Hypotension

Hypotension according to the mechanism of development, duration, clinical manifestations – a symptom of extremely heterogeneous.

There are many cases, especially among young people, when arterial hypotension is the only abnormal sign and is not accompanied by any disorder.

These cases are evaluated as a variant of the norm; they are called, at the suggestion of G. F. Lang (1929, 1938), physiological hypotension.

In the case of non-selective mass measurement of blood pressure among contingents aged 20–30 years, hypotension is recorded in 5–7% of individuals, about 1/3 of them occur in physiological hypotension.

For the lower limit of normal for adults up to 25 years is taken blood pressure, equal to 100/60 mm Hg. Art., for the age group of 25-40 years – respectively 105/65 mmrt. Art., in healthy women of young and middle age the lower limit of blood pressure is on average 5 mm Hg. Art. lower than in healthy men of this age.

It is practically permissible to assume that the lower limit of the norm for diastolic blood pressure does not change significantly with age (not higher than 65-70 mm Hg). To determine the lower normal limit of systolic pressure in people 50 years and older, it is proposed to add 50-55 to the age of the subject.

In most cases, however, hypotension is a pathological symptom. In some cases, blood pressure decreases rapidly – these are various options for pathological acute arterial hypotension, in others – hypotension persists for a long time with alternating periods of improvement and deterioration – this is chronic arterial hypotension.

When arterial hypotension clearly appears as a symptom of a particular disease, it is accordingly called secondary, symptomatic. In contrast, it distinguishes primary (essential) hypotension – neurocirculatory hypotension – a peculiar form of neurosis. There is also a special form of arterial hypotension – orthostatic – a sharp decrease in blood pressure, mainly systolic, with a rapid transition from a horizontal to a vertical position.

The term  “hypotension,” or hypotension,  refers to a decrease in systolic and diastolic blood pressure below the normal level. An isolated decrease in diastolic pressure, for example, in the case of insufficiency of the semilunar valves of the aorta or in case of thyrotoxicosis, is not called arterial hypotension. Reducing blood pressure in only one arm (as, for example, in Takayasu’s disease) should also not be attributed to arterial hypotension, since the latter implies a general reduction in blood pressure, more precisely, a reduction in central arterial pressure.

From a biophysical point of view, low blood pressure can be the result of a decrease in cardiac and minute cardiac output, a decrease in peripheral vascular resistance, a decrease in the BCC, a decrease in venous return of blood to the heart.

Changes in these major hemodynamic factors may occur in isolation or in combinations. Other factors can lead to a decrease in blood pressure: aortic stenosis (congenital aortic hypoplasia), reduced blood viscosity, but they are less common and play a smaller role.

Hypotension due to a decrease in shock and minute blood flow occurs in severe myocardial lesions (myocardial infarction, myocarditis, cardiomyopathy, severe arrhythmias, overdose of ß-blockers, etc.). The decrease in peripheral vascular resistance at the level of arterioles – precapillaries causes the occurrence of arterial hypotension during the collapse of infectious or toxic origin.

Close to the hemodynamic mechanism is hypotension in anaphylactic shock. External or internal bleeding (acute gastroduodenal, intestinal, spleen rupture, aortic aneurysm rupture, dissecting aortic aneurysm) cause arterial hypotension as a result of a decrease in BCC. With the rapid extraction of ascitic fluid, hypotension is the result of a sharp decrease in venous blood flow to the heart due to the retention of a significant portion of the BCC in the smallest dilated vessels of the abdominal cavity.

In various forms of chronic arterial hypotension, functional disorders of the higher vegetative centers of vascular regulation are most often detected; in some cases, a reduction in the function of the renin-angiotensin mechanism of blood pressure regulation, vascular receptor sensitivity to catecholamines, deficiency of corticosteroid hormones, and especially aldosterone in Addison’s disease or adrenal amyloidosis are established.

Orthostatic syndrome can occur as a result of impaired baroreflex at various levels with organic lesions and diseases of the nervous system:

• the afferent part of the arch can suffer with spinal tabes, chronic alcoholism, B- ₁₂ deficiency anemia, with hereditary Holmes-Adie syndrome (sharp decrease of tendon reflexes on the limbs, unilateral weakening of pupillary reactions);
• The efferent part of the baroreflex arc can be disrupted by spinal cord injury, a tumor, and damage to the sympathetic chain of postganglionic nerves (in acute and chronic polyneuropathy).

Orthostatic hypotension in dumping syndrome occurs due to an excess of bradykinins, which have a powerful vasodilator effect. Eating contributes to the release of kinin from the pancreas, duodenal and small intestine. A deficiency of kininases (absolute or relative) causes hyperkininism syndrome with a widespread vasodilator reaction causing arterial hypotension and other signs of the dumping syndrome. The rare hereditary syndrome of hyperkininism is also described (Struter, etc.).

Hypotension (acute and chronic) occurs in very many diseases. According to various sources, this symptom is detected in 15-25% of patients in the therapeutic and infectious departments. For the practical work of a physician, it is essential to know the diseases in which arterial hypotension occurs quite often, since it is important not only to clarify the diagnosis, but also to plan and adjust the system of therapeutic measures.

Although in most cases orthostatic hypotension is a symptom of various diseases, it rarely occurs as if an independent, primary form of this disease. Unlike various variants of symptomatic arterial hypotension, the considered form of idiopathic orthostatic hypotension is not accompanied by reflex tachycardia when the patient goes to orthostasis, therefore it is also called asimpathicotonic orthostatic hypotension. It is believed that the basis of the disease is the primary degeneration of the neurons of the lateral columns of the spinal cord. This form is characterized by a stable course, slowly or not progressing at all.

Diagnosis of arterial hypotension

Establishing the fact of low blood pressure (hypotension) requires further examination of a particular system, since this common symptom occurs in healthy people and in a wide variety of diseases, and as the most important manifestation of an independent nosological form. In the interest of diagnosis, it is first necessary to use a single classification.

Classification of hypotonic states

1. Physiological hypotension.
   1. Hypotension as an individual variant of the norm.
   2. Hypotension of increased fitness (in athletes).
   3. Adaptive hypotonia (among residents of highlands, tropics and subtropics).
2. Pathological hypotension.
   1. neurocirculatory hypotension (primary, essential):
      1. with unstable reversible course;
      2. severe form with persistent manifestations (hypotonic disease).
   2. Idiopathic orthostatic gypsony.
3. Symptomatic (secondary) hypotension:
   1. acute form (in shock, collapse);
   2. chronic form;
   3. form with severe orthostatic syndrome (including Shay-Drager syndrome).

Physiological hypotension is  established as a result of exclusion of disorders of a subjective or objective nature. Hypotension of high fitness (hypotension in an athlete) and adaptive hypotension (in highland residents and hot climates) can only be attributed to physiological hypotonia if the subjects do not have any painful symptoms.

It is not easy to distinguish physiological hypotonia from the initial stage of the NCG and latent symptomatic hypotension in an athlete, and not only in an athlete, and an individual approach and a comprehensive examination are needed here. This will contribute to a coherent analysis of the facts in the process of examining the patient.