Low blood pressure

Introduction Hypotension refers to a state in which the systemic arterial pressure is lower than normal. Hypotension Because high blood pressure often causes damage to important organs such as the heart, brain and kidney, it is highly valued. The standard World Health Organization for hypertension also has clear regulations, but there is no uniform standard for the diagnosis of hypotension. Adults are generally considered to be Lower limb blood pressure is lower than 12/8 kPa (90/60 mmHg). Physiological hypotension usually does not require special treatment, but should be followed up regularly, because some so-called physiological hypotension can change to hypotension under certain circumstances, or it may be pathological hypotension, but only early It can be found that the pathological changes are mistaken for physiological hypotension.

Cause

Classification of causes:

They are generally divided into acute and chronic categories according to the onset of hypotension.

First, acute hypotension: refers to the patient's blood pressure suddenly or significantly decreased from normal or high levels, clinically often due to brain, heart, kidney and other important organ ischemia dizziness, black eyes, soft limbs, cold sweat, palpitations, less Symptoms such as urine, severe cases of syncope or shock.

Second, chronic hypotension: refers to the state of blood pressure continued to fall below the normal range, most of which are related to the patient's constitution, age or genetic factors, clinically referred to as constitutional hypotension; hypotension and position changes in some patients (especially The upright position is called orthostatic hypotension; and the hypotension associated with nervous, endocrine, cardiovascular and other systemic diseases is called secondary hypotension.

1. Physical hypotension;

2, orthostatic hypotension:

(1) idiopathic orthostatic hypotension;

(2) supine hypotension syndrome;

(3) Secondary orthostatic hypotension.

3, secondary hypotension:

(1) Nervous system diseases: syringomyelia, multiple sclerosis, amyotrophic lateral sclerosis, myasthenia gravis, etc.

(2) Endocrine and metabolic diseases: pituitary dysfunction, adrenal insufficiency, hypothyroidism, diabetic neuropathy, etc.

(3) Cardiovascular diseases: severe aortic or mitral stenosis. Congestive heart failure, constrictive pericarditis, pericardial effusion, thick obstructive cardiomyopathy, multiple arteritis (no pulse).

(4) Chronic wasting diseases: malignant tumors, severe tuberculosis, malabsorption syndrome, etc.

(5) Insufficient blood volume: diarrhea, vomiting, massive dehydration, excessive diuresis, excessive sweating, excessive blood loss, etc.

(6) iatrogenic: sedative, hypnotic drugs, dilated vascular drugs, sympathetic (including ganglion) block drugs, diuretics, dehydrating agents, antidepressants, chlorpromazine and so on.

(7) Others: such as high altitude hypotension, carcinoid syndrome.

mechanism

The formation of blood pressure mainly depends on the three factors of blood circulation, peripheral vascular resistance and circulating blood volume. The three can adapt to each other and coordinate with each other to ensure the relative stability of blood pressure. This coordination is mainly achieved by the regulation of nerve fluid. Regardless of the factors that cause one or more of the above three factors to impair or impair synergy, it will inevitably lead to abnormal changes in blood pressure, such as decreased blood flow to the heart, decreased peripheral vascular resistance, and/or insufficient circulating blood volume. Causes a decrease in blood pressure, which in turn causes an increase in blood pressure. Refer to the Hypertension section for information on the regulation of blood pressure. The following is an example of the occurrence of orthostatic hypotension.

In normal people, the sympathetic nerve excitability decreases, the blood vessel wall tension decreases, and about 700 ml of blood accumulates in the lower limb blood vessels due to gravity when standing upright, so that the blood supply to the head and neck is reduced, through the aortic arch and Carotid sinus baroreceptor reflex causes increased sympathetic excitability. On the one hand, it increases cardiac output by increasing heart rate and strengthening myocardial contractility. On the other hand, it can reduce lower extremity congestion by increasing vascular tone. Of course, lower limb muscle tension when standing. Increasing the compression of blood vessels (especially veins) and promoting blood reflux also play an important role. The result of these compensations ensures that only a short period of arterial systolic blood pressure drops (normally 0.7-2.0 kPa or 5-15 mmHg) when the normal person takes the upright position, diastolic blood pressure does not drop or has an upward trend, and the mean arterial pressure Generally remain unchanged.

The occurrence of orthostatic hypotension is mainly related to the following mechanisms:

1 reduction of effective circulating blood volume: including absolute lack of blood volume due to blood loss, loss of fluid, and relatively insufficient blood volume caused by vasodilators;

2 reduction of cardiovascular reactivity; mainly manifested by decreased responsiveness of the heart and blood vessels during sympathetic excitation, clinically mainly seen in elderly, frail, long-term bedridden or chronic wasting diseases;

3 autonomic nervous system dysfunction: often block a part of the baroreflex arc, so that the peripheral vascular tension can not change with the body position changes, sympathetic (gangl) blockers, peripheral sympathetic ganglion (chain) resection, spinal cord The orthostatic hypotension caused by lesions or injuries, diabetic neuropathy, vascular motility surrounding lesions (such as fourth ventricle tumors), certain central sedatives, antidepressants, etc. are related to this; 4 increased release of vasodilators: Such as histamine 5 serotonin, bradykinin, prostaglandin and the like increased blood levels caused by peripheral vasodilation.

an examination

The diagnosis of hypotension depends not only on the patient's blood pressure level, but also on the patient's presence or absence of blood pressure reduction, such as brain, heart, kidney and other major organs, because of long-term hypotension without any symptoms (especially It occurs in young people) and can be considered as a physiological phenomenon. It has no important clinical significance. Only those with obvious clinical symptoms should be considered. Examine carefully to find out the cause and treat it accordingly.

First, medical history

The medical history has an important role in the diagnosis of the cause of hypotension. Young women, blood pressure is lower than normal, but there is no discomfort, especially those with family genetic background support the diagnosis of constitutional hypotension; dizziness, darkness and other cerebral insufficiency related to postural changes, after excluding cervical spondylosis or arrhythmia Should consider postural hypotension; black (skin pigmentation), thin (slim), low (hypotension, hyponatremia) is a characteristic of Addison's disease; female patients, cold, hair loss, pale, body temperature Low, slow pulse rate and low blood pressure suggest a hypothyroidism. In addition, patients with hypotension should pay attention to the history of recent medication, especially the application history of sedatives, antihypertensive drugs, and antiarrhythmic drugs.

Second, physical examination

In addition to paying attention to the measurement of supine and standing blood pressure, patients with hypotension should pay attention to the comparison of blood pressure between the upper limbs and the upper and lower limbs to exclude arterial stenosis caused by multiple arteritis. In addition, attention should be paid to the patient's face when examining the body. Skin color, hair distribution, fat and thin, with no edema, etc.; heart examination should pay attention to changes in heart sounds and heart murmurs; neurological examination should pay attention to patients' limb sensation, exercise and mutual economic function.

Third, the laboratory and special inspection

According to the medical history and physical examination, the clues of the diagnosis of the cause of hypotension can be obtained, but if the diagnosis is established, it is necessary to rely on the necessary laboratory or special examination. If you suspect diabetes, you need to carry out blood. Urine sugar determination, cardiovascular disease needs to be confirmed by echocardiography or even cardiovascular angiography; endocrine disease diagnosis requires evidence of pituitary, adrenal gland or thyroid function test.

Differential diagnosis

First, physical hypotension

Physique hypotension, also known as primary hypotension, is mainly seen in people with weak constitution, especially in women aged 20-40, and may have a family genetic predisposition. Although most patients with constitutional hypotension have significant hypotension, they have no symptoms of discomfort and are only found when they are examined. The low blood pressure of such patients can last from childhood to old age, even for life, and does not affect the life of the patient. A small number of patients may have fatigue, dizziness, palpitations and other non-specific symptoms in the presence of fatigue, hunger, dehydration, etc., or in the post-physical weakness period. In severe cases, there may be syncope episodes, which should be differentiated from secondary hypotension. The main reason is that patients with constitutional hypotension have a long history of hypotension without organic disease affecting blood pressure. The age of onset and family genetic background also have certain significance for differential diagnosis.

Second, orthostatic hypotension

Orthostatic hypotension refers to the hypotension that occurs when the supine position is suddenly changed to the upright position or when standing for a long time. According to whether the cause is clear or not, it is divided into secondary and idiopathic.

1, idiopathic orthostatic hypotension:

Idiopathic orthostatic hypotension is an orthostatic hypotension of unknown cause. It is more common in middle-aged patients and more men than women. The mechanism may be related to systolic dysfunction of the orthostatic arteries caused by autonomic dysfunction. Recently, some studies have found that the plasma level of norepinephrine in the patient's position is normal or low, but it does not increase correspondingly when standing or exerting force, and the plasma dopamine -hydroxylase level is also low, indicating the disease. The mechanism by which the sympathetic nerve is activated in the patient is impaired. In addition, some researchers have injected intra-arterial injection of tyramine into the patient's disease and found no normal vasoconstriction response of the anterior arm and hand. Intra-arterial injection of norepinephrine enhanced the vascular response, indicating that the sympathetic nerve endings are norepinephrine depletion. It may also be one of the mechanisms that cause this disease.

The clinical features of idiopathic orthostatic hypotension are: 1 cerebral ischemic symptoms with different degrees of standing position, such as weakness, dizziness, vertigo, soft legs, transient black sputum, etc., severe stun can occur, or even Therefore, it causes a fall; 2 the prodromal symptoms are not obvious, and the episodes are not accompanied by pale, sweating, nausea, heart rate changes, etc., the duration of the episode is short (several seconds to several minutes), and the episodes are more common in summer or morning; 3 have autonomic dysfunction independent of body position changes, such as impotence, no sweat, rectal bladder dysfunction, etc., after a few years, extrapyramidal (such as limb muscle tension, coarse tremor, activity reduction X cerebellum) Balanced or ataxia movement disorder) and the involvement of the cone system (such as warm reflex sputum into the disease is mainly based on the systolic blood pressure drop of 3.99 kPa (30mmHg) and/or diastolic blood pressure drop of 1.99 kPa (15mmHg) in the upright position Above or with an electrocardiogram to observe heart rate changes less than 6 times / min deep breathing, of course, norepinephrine intravenous titration test or vertical and horizontal plasma catecholamine determination of autonomic nervous function evaluation also has a certain significance.

2. Secondary orthostatic hypotension:

Secondary orthostatic hypotension refers to secondary neurological disease and endocrine disorders. Malnutrition or orthostatic hypotension caused by certain drugs, although there are blood pressure drops associated with postural changes (erect) and brain blood supply disorders associated with blood pressure drop, but more importantly, it has a clear cause. check.

3, supine hypotension syndrome:

This syndrome can occur in pregnant women in the second trimester of pregnancy and in patients with large abdominal tumors in the supine position. The main clinical manifestations are sudden drop of blood pressure and increased heart rate accompanying the supine position. In severe cases, syncope may occur. The cause is associated with an enlarged uterus or a large tumor of the abdominal cavity that mechanically compresses the inferior vena cava, resulting in a sudden decrease in blood flow to the heart. The above symptoms can be relieved when the patient is placed on the side or in the sitting position.

Third, secondary hypotension

(1) Nervous system diseases

In the case of neurological diseases such as syringomyelia, multiple sclerosis, myasthenia gravis, Guillain-Barré syndrome, etc., in addition to the typical sensory and/or dyskinesia, the affected limbs are often rough, Autonomic nerve involvement such as sweating disorder and decreased blood pressure.

(two) endocrine diseases

1, pituitary hypofunction (Simmon Yixi syndrome):

This disease is one of the more common endocrine diseases in adults. The cause is mainly the destruction of pituitary structure or function caused by various reasons, including the following: 1 compression and infiltration of pituitary and nearby tumors; 2 postpartum hemorrhage Adenine pituitary avascular necrosis and atrophy; 3 bacterial (including tuberculosis), virus, fungal infections caused by pituitary damage; 4 pituitary surgery, trauma or radiation damage. The disease is often manifested in a variety of complex syndromes caused by a lack of pituitary hormones, but often caused by gonadotropin and prolactin at the earliest and more serious, such as postpartum no milk, amenorrhea, genital atrophy. Patients with thyroid stimulating hormone (TSH) and adrenocorticotropic hormone ACTH) may develop symptoms characterized by decreased blood pressure, clinical manifestations similar to hypothyroidism and adrenal insufficiency (see below for hypopituitarism) Direct evidence for clinical diagnosis is the multiple determination of plasma levels of pituitary hormones below normal.

2, primary hypothyroidism (referred to as primary hypothyroidism):

Primary dysfunction refers to hypothyroidism caused by destruction of thyroid tissue due to thyroid disease itself. It is common in women. The main clinical manifestations are decreased metabolic rate, such as chills, hair loss, less sweat, fatigue, and body temperature. Low, loss of appetite, lethargy, bradycardia, etc., severe cases of pericardial effusion or fluid edema. Hypotension is also common in primary hypothyroidism and is often a clue to clinical diagnosis. In addition to the history and clinical manifestations, the diagnosis of primary hypothyroidism depends mainly on the determination of plasma thyroxine. When primary hypothyroidism, T3 and T4 levels decrease, and TSH levels increase. Primary hypothyroidism should be differentiated from secondary hypothyroidism caused by hypothalamic or pituitary dysfunction. In addition to hypothyroidism, the latter often have multiple endocrine gland dysfunction, such as the adrenal gland. , gonads, etc.; In addition, the decrease in plasma TSH levels is also a strong evidence that is different from primary hypothyroidism.

3, primary chronic adrenal insufficiency (Addison disease):

The disease is more common in the elderly, and hypotension and skin pigmentation are important features. The etiology of this disease mainly includes: 1 autoimmune damage of the adrenal cortex; 2 microbes (tuberculosis, fungi, etc.) infection; 3 tumor destruction or infiltration. Clinical manifestations of aldosterone and cortisol secretion characteristics, the former such as hyperkalemia, hyponatremia, fatigue, weight loss, orthostatic (upright) hypotension and other serious cases can also occur syncope or shock (see adrenal crisis); It is often manifested as a decline in body response or stress, such as fatigue, lethargy, hypoglycemia, amenorrhea, and decreased sexual function. Skin porcine pigmentation and the like. Hypotension is seen in most patients, but if the patient has hypertension, the blood pressure after the illness can be no less than normal. Orthostatic hypotension is also common in this disease, mainly related to hypovolemia caused by insufficient blood volume.

The diagnosis of Addison's disease relies mainly on the determination of urinary 17-hydroxyl-ketone and plasma cortisol as well as the results of the ACTH stimulation test. Plasma cortisol and urinary 17-hydroxyl, 17-ketone were often lower than normal, ACTH levels were elevated (usually greater than 55 pmol/L), and ACTH stimulation tests showed adrenal insufficiency (no significant increase in hematuria corticosteroids). Addison's disease should be differentiated from secondary adrenal insufficiency and chronic wasting disease caused by pituitary dysfunction. Secondary adrenal insufficiency: 1 syndrome with pituitary structure or impaired function; 2 patients with pale skin, no pigmentation; 3 plasma ACTH levels decreased and ACTH stimulation test indicates elevated blood cortisol levels or delayed rise high. Chronic wasting disease, tumors, tuberculosis, etc., although there may be a decrease in urinary 17-hydroxy 17-ketone, but the ACTH stimulation test showed a significant increase in blood urinary corticosteroid levels, which can be distinguished from primary adrenal insufficiency.

(3) Cardiovascular diseases

High aortic or mitral stenosis, massive pericardial effusion, thick obstructive cardiomyopathy with chronic constrictive pericarditis, etc. due to reduced cardiac output, may also be associated with hypotension, and have their own typical clinical features, For example, in the aortic stenosis, the aortic valve area systolic jet murmur mitral stenosis, the pear-shaped heart and apical diastolic rumbling murmur, characteristic echocardiographic manifestations of pericardial effusion or constrictive pericarditis In patients with hypertrophic obstructive cardiomyopathy, the systolic murmur of the 3-4 intercostal space of the left sternal border of the sternum is enhanced with the left ventricular anterior load to reduce the spleen qi, the nitroglycerin is increased, or the myocardial contractility is only exercised. When multiple arteritis involves the subclavian artery, there may be circulatory disorders such as weakened or disappeared arteries of the affected limb, decreased or undetected blood pressure, and weakness, numbness, cold sensation, and intermittent pain after exercise.

(4) drug-induced hypotension

Improper use of some clinical drugs can also cause blood pressure lowering or orthostatic hypotension. These drugs include: -blockers, -blockers, calcium ion antagonists, angiotensin-converting enzyme inhibitors. , diuretics, certain antiarrhythmic drugs (quinidine, procain phenolamine, etc.), sedative hypnotics, antidepressants, sympathetic ganglion blockers (such as guanethidine), chlorpromazine.

(5) Others

1. High altitude hypotension:

After 4-6 months of relocation of plain residents to the plateau above 3,000 m above sea level, low blood pressure and cerebral hypoxia may occur. The mechanism may be related to high altitude hypoxia or excessive histamine content and adrenal dysfunction.

2, carcinoid syndrome:

Carcinoid is a argyrophilic cell tumor with a tissue structure similar to cancer. More than 90% of it occurs in the gastrointestinal tract, especially in the appendix, the end of the ileum, and the rectum. Because cancer cells can secrete a variety of vasoactive substances such as serotonin, bradykinin, histamine and other peptide hormones, clinical paroxysmal flushing, gastrointestinal disorders (abdominal pain and diarrhea), bronchial asthma, etc. can occur clinically. symptom. Hyper-serotoninemia can also damage the right heart valve, especially the pulmonary valve and the tricuspid valve, causing inflammation or stenosis of the corresponding valve. Vasodilatation can cause an acute or sustained decrease in blood pressure. The diagnosis of this disease is more difficult, clinical manifestations such as unexplained diarrhea, paroxysmal flushing or asthma, liver enlargement (induced liver metastasis) should consider the possibility of this disease, urinary serotonin and 5-hydroxyindole The acid (5-HIAA) assay is helpful for diagnosis.

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