Cardiotocography in childbirth

It was established that cardiac activity of the fetus in the I period, delivery in the absence of hypoxia is not subject to significant changes and the heart rate averages 120-160 beats / minute. Does not affect it, according to the authors, and autopsy of the bladder.

In the II period of labor, more dangerous situations can be created. GM Savelieva et al. (1978) believe that in cardiomonitor observation, the criteria for the initial and expressed signs of fetal hypoxia are different in the first and second periods of labor. In the first period, the authors attribute bradycardia to 100 beats / min and tachycardia no more than 180 beats per minute to the initial signs of hypoxia, as well as periodically arising monotonicity of the rhythm and short-term late contractions of the heart rate. In the second stage of labor, the initial signs of fetal hypoxia are bradycardia (90-110 beats / min), arrhythmias, late and Y-shaped contractions of the heart rate outside the contraction.

In labor during the analysis of cardiotocogram (CTG), three parameters should be systematically taken into account: the basal rate of fetal heart rate, variability of the basal line and deviations associated with uterine contractions. Deceleration is the most important parameter of the fetal condition. They are determined in the form of a reduction in the basal frequency of the cardiotocogram, are associated with uterine contractions and should be differentiated with bradycardia, manifested simply in the form of a decrease in the basal level of the cardiotocogram without uterine contractions. When assessing the condition of the fetus, it is extremely important to determine the time relationship between uterine contractions and de-erythoras.

At present, throughout the world, the greatest distribution in the scientific and practical activities of obstetricians has been the three classifications of decleration:

• classification of Caldeiro-Barcia (1965);
• classification Hona (1967);
• classification of Syuro (1970).

Classification of Caldeiro-Barcia. In chronological comparison of temporal phases of uterine contraction with the onset, duration and end of fetal declerosis, the three most typical variants of the curves were identified. There are two types of deceleration: dip I and dip II. According to the classification of Caldeiro-Barcia, deceleration is the time ratio between the lowest point of deceleration and the top of the corresponding uterine contraction.

At the first type in the near future after the onset of contraction, a slowing of the fetal heart rate is observed, which quickly passes, with the cessation of contraction, the fetal heart rate is normalized (dip I). Deceleration of this type usually lasts no more than 90 seconds and the heart rate does not fall below 100 beats per minute.

In the second type, the fetal decleresis begins 30-50 s after the peak of the contraction and lasts for some time after the contraction is over (dip II). At the same time, the fetal heart rate is rarely less than 120 beats per minute. Very rarely, deceleration can be deeper - up to 60 beats / min or less. The duration of such a deceleration usually also does not exceed 90 s. In such cases, after the end of the contraction, a so-called compensatory tachycardia is possible. This type of decleration is often combined with acidosis in the fetus.

Classification of Hon. In this classification, two main criteria are taken into account: the relationship between the onset of contraction and the onset of deceleration and its form. Hon distinguishes three types of decleration:

• Early de-erserations begin with a uterine contraction and have a regular shape. These decelerations are now considered as physiological due to compression of the fetal head;
• late decelerations begin 30-50 s after the beginning of uterine contraction and also have the correct form. They are due to fetal hypoxia;
• Variable decelerations are characterized by a different time of occurrence relative to the onset of uterine contraction and are a combination of the first two types of decleration. At the same time, they are variable in form, and also in relation to one deceleration to another. In addition, they are also different with respect to uterine contractions. The emergence of such a deceration is associated with the compression of the umbilical cord. If the cord is compressed for a short time, it does not have a damaging effect on the fetus. Prolonged compression of the umbilical cord or a significant increase in intrauterine pressure may have a damaging effect on the fetus. Variable decelerations can be observed in the syndrome of the inferior vena cava.

Classification Syuro. There are 3 types of deceleration: simultaneous deceleration, residual deceleration and the amplitude of deceleration.

With simultaneous de-cessation, the end of the bout coincides with the end of the deceleration.

Residual deceration is characterized by the fact that after the end of the bout there remains the so-called residual deceleration.

The amplitude of the deceleration is the amplitude of the deceleration with respect to the basal level.

There are three types of amplitude of deceleration: moderate, threatened and dangerous.

For simultaneous deceleration, the moderate amplitude is within 30 bpm, the threatening amplitude is up to 60 beats / min, if more - the amplitude is dangerous.

For residual deceleration, the moderate amplitude is already within 10 bpm, threatening amplitude - up to 30 bpm, and 30-60 bpm is regarded as a dangerous amplitude.

Classification Syuro is based on the following principles:

• all decelerations must be taken into account;
• deceleration should be considered the most informative if they have the form of late deceleration or are prolonged with respect to uterine contraction;
• the danger to the fetus increases with an increase in the deceleration amplitude (this pattern is established for both late and variable decelerations);
• there is still considerable disagreement about the pathophysiological origin of deceleration, so first of all it is necessary to know their prognostic value, and there are data on the compression of the umbilical cord, then the obstetrician should regard this type of decleration as a hazard to the fetus.

Based on the data presented, it is advisable to monitor the following at high risk mothers and in the choice of the most rational method of delivery, especially when deciding on abdominal delivery:

• if there is a meconium admixture in the amniotic fluid and good CTH indices of the fetus, there is no need for urgent surgical intervention;
• less severe types of decleration are often difficult to interpret, but the addition of the pH value of capillary blood from the fetal head skin in combination with the CTG monitor definition allows one to determine the degree of its suffering;
• various variants of deviations on the cardiotocogram are the earliest indication indicating the possibility of fetal suffering, but a change in pH is a more accurate indicator of his condition. Therefore, when the pH figures from the skin of the fetal head are normal, even in the presence of pathological CTG, caesarean section operations can be avoided.

In accordance with the classification of Syuro recommend four options for the management of pregnant and parturient women.

I. Norm or moderate amplitude of decelerations:

A) norm:

• basal line of CTG - 120-160 beats / min;
• variability of the curve - 5-25 beats / min;
• there are no decelerations.

B) moderate amplitude of decelerations:

• basal line of CTG - 160-180 beats / min;
• variability of the curve - more than 25 beats / min;
• simultaneous decelerations - less than 30 beats / min, residual - less than 10 beats / min;
• an acceleration.

II. Threatened state for a human being:

• basal line of CTG - more than 180 beats / min;
• the variability of the curve is less than 5 bpm;
• simultaneous decelerations - 30-60 beats / min, residual - 10-30 beats / min.

III. Oat condition for fetus:

• several threatening signs on CTG;
• basal line - less than 100 beats / min;
• simultaneous decelerations - more than 60 beats / min, residual - more than 30 beats / min.

IV. Extreme condition of the fetus:

• tachycardia in combination with flattened CTG curve and residual deceleration;
• residual decelerations - more than 60 beats / min longer than 3 minutes.

At the first variant the woman in the process of labor does not need any interventions.

The second variant does not exclude the birth through natural birth canals, but if possible, a Zanding test should be performed to determine the pH of the capillary blood from the skin of the fetal head. Taking into account the obstetrical situation, it is advisable to carry out the following measures: to change the position of the parturient woman, laying it on its side, to decrease the uterine activity, to carry out oxygen inhalations and to treat maternal hypotension. If these measures are ineffective, appropriate preparation for the caesarean section should be carried out.

In the third variant, the same treatment measures and diagnostic methods are carried out.

The fourth option requires immediate delivery.

When carrying out the Zaling test, it is necessary to take into account not only the values of the actual pH, but also the time of repeated samples: the pH value greater than 7.25 should be regarded as an indicator of the normal state of the fetus; pH values within 7.20-7.25 indicate a threatening condition of the fetus and re-determination of the pH should be made no later than 20 minutes after the first Zaling test; at the actual pH less than 7.20, a second analysis is performed immediately, and if there is no tendency to increase these parameters, a caesarean section should be performed.

At the moment there is no one objective method on the basis of which it is possible to accurately determine the degree of suffering of the fetus, as well as to resolve the issue of operative delivery.

Computer evaluation of cardiotocograms in childbirth

At present, some countries have developed programs for computer evaluation of intranatal CTG. Some programs also include analysis of uterine activity, which is of great importance in the administration of oxytocytics in childbirth.

E. A. Chernukha and co-authors. (1991) developed a computerized CTG score in childbirth. Multifactor analysis of CTG involves the inclusion in the discriminant equation of the main parameters of cardiac fetal activity and uterine activity.

Based on the aggregate of computer data at intervals of 2-3 min gives out conclusions about the state of the fetus:

• from 0 to 60 conv. UE - normal fetal condition;
• from 60 to 100 conv. Units - border crossing point;
• above 100 usl. Units - severe fetal suffering.

At the borderline of the fetus, the display reads "Identify the fetus". After the introduction of the mother of appropriate drugs, the inscription disappears. However, with the progressive deterioration of the fetus, a directive "Take into account the possibility of termination of labor" appears. The computer only ascertains a significant deterioration of the fetus, requiring emergency measures, but the scope of the activities is entirely determined by the doctor who leads the delivery. Ute activity is counted by a computer in units of Montevideo. At a level below 150 EM for 45 minutes there is an opinion on reduced uterine activity, and after 10 minutes - an indication of the need to appoint uterotonic drugs. At the level of uterine activity above 300 EM after 20 minutes, the inscription "Increased uterine activity" appears, and after 10 min (ie, 30 min after exceeding the standards of uterine activity) - "Tokoliz".

[1], [2], [3], [4]