Epidural anesthesia in childbirth

The technique of epidural space catheterization is described in many manuals; the most popular epidural anesthesia in labor is the loss of resistance technique. Lidocaine and bupivacaine can be used. Comparative studies of the use of various MA in labor have not revealed any differences in the assessment of newborns according to the Apgar scale, KOS indicators and neuropsychic status. It should be noted that the use of bupivacaine in a concentration of 0.25-0.5% can cause a high degree of motor block, which is accompanied by an increase in the frequency of application of obstetric forceps by 5 times and posterior occipital presentation by 3 times. Currently, 0.125% bupivacaine is considered the drug of choice for epidural anesthesia in labor, since in this concentration it does not have a negative effect on the dynamics of the labor act. The use of MA in low concentrations can lead to insufficient analgesia (more often in sympathotonics). The combination of MA with a central alpha-agonist (clonidine) improves the quality of analgesia and helps reduce the dose and frequency of side effects.

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Epidural anesthesia during labor in the first stage

If epidural anesthesia is performed during labor in the first stage, it is necessary to perform a sensory block at the T10-L1 level. Puncture and catheterization of the epidural space for labor pain relief is performed at the L3 level.

The duration of normal labor is 12-14 hours for primiparous women and 7-8 hours for women giving birth again. The category of pathological labor includes labor lasting more than 18 hours. Rapid labor is considered to be labor lasting from 4 to 6 hours for primiparous women and 2-4 hours for women giving birth again. Rapid labor lasts 4 hours or less for primiparous women and 2 hours or less for women giving birth again.

The first stage of labor (the period of opening) lasts 8-12 hours in primiparous women and 5-8 hours in multiparous women, begins with the appearance of regular contractions and ends with the complete opening of the cervix. The phase of slow opening of the cervix is characterized by its progressive smoothing and slow opening by 2-4 cm. The phase of rapid opening is characterized by frequent contractions (every 3-5 minutes) and rapid opening of the cervix to 10 cm. The second period (the period of expulsion) lasts from the moment of complete opening of the cervix until the birth of the child - 1-2 hours in primiparous women - from 5 minutes to 1 hour in multiparous women. The second period is divided into 2 phases. The 1st phase - from the complete opening of the cervix to the insertion of the head; the 2nd phase - from the insertion of the fetal head to its birth.

The third period (postpartum) begins from the moment of birth of the child and ends with the separation of the placenta and membranes from the walls of the uterus and their birth.

Pain in the first stage of labor is caused by contractions and the opening of the cervix. Nerve fibers transmitting these pain sensations enter the spinal cord at the level of Th10-Th12. Visceral afferents that conduct pain when labor enters the active phase reach the plexuses of the uterus and its cervix as part of the sympathetic nerves, after which they pass through the hypogastric and aortic plexuses into the spinal cord as part of the Th10-L1 roots. The appearance of pain in the perineum indicates the beginning of the expulsion of the fetus and the onset of the second stage of labor. Stretching and compression of the anatomical structures of the pelvis and perineum increase pain. Sensory innervation of the perineum is carried out by the pudendal nerve (S2-S4), therefore pain in the second stage covers the Th10-S4 dermatomes.

MA can be introduced into the epidural space only when active labor has been established!

Epidural anesthesia during labor is initiated when the cervix is 5-6 cm dilated in primiparous women and 4-5 cm dilated in multiparous women after an infusion preload of 500-1000 ml of dextrose-free solutions and a test dose (1% lidocaine or 0.25% bupivacaine 7-3-4 ml) of MA to rule out subarachnoid or intravascular placement of the catheter.

Preload: Sodium chloride, 0.9% solution, intravenously I 500-1000 ml, once.

Test dose: Bupivacaine, 0.25% solution, epidurally 3-4 ml, once or Lidocaine, 1% solution, epidurally 3-4 ml, once ± Epinephrine epidurally 15-20 mcg, once (as indicated).

Intravenous administration of drugs may cause dizziness, metallic taste in the mouth, tinnitus, tingling around the mouth. In pregnant women, the technique of test dose administration does not always prevent the anesthetic from being injected into the vessel lumen. If in a woman in labor not receiving beta-blockers, administration of MA with epinephrine (15-20 mcg) for 30-60 sec causes an increase in heart rate by 20-30/min, the catheter (needle) is in the vessel lumen. The diagnostic value of this test is not absolute, since heart rate can fluctuate significantly during contractions. The literature describes the development of bradycardia in a woman in labor after intravenous administration of 15 mcg of epinephrine. In addition, it has been proven that this dose of epinephrine reduces uterine blood flow (the degree of reduction apparently depends on the level of initial sympathicotonia) and causes distress in the fetus/newborn. In this regard, MA solutions containing epinephrine are often used only as a test dose.

Subarachnoid administration of anesthetic is accompanied by a rush of heat, numbness of the skin and weakness in the muscles of the lower extremities.

Monitoring of vital functions is performed every minute during the first 5 minutes, then every 5 minutes for 20 minutes, and finally every 15 minutes. The first dose of anesthetic is administered slowly, in fractions, 2-3 ml at intervals of 30-60 seconds until the calculated dose is achieved: Bupivacaine, 0.25% solution, epidurally 10-12 ml, once or Lidocaine, 1% solution, epidurally 10-12 ml, once ± 1 Clonidine epidurally 50-150 mcg, as indicated (usually in fractions). EA is continued according to one of the schemes: if pain occurs before the beginning of the second period, MA is administered again (10-12 ml); a continuous epidural infusion is performed with the introduction of the initial volume of anesthetic per hour, but at half the concentration (the rate of administration is adjusted depending on the effectiveness of epidural anesthesia during childbirth).

When combining MA with clonidine, the analgesic effect occurs within 15 minutes and lasts for about 3-5 hours.

Indications for epidural anesthesia:

• when other methods of pain relief are ineffective;
• women in labor with gestosis and severe hypertension;
• pregnant women with extragenital pathology;
• women in labor with DRD;
• pregnant women with multiple pregnancies and breech presentation of the fetus;
• during delivery by applying obstetric forceps.

Benefits of epidural anesthesia:

The technique is effective, predictable, rarely causes complications; and the patient is able to cooperate with medical personnel; o continuous infusion of anesthetic through a catheter maintains the woman's comfort throughout the labor; and if a cesarean section is necessary, it provides an adequate level of protection.

Advantages of continuous infusion:

• more constant level of analgesia;
• lower total dose of local anesthetic;
• less risk of developing a toxic reaction to it.

Disadvantages of continuous infusion:

• additional costs for infusion pumps;
• the need for dilution of MA;
• risk of inadvertent removal of the catheter from the epidural space and inappropriate anesthetic infusion.

Relative contraindications to epidural anesthesia:

• the patient's refusal of this type of anesthesia,
• anatomical and technical difficulties in performing the manipulation;
• neurological diseases.

Absolute contraindications to epidural anesthesia:

• lack of qualified anesthesia personnel and monitoring equipment;
• the presence of infection in the area of the proposed puncture;
• treatment with anticoagulants or bleeding disorders;
• hypovolemia (BP < 90/60 mmHg), anemia (hemoglobin < 90 g/l), antepartum hemorrhage;
• tumor at the site of the proposed puncture;
• volumetric intracranial processes;
• pronounced spinal anomalies.

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Epidural anesthesia during labor in the second stage

In the second stage, epidural anesthesia during labor should be extended to the S2-L5 dermatomes. If the epidural catheter is not installed in the first stage of labor, puncture and catheterization of the epidural space is performed in a sitting position. If the catheter was installed, the woman in labor is moved to a sitting position before the anesthetic is administered. If necessary, an infusion load is performed and a test dose of MA (3-4 ml) is administered.

If after 5 minutes there are no signs of the anesthetic entering the blood or subarachnoid space, 10-15 ml of the drug is administered at a rate of no more than 5 ml in 30 seconds:

Bupivacaine, 0.25% solution, epidural 10-15 ml, single dose or Lidocaine, 1% solution, epidural 10-15 ml, single dose.

The woman in labor is placed in a lying position with a cushion under the right or left buttock, blood pressure is measured every 2 minutes for 15 minutes, then every 5 minutes.

It should be remembered that epidural anesthesia during labor is an invasive procedure and is not without unwanted side effects and complications. An important component of safety is awareness of the possible complications of epidural anesthesia by all team members (anesthesiologist, obstetrician, and neonatologist) and their ability to prevent or promptly eliminate these complications. The woman in labor is at the center of this process: she is the only one who gives informed consent for the manipulation, and therefore the anesthesiologist and obstetrician (jointly) are obliged to provide her with objective information about the risk. Since any postpartum problems can easily be blamed on the epidural anesthesia, it is necessary to inform all those involved in the process (doctors and the woman in labor) about the real risk and problems that only coincide in time with it.

Low doses of acetylsalicylic acid taken by a pregnant woman is not a contraindication for epidural anesthesia. Prophylactic use of heparin is stopped 6 hours before epidural anesthesia, but the prothrombin time and APTT values should be normal. If the platelet count is more than 100 x 103/ml, epidural anesthesia is safe without coagulation tests. If the platelet count is 100 x 103 - 50 x 103/ml, hemostasis monitoring for DIC syndrome is necessary; in case of normal results, epidural anesthesia is not contraindicated. If the platelet count is 50 x 103/ml, epidural anesthesia is contraindicated. In addition, epidural anesthesia is not indicated in the presence of uterine scars, severe pelvic narrowing, or a giant fetus (more than 5000 g). Premature rupture of membranes is not a contraindication for epidural anesthesia unless infection is suspected.

Vaginal delivery after a lower uterine cesarean section is currently not a contraindication to RA. The idea that RA can mask pain caused by uterine rupture along the scar is considered untenable, since such rupture often occurs painlessly even in the absence of anesthesia. The most reliable symptom of uterine rupture is not pain, but changes in the tone and nature of uterine contractions.

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Problems with epidural anesthesia in labor

• difficulty (impossibility) of catheterization of the epidural space occurs in 10% of cases;
• Venipuncture occurs in approximately 3% of cases. Accidental intravascular injection of LA can lead to dangerous complications, including seizures and cardiac arrest. With the possible exception of Doppler echocardiography, all methods of identifying vascular puncture (see above) often give false-positive or false-negative results. The use of low concentrations of LA and a slow rate of administration increase the likelihood of detecting intravascular injection before catastrophic consequences develop;
• puncture of the dura mater occurs in approximately 1% of cases. About 20% of these complications are not recognized at the time of the manipulation, the danger is a total spinal block; unintentional entry of the needle or catheter into the lumen of the vessel or subarachnoid space is possible even in cases where blood or cerebrospinal fluid is not obtained during the aspiration test;
• an incomplete block occurs in 1% of cases and is caused by an insufficient dose of anesthetic, its unilateral distribution, subdural insertion of a catheter, or the presence of adhesions in the epidural space;
• Repeated manipulations are performed in approximately 5% of cases. Reasons - entering a vein, displacement of the catheter, incomplete block, puncture of the dura mater;
• toxicity from acute or cumulative overdose of LA is rare when bupivacaine is used. Early signs are dizziness and tingling around the mouth. Convulsions and circulatory arrest have been reported;
• arterial hypotension develops in approximately 5% of cases, the most likely cause is autonomic blockade against the background of ACC syndrome;
• excessive motor block is an undesirable effect of epidural anesthesia during labor, its development depends on the dose of anesthetic;
• The development of infection is rare if aseptic precautions are followed. However, isolated reports of epidural abscesses highlight the need for postnatal monitoring:
• urinary retention during childbirth is possible even without the use of epidural anesthesia;
• nausea and vomiting are not associated with epidural anesthesia;
• Back pain, contrary to popular belief, is not a complication of epidural anesthesia;
• Neonatal distress is not a consequence of properly administered epidural anesthesia, which improves placental blood flow;
• prolonged labor/increased risk of operative delivery. Properly performed epidural anesthesia does not increase the risk of operative delivery. It has been proven that early epidural anesthesia (at 3 cm dilation of the cervix) does not increase the frequency of cesarean section or instrumental delivery;
• Neurological complications are more often caused by obstetric reasons. Neurological deficits associated with epidural anesthesia include compression of the spinal cord by a hematoma or abscess (may occur spontaneously in women in labor without epidural anesthesia), damage to the spinal cord or nerve by a needle or injected air, neurotoxicity of drugs intentionally or accidentally introduced into the epidural space.

Careful assessment of the woman's condition before and after epidural anesthesia, careful performance of the manipulation are key moments in the prevention and timely correct diagnosis of complications. The absence or inadequacy of informed consent of the pregnant woman to epidural anesthesia during childbirth are frequent causes of complaints.