Complementary and Alternative Healing University  現代中藥辭典

Postural Hypotension 體位性低血壓

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

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.

Hemodynamic -- obstruction to blood flow

1. Obstruction of the flow of blood out of the left ventricle due to hypertrophy of the ventricular sub aorta. (IHSS)

2. blockage of the aorta

3. hypertension or clots in the lung circulation.

Neurally mediated

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

2. overly sensitive of the nerve that control the blood pressure

Postural hypotension usually caused by medication or dehydration.

Postural Hypotension 體位性低血壓

When a person changes his/her lying position to standing and the systolic pressure drops 20 mm and diastolic pressure drops 10 mm, it is call 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 vegetative (or automatic) nervous system which cause the small arteries 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 infection or serious infection (like lobar pneumonia), endocrine disorder (like adreno-cortical hormone deficiency), chronic malnutrition. Secondary postural hypotension may also occur because of (or after cessation of) long-term usage of blood pressure lowering medication 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.

3. Anti-epinephrine drugs like: Tolazoline, Benzazoline, 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

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) )

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, weaken auto-immune system, atrophy of thymus and adrenal glands, sodium retention, potassium deficiency. They should not be used if patients do not 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 the those food that are high in potassium and may have to increase salt intake.

If the problem is caused by over abundance of mineralcorticoid hormone the body retainssodium and  rejects potassium. This condition shows in patient with shenyinxu (kidney yin deficient)  腎陰虛 syndromes. Then, the patients should eat more of the those food that are high in potassium and may have to decrease salt intake.

Note:

Blood pressure drops when the body is dehydrated. Feeling of thirst become dull as a person ages. It is important to monitor the intake of water.

Causes:

Treatment

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

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)

Western medicine like fludrocortisone is commonly used but it has undesirable long term side effects which include osteoporosis,  ulcers, memory loss, yeast infection, weaken auto-immune system, atrophy of thymus and adrenal glands, sodium retention, potassium deficiency. This should not be used if patients do not show signs of adreno-cortical deficiency.

supplys the sensation  of the ear, the tongue, the larynx, and the pharynx, motor impulses to the vocal cords, and motor and secretory impulses to the abdominal and thoracic viscera.

Reading material:

http://pmj.bmjjournals.com/cgi/content/full/75/881/185

一过性晕厥：也叫单纯性、血管神经性晕厥，多见于青少年。常因某种强烈刺激所引起，如恐惧、剧烈疼痛、亲人亡故等，引起反射性周围血管扩张，心排血量减少，血压突然降低，即可出现一过性晕厥。一过性晕厥多在站立中发生，有全身不适、心悸、胸闷、恶心、视物模糊的先兆。病人晕厥数秒或数分钟後可自醒，发作後无後遗症，但有暂时遗忘。对这类晕厥病人，应让其迅速平卧，保持头低足高体位，以改善其脑部血液供应，并解开患者的衣领和腰带等，使其保持呼吸道畅通。
    体位性低血压性晕厥：发作于卧位或下蹲位突然站起时，多见于老年人或久病常卧者。其原因是体位的突然改变，腹部和头部的血液迅速向下肢流去，供应头部的血液相对减少。出现暂时性脑缺血，表现为眼前发黑，持续时间短暂。对于这类病人，平素宜服一些补中益气丸，也应加强体育锻炼。患者在站立时应缓慢或扶物而起，不宜下蹲过久。
    低血糖性晕厥：多见于严重饥饿者或长时间进食很少，糖尿病酮症酸中毒和低血糖患者。对于这类昏厥病人，应迅速让其平卧，如神志清醒，可给予糖水。低血糖较严重，处于昏迷状态的，只要注射适量高渗葡萄糖，也可很快地清醒。
    心源性晕厥：是由于心脏功能异常，心排血量突然减少引起，这类晕厥多数发病突然，持续时间较长，病情也较凶险，应争人夺秒全力抢救。急救宜采用胸外脏按压术，并迅速呼叫救护车前来。
    排尿性晕厥：多在夜间起床排尿时发生，主要是突然起床和用力排尿後腹压急骤下降，以致上身血液回流腹腔，导致脑缺血而发生晕厥。对于这类晕厥，主要预防措施为夜间排尿时采取坐位，如站立小便时，应扶住物体，排便用力勿过大。
     剧咳性晕厥：机体在剧烈咳嗽时，胸腔和腹腔内压增高，会妨碍静脉血的回流，使心脏输出血量减少，导致脑部缺血缺氧。此外，咳嗽时脑脊液压力增大，颅内压升高，也会引起脑部的一时性缺血，从而导致晕厥。咳嗽晕厥只是一过性的脑缺血缺氧所致，其本身的後果一般并不严重，但由于突然发生摔倒时可造成严重的意外损伤，因此必须提高警惕。一旦发生剧烈的咳嗽时，身体应尽量放松，可采取坐位或半卧西半球，切忌频繁走动，有条件者可以吸氧。

體位性低血壓

由平卧忽然改為站立時 收縮壓下降20毫米汞柱或舒張壓下降10毫米汞柱，即為體位性低血壓。

體位性低血壓分為原發性(突發性)和继發性两型。

原發性多因植物神經功能紊亂，引起直立性小動脉收缩功能失調所致。主要表现是直立时血壓偏低，還可伴有站立不稳，视力模糊，頭晕目眩，软弱无力，大小便失禁等，严重时会發生晕厥。

继發性多见于脊髓疾病，急性传染病或严重感染(如大叶性肺炎)，内分泌紊乱，慢性营养不良或使用降壓药、镇静药之後。

　　體位性低血壓是老年人的常见病，据统计65岁以上老年人體位性低血壓者约占15%，其中75 岁以上的老年人可高达30%～50%。老年人由于心脏和血管系统逐渐硬化，大血管弹性纤维也会减少，交感神经增强，可使老年人收缩期血壓升高。長期偏高的血壓，不仅损害壓力感受器(位于颈動脉处)的敏感度，還会影响血管和心室的顺应性。当體位突然發生变化或服降壓药以後，在血壓突然下降的同时，缺血的危险性也大大增加。此外，老年人耐受血容量不足的能量较差，可能与其心室舒張期充盈障碍有关。因此，任何急性病导致的失水过多，或口服液體不足，或服用降壓药及利尿药以後，以及平时活動少和長期卧床的病人，站立後都容易引起體位性低血壓。

　　一旦發生體位性低血壓，应反复测量不同體位的血壓，以便明确诊断，對症治疗，避免因晕厥给病人带来不良影响。

　　體位性低血壓除病因治疗外，還应注意以下几点：

　　(1)合理飲食，补足营养，避免飲食过饱或饥饿，不飲酒。

　　(2)體育鍛煉，增强體质，充分的睡眠時間，避免勞累和長時間站立。

　　(3)症状明顯著者，可穿弹力長袜，用緊身腰带。對一些慢性體位性低血壓患者，可给對證用中藥治療﹕補中益氣丸,十全大補湯,　金櫃腎氣丸, 生脉飲。西藥常用腎上腺皮质激素 如 醋酸氟氫可的松　Fludrocortisone Acetate. 但是長期應用醋酸氟氫可的松可引起諸多不良附作用﹕如骨質疏鬆﹐記憶不良﹐胃潰瘍﹐黴菌感染﹐免疫機能低下﹐腎上腺與胸腺萎縮﹐等。 如非腎陽 症狀顯明者不應該用腎上腺皮质激素。

。

　　(4)為预防體位性低血壓發生，長期卧床的病人和患有高血壓的老年人，在站立时動作应缓慢，在站立前先做準備動作，即做些輕微的四肢活動，也有助于促进静脉血向心脏回流，升高血壓，避免體位性低血壓發生。

　　容易引起體位性低血壓的药物包括四類：

(1)抗高血壓药：以胍乙啶 Guanethidine 和神经节阻断药Ganglionic Blocking Agents 最常见，其他還有肼苯哒嗪 hydralazine 、双肼苯哒嗪 dihydralazine、優降寧 Pargylini Hydrochloridam  (Eutonyl) 和 α-甲基多巴 Methyldopa、Aldomet、Dopamet. 等。這類药物都能使血管緊張度降低，血管擴張和血壓下降。

(2)安定药：以肌肉或静脉注射氯丙嗪 Chlorpromazine 後最多见。氯丙嗪 Chlorpromazine 除具安定作用外，還有抗腎上腺素作用，使血管擴張血壓下降；另外還能使小静脉擴張，回心血量减少。

(3)抗腎上腺素药：如妥拉苏林 Tolazoline﹐ Benzazoline 、酚妥拉明 Phentolamine 等，它們作用在血管的α-腎上腺素受體 α-adrenoceptor (收缩血管的受體)上，阻断去甲腎上腺素的收缩血管作用。

4)血管擴張药：如硝酸甘油  Nitroglycerin ( nitroglycerine, trinitroglycerin, or glyceryl trinitrate)  等，能直接松弛血管平滑肌。

　　所以，在使用上述药物时，必须提高警惕，注意避免發生體位性低血壓。预防的方法有：

　　(1)告诉病人应用此類药物後不要突然站起，最好静卧1～2小时，站立後如有頭晕感觉，应继续卧床休息。

　　(2)用药後，夜间起床大小便最容易引起體位性低血壓，故夜间最好不入厕大小便。

　　(3)大量出汗、热水浴、腹瀉、感冒、飲酒等都是發生體位性低血壓的诱因，应该注意避免。清晨起床时须加小心。

　　一旦發生體位性低血壓，立刻將病人抬放在空氣流通處，或將頭放低，鬆解衣领，適當保温，病人一般很快甦醒。對發作持續較長而神智不清楚的病人，可针灸百会、人中、十宣，必要时皮下注射升壓药。由氯丙嗪 Chlorpromazine 所致的體位性低血壓禁用腎上腺素，因為腎上腺素具有 α 作用和 β 作用，而 α 作用可被氯丙嗪Chlorpromazine 所阻断，β作用就会突出地表现出来，引起某些血管擴張，使血壓进一步降低。此时可选用单纯興奮α受體的拟腎上腺素药 pseudoepinephrine ，如美速可新命，或新福林Synephrine 等，但纠正血壓效果也不可靠。