The technique of vacuum hypothermic-extraction of the fetus

Apparatus "Vacuum-gnpoterm-extractor". The developed apparatus and the technique of its use allow carrying out craniocerebral hypothermia of the fetus during childbirth and at the same time, in view of the technical innovations of the device, it is most gentle to perform the delivery by means of the vacuum extraction operation against hypothermia of the fetus. The device consists of an elastic hood, connected with a vacuum unit and a refrigeration unit; sensors from the vacuum hypothermic extractor are connected to the encephalograph and potentiometer. In the thickness of the walls of the hood parallel to the base, channels are channeled annularly and over the entire surface, connected to a source of refrigerant under pressure. This design allows the vacuum extractor to give the hypothermic function (hypothermia refers to special suits, helmets, refrigerators and other equipment designed for hypothermia), and quickly and securely fix the cap to the fetal head, due to its automatic opening in the birth canal. Throughout the operation it is possible to obtain information about the functional state of the fetus (registration of direct ECG, EEG, REG) and the rate of lowering the temperature of its brain, in view of the built-in sensors. The design of the device (due to the contact of the cooled cap and the cooled tubes, through which the coolant enters, along the walls of the vagina) allows simultaneous hypothermia of the vagina and thus influence the contractile activity of the uterus (this issue is not considered in this work).

The refrigerating unit ALG-2 m, to which the vacuum hypothermic extractor is connected, allows rapid cooling of the circulating solution and automatically maintains the solution temperature in the range of -5 to -7 ° C.

Along with the use of an elastic cap, metal cups with a cooling system are used for vacuum extraction with simultaneous craniocerebral hypothermia, while the circulation of cooled liquid occurs between the double walls of the cup, with built-in electrodes for recording ECG, EEG, REG and thermocouple. Preparing the woman in labor for the operation is not different from other obstetric operations - it is necessary to empty the bladder and intestines, treat the external genitalia and thighs with alcohol and 2% iodine solution, and close the operating field with sterile underwear.

Often when the fetus is vacuum-extracted, the AVE-1 standard vacuum extractor detaches the cup from the fetal head - this is often due to the insufficient adhesion force between the cup and the head. The traction force that a midwife can develop is equal and opposite in direction to the force of adhesion between the cup and the head. This traction force is calculated by the formula proposed by Malmstrom. According to this formula, for the Malmstrom-type cup No. 7, with a diameter of 60 mm, at a negative pressure of 0.8 kg / cm ^{2, the} maximum traction force will be 22.6 kg. The traction force developed by the obstetrician was tried to be determined by a dynamometer and expressed approximately 25 kg. With this traction force, there is no guarantee that the cup will not slide off the fetal head.

The traction force can be increased in two ways: by increasing the negative pressure under the cup-cap or by increasing the area of the cup touching the head (working surface). It is impossible to increase the negative pressure above 0.7-0.8 atm, as this will lead to a deep trauma of the skull and the brain of the fetus. An increase in the working surface of metal cups above No. 7 (diameter 60 mm) is also not possible. In the construction of the same vacuum-hypothermic extractor with an elastic cap, which can be inserted into the birth canals in the folded form, it is possible to increase the working surface - respectively, increases the adhesion force. The risk of tearing off the hood during traction is significantly reduced. According to the Malmstrom formula, the maximum tractive force, and therefore the adhesion force, taking into account the diameter of the elastic cap, equal to 10 cm, with an air pressure of 0.8 atm will be 62.8 kg.

Consequently, the maximum traction force when applying the vacuum-hypotherm extractor proposed by us can be increased almost 3-fold, although there is no need for this, but it should be noted that the risk of tearing off the hood during traction is also reduced by almost 3 times. Snoeck, Dragotesku, Roman conducted a thorough study of the mechanical foundations of the vacuum extraction method and the imposition of obstetric forceps on the contents of the fetal skull. The authors showed that the traction intracranial pressure during fetal vacuum extraction reaches 75 g / cm ², and in the case of even the most successful forceps - 1480-1500 g / cm ², ie, the pressure on the brain during vacuum extraction.. , even under less favorable conditions, is only 1/2 part of the pressure when applying obstetric forceps.

When using the elastic vacuum-hypothermic extractor we proposed, the area of contact with the fetal head increases almost 2-fold, the distribution of negative pressure during traction occurs on twice the increased area, and therefore intracranial pressure in the fetus during tractions is only 35-40 g / cm ².

Vacuum hypothermic extractor with an elastic cap was used by us, mainly when the fetal head is located in the cavity or in the exit of the small pelvis.

Indications for the application of the vacuum hypothermic extractor:

• weakness of labor, threatening fetal asphyxia;
• started intra-natal fetal asphyxia;
• toxicosis II half of pregnancy, the threat of intrapartum asphyxia of the fetus;
• a narrow pelvis, incorrect head presentations, a long standing of the head in one plane of the small pelvis;
• extragenital pathology;
• premature detachment of the anterior placenta;
• prolapse of the umbilical cord (after its correction).

Contraindications to the use of vacuum hypothermic extractor:

• a clinically narrow pelvis excluding the possibility of delivery through natural birth canals;
• central placenta previa:
• facial and frontal presentation;
• hydrocephalus;
• deep prematurity of the fetus.

Conditions for the use of vacuum hypothermic extractor.

A necessary condition for the application of the vacuum hypothermic extractor is the absence of a fetal bladder, the opening of the cervix at least 6 cm, which is sufficient to introduce a cup-cap with a fixed head.

The technique of vacuum extraction with simultaneous craniocerebral fetal hypothermia

The mother is placed on the operating table or Rachman's bed in a position generally accepted for vaginal manipulation. After the appropriate preparation of the external genitalia, the vagina is opened with mirrors (the vacuum-hypothermic-extractor cap capping is permissible and under the control of the fingers), the sterilized cup cap is applied to the fetal head, closer to the wire point. With the help of a manual or electric pump under the hood, attached to the head of the fetus, air is discharged to 0.1-0.2 atm in order to fix it to the head of the fetus. After that, the mirrors are removed. Then, the circulation of the cooled liquid is turned on - the temperature of the hypothermic surface drops to -5 ° C and is automatically maintained at this level.

Moderate cranio-cerebral hypothermia of the fetus, at which the temperature of the skin of the fetal head under the cap of the vacuum hypothermic extractor decreases to +27 - + 28 ° C (the temperature at the level of the fetal cortex is + 29 - + 30 ° C) is achieved with this mode for 20-30 minutes. After reaching a moderate hypothermia in the presence of indications for vacuum extraction of the fetus, the air under the cap is pumped to 0.5-0.7 atm (pumping out the air must be done slowly (!) For 3-5 minutes) and conduct the traction itself in conjunction with contractions or attempts. Throughout the operation, dynamic control over the functional state of the fetus is advisable (cardiac monitoring, ECG, EEG, Fetal regurgitation, etc.).

Due to the therapeutic effect of hypothermia on the fetus under hypoxic conditions, increasing the resistance of its brain to extreme conditions and stabilizing or improving its functional state, the time interval for vacuum extraction against the background of craniocerebral fetal hypothermia expands, ie, the obstetrician wins time , so do not force the operation, but, following the functional state of the fetus, carefully, with small force tractions, produce vacuum-extraction on the background of hypothermia of the fetus. When the head is erupted, the vacuum in the vacuum-hypothermic extractor system is eliminated and the cap removed from the head. The average time of operation of vacuum extraction with simultaneous craniocerebral fetal hypothermia is 30-40 min, whereas the time of usual vacuum extraction is 15-20 min on average. Consequently, the technique of vacuum-extraction against the background of craniocerebral fetal hypothermia consists of two moments.

The first point we called: "vacuum hypothermia of the fetus", when only craniocerebral fetal hypothermia is carried out (the vacuum-hypothermic extractor cup is fixed by a harmless vacuum of 0.1-0.2 atm to the fetal head), with no traction.

The second point is the tract itself on the background of hypothermia of the fetus (air discharge under the vacuum-hypothermic extractor cup is brought to 0.5-0.7 atm).

The whole operation, consisting of the first and second moments, we gave the name - "vacuum hypothermic-extraction of the fetus." The first moment takes, on average, 20-30 minutes, while the second takes 10-20 minutes. The whole operation takes an average of 30-40 minutes.

In conclusion, the following should be noted:

1. The temperature of the skin of the fetal head under the hood during a hypothermia session is measured with a thermocouple mounted in the cap. The preset temperature of the head skin (+ 27 ° - + 28 ° C) with the help of the relay is maintained at this level by switching on and off the refrigerant circulation. In view of the fact that the recovery of the temperature of the brain after the termination of hypothermia is slow (up to 48 hours), there is practically no need for a repeated vacuum-hypothermia session until the completion of labor.
2. With complicated delivery and development of intrapartum asphyxia of the fetus, after the first moment of the operation (maximum vacuum hypothermia time - 1.5 h), proceed to the completion of labor. If conditions exist, then vacuum-extraction is carried out against the background of hypothermia of the fetus or completed by the application of obstetric forceps, depending on the indications. If the cervix of the uterus has not fully opened, then the birth is accelerated as by medication, so. And the use of vacuum stimulation of the fetus.
3. The maximum time of craniocerebral hypothermia of the fetus followed by vacuum extraction on its background (i.e., the 1st and 2nd moment of the operation) is 2 hours. The exposure of the vacuum hypothermic extractor cap to the head of the intrauterine fetus, at the coolant temperature and accordingly surfaces - 5 ° С, over 2 hours negative consequences are possible. A vacuum of 0.1-0.2 atm, fixing the cup-cup for a given time, is harmless, but cooling itself for more than 2 hours can lead to necrosis of skin areas and to the transition of hypothermia from the stage of the moderate to the deep stage, which is undesirable.
4. In the event of impairment of the functional state of the fetus (usually associated with the underlying pathology) during the operation, immediately begin the completion of labor.
5. It is not necessary to bring the air discharge under the cup-cap above 0.1-0.2 atm in the vacuum-hypothermia session, i.e., at the 1st moment of the operation, and more than 0.5-0.7 atm with tractions on the background of hypothermia fetus, i.e. At the 2nd, because forced traction is not carried out, the obstetrician, having a time reserve, extracts the fetal head with careful tracts, less injuring the fetus as well as the birth canal.