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FUNCTIONAL MONITORING OF THE CIRCULATORY SYSTEM



Registration of blood pressure. The most common way to control hemodynamics is the Riva-Rocci auscultation method using Korotkov sounds, however, it requires a number of conditions to be fulfilled to eliminate errors. So, to measure blood pressure in pregnant women should be in the position on the left side with the location of the cuff on the left hand.

In addition, the size of the cuff is important: if the cuff is superimposed on the asthenic “with a lap”, then often the true values ​​are understated. The cuff should cover 2/3 of the shoulder and overlap 2 cm above the elbow joint, so that under it it was possible to bring the finger of the subject. Cuffs that are not suitable for shoulder size can distort the results of measuring blood pressure by 10-30%, so you need to have the necessary set of cuffs: there are at least 5 sizes, starting with children’s. If the cuff is used wider than the specified sizes, then underestimated results are obtained, and already - overrated.

When measuring blood pressure in pregnant women, the level of diastolic pressure should be counted from the beginning of muffling tones (in non-pregnant women, the value of diastolic blood pressure is judged by the moment the sounds completely disappear). Therefore, for maternity hospitals, automatic blood pressure measurement systems are preferable (A.P. Zilber, 1997).

According to Cohn (1981), with arterial hypotension, true systolic blood pressure values ​​can be underestimated by an average of 34 mm Hg. Art., and in patients with heart failure - even 64 mm RT. Art. (!). This is due to the fact that at low system pressure, Korotkov noise becomes difficult to distinguish, and most often in the initial phases they are not captured. In this regard, in critical situations, the most objective way to register blood pressure is the direct method.

For registration of blood pressure in critically ill patients, catheterization of the radial or femoral artery is used. There are several sensor options for converting force into an electrical signal, followed by visualization on a monitor and recorder.

Complications of catheterization in the form of arterial partial occlusion are observed in 25%, and complete - in 3% of cases. It is approximately the same when catheterizing the radial or femoral artery.

BP indicators are normal:

a) systolic blood pressure (SBP) 100 - 140 mm RT. Art.

b) diastolic blood pressure (DBP) - 60 - 90 mm RT. Art.

The average dynamic pressure is determined by the formula:

SDD = (SBP + 2DAD) / W (E. Page, 1972) or SDD = DBP + PD / where PD (pulse pressure) = SBP - DBP

Norm SDD (mm Hg. Art.) = 70-105 mm Hg. Art.

An increase in blood pressure is most often possible with: activation of the sympathetic adrenal system (a wide variety of reasons), stress, increased general peripheral resistance, hypertension, cerebral edema, gestosis, pheochromocytoma, hypercapnia, etc.

A decrease in blood pressure occurs with collapse, shocks of various origins, loss of vascular tone, overdose of ganglion blockers and adrenolytics, coma, severe exicosis, epidural anesthesia, etc.

Pulse pressure is determined by the formula:

PD (mmHg) = GARDEN - DBP.

Normally - 40-60 mm Hg. Art.

An increase in this indicator is possible due to systolic pressure, the influence of a number of pharmacological agents: adrenergic agonists, cardiac glycosides; as a result of inadequate anesthesia with a decrease in vascular tone (a decrease in diastolic pressure and, as a consequence, an increase in pulse).

A decrease in the indicator is possible with various types of shock (especially often with cardiogenic), with compensated hypovolemia (due to an increase in total peripheral resistance).

Venous pressure. In different vessels, the venous pressure indicator is different. So, in a cubital vein, it is 9 - 12 mm Hg. Art., and in the superior vena cava - 3 - 8 mm RT. Art. (5 - 12 cm water column).

An increase in the indicator is possible with heart failure, hypervolemia, heart defects, mechanical ventilation with high peak pressure, lung diseases accompanied by an increase in pressure in the pulmonary artery (bronchial asthma, pneumonia, pulmonary edema, etc.)

A decrease in the indicator is observed with collapse, shock, hypovolemia, the use of drugs that lower peripheral vascular tone, the use of spinal anesthesia (especially against the background of decreased O CC).

Pulmonary artery pressure. Modern intensive care units are equipped with special equipment and catheters, allowing to obtain this highly informative indicator. To obtain data, a floating (flotation-balloon) catheter is used, which has a special balloon inflated with air, which is injected into the superior vena cava. With a blood stream, a catheter enters the pulmonary artery. With this manipulation, there is no need for x-ray control.

As the catheter advances through the heart cavities and blood vessels, the pressure parameters and the shape of the pressure curve change.

Catheterization of the right heart and pulmonary artery, like any invasive examination, is unsafe and can cause a number of complications:

- puncture of the subclavian vessel may be complicated by hemo- and pneumothorax, massive bleeding into the surrounding tissue;

- the presence of a catheter in the right ventricle and pulmonary artery may be accompanied by cardiac arrhythmias, ventricular fibrillation;

- there are reports of ruptures of the pulmonary artery;

- as with any vascular catheterization, there is a likelihood of thrombophlebitis and thromboembolism in the pulmonary artery system.

However, the risk present during this diagnostic procedure becomes justified if the results obtained can significantly affect medical tactics.

the superior vena cava pressure curve has a venous profile and is called central venous pressure. Normal values ​​are 0 to 4 mmHg. Art. (according to V.A. Koryachkin et al. (1999) - 3-8 mmHg). These indicators correspond to pressure in the right atrium. When a catheter passes through a tricuspid valve and enters the right ventricle, a wave of systolic pressure appears, and the wave of diastolic pressure remains unchanged. The pressure in the right ventricle is 15-30 mm RT. St. / O - 4 mm RT. Art.

A catheter entering the pulmonary artery is characterized by an increase in diastolic pressure and the appearance of a dicrotic rise on the pressure curve. The pressure in the pulmonary artery is normal 15-30 / 6 - 12 mm RT. st .; average pressure in the pulmonary artery 10 - 18 mm RT. Art. Further advancement of the catheter is accompanied by its entry into the distal sections of the pulmonary artery and the disappearance of the systolic component of the pulse wave. This pressure is called "jamming pressure in the pulmonary capillaries" (DZLK). After measuring the jamming pressure, the balloon is deflated; on recording equipment, this is accompanied by the appearance of a pulse pressure wave in the pulmonary artery. Normally, the indicator of jamming pressure in the pulmonary capillaries is 6-12 mm Hg. Art. This pressure corresponds to the pressure in the left atrium or the final diastolic pressure in the left ventricle (CEDAW).

This metric can be used to estimate preload. However, it should be remembered that the reliability of this indicator appears when the extension of the left ventricle remains unchanged. In addition, DZLK is equal to the hydrostatic pressure in the capillaries only when the resistance of the pulmonary veins approaches zero.
It is difficult to imagine such a situation, since the resistance of the venous part of the pulmonary circulation makes up 40% of the total resistance of the vessels of the pulmonary circle. Unfortunately, there are no direct and accessible methods for recording this indicator, therefore, the use of the DZLK indicator to characterize the hydrostatic pressure in the pulmonary capillaries requires a conditional and very careful assessment.

An increase in pressure in the pulmonary artery and DZLK can be observed with mechanical ventilation or spontaneous breathing with positive pressure at the end of exhalation (PEEP). In terminal patients on mechanical ventilation, the phenomenon of auto-PEEP may occur (as a result of incomplete exhalation). An increase in DZLK is possible with left ventricular failure, pulmonary edema, and an increase in total peripheral resistance.

Pressure reduction is possible with various types of shock, especially against hypovolemia; with collapse, the use of drugs that reduce venous tone.

Modern floating catheters are equipped with sensors that allow you to get a very important hemodynamic indicator - cardiac output. The method of thermodilution is based on the introduction of a cooled solution into the pulmonary artery and recording the temperature of the flowing blood distal to the injection site. Using special computer systems, the heat dissipation curve is recorded and the area under the obtained curve is automatically calculated with the calculation of the remaining hemodynamic parameters. The area under the curve is inversely proportional to the volumetric blood flow velocity in the pulmonary artery.

The implementation of this study requires compliance with a number of technical conditions:

1) the volume of saline or glucose should be 5-10 ml, and a decrease in this indicator will falsely overestimate the rate of cardiac output;

2) the temperature of the injected solution may correspond to room temperature;

3) the duration of administration should not exceed 4 s, if you introduce the solution slowly, you get underestimated results;

4) the introduction of the solution is preferably carried out at the end of exhalation.

Erroneous results can be obtained with intracardiac shunts and with low cardiac output. It is believed that for a reliable result, it is necessary to conduct two measurements with the calculation of the average value. Between these two indicators there should not be a difference of more than 10%. It has now been proven that, with exact adherence to the methodology, the latter is superior to dye dilution methods.

Normally, the cardiac output or minute volume of blood circulation is 4-6 l / min.

An increase in the indicator is observed with moderate hypoxia, hypercapnia, tachycardia, hyperthermia, hypermetabolism, stress, the initial stages of shock, hypervolemia.

A decrease in the indicator is noted with hypothermia, deep anesthesia, severe tachycardia (more than 1 60 per minute), shock of 3-4 degrees, acute blood loss and hypovolemia.

The volume of circulating blood (BCC) is determined by diluting various indicators (radioactive, Evans blueness, polyglucin, etc.). In this regard, the spread in the norm is from 61 to 81 ml / kg. In men of moderate nutrition, this figure is on average 70 ml / kg, in women - 60 ml / kg, with obesity, respectively - 60 ml / kg and 50 ml / kg.

To determine the bcc, you can resort to the formulas:

0,356Р + 0, ЗЗМ + 0,183 (for women),

0.367P + 0.322M + 0.604 (for men),

where P is the height in cm, M is the body weight in kg.

The volume of circulating plasma (BCP) is determined by similar methods as the bcc.

Norm: 37 - 48 ml / kg. During pregnancy, OCP increases by 40-50%.

The volume of circulating red blood cells (OEC) is normally 24 - 34 ml / kg. During pregnancy, this indicator increases by 20-30%.

An increase in BCC is observed with hyperhydration, renal failure, after taking a large amount of liquid (beer), hyperaldosteronism, increased secretion of antidiuretic hormone.

Starting from 6-8 weeks of pregnancy, the BCC begins to grow and reaches a maximum by 30 weeks, followed by stabilization before childbirth.

A decrease in BCC is possible with shocks of various origins, blood loss, exicoses, mechanical ventilation (mechanical ventilation) with moistened mixtures, the introduction of diuretics, burns of the skin, profuse sweating, diabetes mellitus (with limited access to water).

To calculate a number of hemodynamic parameters, it is necessary to know the value of the body surface area:

PPT (m?) = 0.0087 (P + MT) - 0.26;

where PPT - body surface area in m? ;

P is the growth in cm;

MT - body weight in kg.

The cardiac index (SI) represents the ratio of cardiac output to body surface area:

SI = SV / PPT [lDmin • and)]

Normally, SI is 2.5 - 3.5 [l / (min • m2)].

Impact Index (UI) - a value that characterizes the volume

blood expelled during systole from the ventricles.

MI - (SI / HR) • 1000 (ml / m?),

where heart rate is a heart rate of 1 min.

The shock work index (SDI) characterizes the work performed by each ventricle in one reduction:

IURLZH - (GARDEN - DZLK) • 0.0136 UI -0.0 IURPZH = (YES - CVP) - UI • 0.0136 (g-m2 / m2),

where L W (RV) - the left (right) ventricle,

GARDEN - mean blood pressure in mmHg. Art.,

DZLK - - jamming pressure in pulmonary capillaries in mm RT. Art.,

CVP - central venous pressure in mm RT. Art.,

DLA - the average pressure in the pulmonary artery in mm RT. st

Normally, SDI A is 44-56 g • m / m? ,

IUR ™ - 7 - 10 g • m / m? .

The vascular resistance index characterizes the resistance to blood flow in the vessels of the lungs (ISLS) and in the pulmonary circulation (IOPSS).



ISLS - [(DLA - DZLK) \ SI] • 80 [dyn • s / (cm • m?)]

IOPSS = [(GARDEN - TSVDDSI] • Normally, the value of ISLS is 80 - 240,

IOPSS - 1200 - 2500 dyn-s / (cm • m?)

Total peripheral resistance (O P S C):

OPSS (dyne / s - cm -) = (GARDEN - 79920) / SV (ml / min)

Norm: 900 - 1400 dyne / s • cm

An increase in the indicator is observed with the release of catecholamines, activation of the sympathadrenal system, hypertension, gestosis, compensated shock, the effects of cold, the effects of drugs with sympathomimetic effects, etc.

A decrease in the indicator is observed with: collapse, decompensated shock, the action of ganglion blockers and adrenolytics, deep anesthesia with fluorotan, spinal and epidural anesthesia.

Oxygen delivery (D0) is determined by the product of the cardiac SI index by the oxygen content in arterial blood (Ca0):

D02 - SI • Ca02 [mlDmin • m2)].

Normal: 520 - 720 l / min - m2.

Oxygen consumption (V0) is an indicator that characterizes oxygen consumption by tissues and their capillaries for 1 min. Defined as the product of the cardiac index

(SI) for arteriovenous oxygen difference (Ca0 - Cv0):

V02 = SI • (Ca02 - Cv02) [mlDmin - m? )].

Norm: ON - 160 l / min • m2.

The oxygen utilization coefficient (KU0) is the fraction of oxygen absorbed by the tissues from the capillary bed; it is calculated as the ratio of oxygen consumption to its delivery:

KU02 - (V02 / D02) • 100 (%).

The norm of the indicator: 22 - 32%.

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