loss of consciousness caused by a temporary deficiency of oxygen in the brain, also called swoon or blackout.

Causes of Syncope

I. Arrythmia

1. overly slow heart rate (may be caused by shenyangxu (kidney yang deficient) condition.

2. overly fast heart rate  (may be caused by shenyinxu (kidney yin deficient) condition.

3. irregular heart rate (may be caused by xinqixu (heart qi dficient) condition.

II. Hemodynamic -- obstruction to blood flow

1. Obstruction of the flow of blood out of the left ventricle due to hypertrophy of the ventricular subaorta. [Idiopathic Hypertrophic Subaortic Stenosis (IHSS)]

2. blockage of the aorta

3. hypertension or clots in the lung circulation.

III .Neurally mediated

1. pneumogastric nerve reaction  (usually related to emotional stress)

2. over sensitivity of the nerve that controls the blood pressure

IV. Postural hypotension

usually caused by medication or dehydration.

Postural Hypotension 體位性低血壓

When a person changes his/her position from lying down to standing, and the systolic pressure drops 20 mm and diastolic pressure drops 10 mm, it is called postural (or orthostatic ) hypotension.

Postural hypotension can be classified into:

1. idiopathic hypotension

2. secondary postural hypotension

Per 1. idiopathic hypotension

Idiopathic hypotension is usually caused by disorders of the  vegetative (or automatic) nervous system which cause the small arteries to be unable to constrict in time. Symptoms include low blood pressure, unstable standing, blurry eye sight, dizziness, lack of strength,  incontinence, and in serious cases, syncope (sudden black-outs).

Per 2. secondary postural hypotension

Secondary postural hypotension usually occurs in diseases of the spine, acute or serious infections (like lobar pneumonia), endocrine disorder (like adreno-cortical hormone deficiency), heart failure, or chronic malnutrition. Secondary postural hypotension may also occur because of (or after cessation of) long-term use of  medication to lower blood pressure or sedative medication. Dehydration also causes the blood pressure to drop.

There are 5 types of drugs that can cause postural hypotension:

1. Hypertension drugs such as guanethidine sulfate (Ismelin) and ganglionic blocking agents are the most common. Other include: hydralazine, dihydralazine, pargyline hydrochloridum (Eutonyl), nifedipine,  (Adalat; Procardia)  (calcium channel blocking agents) and methyldopa (Aldomet, Dopamet). These types of drugs lower the tension of blood vessels and lower blood pressure. Long-term usage may cause postural hypotension.

2. Sedatives like Chlorpromazine injected into the muscle or veins may cause postural hypotension because of its anti-adrenogenic and anti-epinephrine effects which cause the lowering of the tension of blood vessels thus lowering blood pressure. These types of sedatives also dilate the small veins and hamper the return flow of circulation to the heart.  Clozapine is also known to have the side effect of causing postural hypotension. The occurrences of postural hypotension caused by this group of drugs were about 4%. ^［2］

3. Anti-epinephrine drugs like: Tolazoline, Benzazoline, and  Phentolamine are intended to affect  the α-adrenoceptors of norepinephrine that constrict the blood vessels.

4. Vaso-dilating drugs like: nitroglycerin (nitroglycerine, trinitroglycerin, or glyceryl trinitrate) are intended to relax the smooth muscles of the blood vessels.

5. Diuretics: loop diuretics such as furosemide, bumetanide, and ethacrynic acid

Postural hypotension is an easily obtained measurement that may help to identify middle-aged persons at risk for stroke. ^[1]

Treatment

If the symptoms are obvious, tight elastic stockings and waist bands can be used.

I. Traditional Chinese herb formulae commonly used in chronic postural hypotension according to TCM diagnostics.﹕

1. bu zhong yi qi tang,

2. shi quan da bu tang, 　

3. sheng mai yin

4. jin gui shen qi wan (if feet are cold, with shenyangxu (kidney yang deficient) syndromes.)

5. liu wei di huang wan (if feet not cold with shenyinxu (kidney yin deficient) syndromes.)

II. Western medicine: steroids like prednisone, fludrocortisone are commonly used, but they have undesirable long term side effects which include osteoporosis,  ulcers, memory loss, seizures, yeast infection, weakened auto-immune system, atrophy of thymus and adrenal glands, sodium retention, and  potassium deficiency. Steroids should only be used if patients show signs of adreno-cortical deficiency.

If the problem is caused by adrenocortical hormone deficiency, the body rejects sodium and retains potassium. This condition shows in patient with shenyangxu (kidney yang deficient) syndromes. Then, the patients should eat less of those foods that are high in potassium and may have to increase salt intake.

Note:

Blood pressure drops when the body is dehydrated. Because the feeling of thirst becomes dull as a person ages, it is important to monitor the intake of water.

Also see Vertigo.

^[1] M. Eigenbrodt et al

^[2] 沈漁﹐.精神病學，第3版，北京:人民衛生出版社，1994，11.