Anesthesia in childbirth

All women admitted to the maternity ward are potential candidates for planned or emergency anaesthesia during childbirth. In this regard, the anaesthetist must know the following minimum about each pregnant woman in the ward: age, number of pregnancies and deliveries, duration of the current pregnancy, concomitant diseases and complicating factors.

List of laboratory and instrumental examinations that should be sought in case of gestosis, including HELLP syndrome (H - hemolysis; EL - elevated liver function tests; LP - low platelet count - thrombocytopenia):

• complete blood count, including platelets, CBC, hematocrit;
• general urine analysis (assessment of proteinuria);
• hemostasiogram, including paracoagulation tests;
• total protein and its fractions, bilirubin, urea, creatinine, blood plasma glucose;
• electrolytes: sodium, potassium, chlorine, calcium, magnesium;
• ALT, AST, ALP, LDH, CPK;
• osmolality and CODpl. of blood;
• blood acid-base balance and blood gas indicators;
• determination of the presence of free hemoglobin in blood plasma;
• ECG;
• CVP monitoring as indicated.

In case of eclampsia - consultation with an ophthalmologist and neurologist, according to indications and if possible: lumbar puncture, magnetic resonance imaging of the brain and transcranial Doppler ultrasound of the cerebral vessels.

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

Premedication:

Diphenhydramine IV before induction 0.14 mg/kg, single dose
+
Atropine IV 0.01 mg/kg, single dose on the operating table or Methocinium iodide IV 0.01 mg/kg, single dose on the operating table
+
Ketoprofen IV 100 mg, single dose or Ketorolac IV 0.5 mg/kg, single dose.

What methods of anesthesia are used during childbirth?

There are non-drug and drug methods of anesthesia during childbirth.

Postulates for analgesia and anesthesia during labor:

• if the effect of a drug is unpredictable and/or the incidence of side effects is high, it is not used;
• The anesthesiologist uses the method of anesthesia (analgesia, puncture, etc.) that he is best at.

The anesthetic manual in obstetrics conditionally includes 5 sections.

The first section is anesthesia during childbirth, including breech presentation and multiple pregnancies:

• in a healthy pregnant woman with a physiological course of pregnancy;
• in a pregnant woman with extragenital pathology;
• in a pregnant woman with gestosis;
• in a pregnant woman with gestosis against the background of extragenital pathology.

It should be noted that the probability of developing abnormal labor activity (ALA) increases from the first to the last group, i.e. the number of physiological births decreases, in connection with which the following section is formed.

The second section is anesthesia during childbirth through the natural birth canal in pregnant women of the above-mentioned groups with ARDS subject to treatment, with breech presentation and multiple pregnancies.

Sometimes, in case of weak RD and/or intrauterine hypoxia of the fetus in the second period, when the possibility of a cesarean section is missed, the application of obstetric forceps is indicated, which requires anesthetic support.

ADH most often develops in pregnant women with an aggravated obstetric and gynecological history (AHA), extragenital pathology, gestosis, but can also be a consequence of improper labor management tactics. Repeated unsystematic use of uterotonics (oxytocin) can be one of the causes of discoordination of the contractile function of the uterus. An overdose of these drugs can lead to hypoxia and even death of the fetus. It should be remembered that in case of discoordination of labor activity (DLD) and AG, the use of ganglionic blockers is contraindicated, causing uterine hypotension and contributing to the development of ischemic damage to neurons of the brain in the fetus.

ARD includes:

• weakness of RD:
• primary;
• secondary;
• weakness of pushing;
• excessively strong RD;
• RD discoordination;
• discoordination;
• hypertonicity of the lower segment of the uterus;
• convulsive contractions (uterine tetany);
• cervical dystocia.

In the presence of OAG, extragenital pathology, gestosis, chronic fetal hypoxia, treatment of RD discoordination is not indicated; delivery by cesarean section is advisable. This is due to the fact that all of the above factors are life-threatening for the pregnant woman and fetus with conservative management of labor. RD discoordination predisposes to complications such as uterine rupture, amniotic fluid embolism and placental abruption, which are accompanied by hypotonic and/or coagulopathic bleeding. Gestosis in the form of preeclampsia, eclampsia and HELLP syndrome, prolapse of the umbilical cord with breech and abnormal fetal positions are indications for abdominal delivery.

Therefore, the third section of anesthesia in obstetrics will be anesthetic support for cesarean section in pregnant women of the above-mentioned groups with ARD that is not amenable or cannot be treated, breech and abnormal fetal positions, multiple pregnancies.

Such situations as manual examination of the uterine cavity, manual separation/removal of the placenta, restoration of the perineum, curettage of the uterine cavity after a late miscarriage and termination of pregnancy (fetal-destroying operations) are united by the fact that their anesthetic support does not involve the task of eliminating the harmful effects of drugs on the fetus - this is the fourth section of anesthesia in obstetrics: anesthetic support for minor obstetric operations in pregnant women (women in labor) of the above groups.

Pregnant women may require surgery for conditions unrelated to pregnancy; therefore, the fifth section of anesthesia in obstetrics will be anesthetic support for surgical interventions unrelated to pregnancy in pregnant women of the above groups.

The necessity of such gradation of initial and developing functional disorders during/as a result of pregnancy is due to the fact that they can significantly reduce the adaptive capabilities of the pregnant woman and fetus, and therefore change their response to pharmacological effects. The uniqueness of physiologically proceeding pregnancy is that it combines adaptation syndromes, since it is a physiological process, and maladaptation, since it occurs at a high level of response of vital organs and systems, not typical for a healthy adult. Consequently, the higher the degree of functional disorders in a pregnant woman, the greater the risk of complications of pregnancy, childbirth (spontaneous and surgical) and their anesthetic support due to the prevalence of the maladaptation process.

An indication for anesthesia during childbirth is severe pain against the background of established RD (regular contractions) with the opening of the cervix by 2-4 cm and the absence of contraindications (determined by the obstetrician, but the type of anesthesia during childbirth is chosen by the anesthesiologist).

An objective criterion that allows us to assess the individual pain threshold of a pregnant woman and the tactics of anesthesia during childbirth is the relationship between contractions and labor pain, on the basis of which an analgesia algorithm was constructed:

• with a very high pain threshold, pain during contractions is almost not felt and anesthesia during childbirth is not required;
• with a high pain threshold, pain is felt for 20 seconds at the height of the contraction. In the first period, the use of analgesics is indicated, in the second - intermittent inhalation of dinitrogen oxide with O2 in a ratio of 1:1;
• with a normal pain threshold, there is no pain for the first 15 seconds of the contraction, then the pain appears and lasts for 30 seconds. In the first period, the use of analgesics is also indicated, in the second - constant inhalation of dinitrogen oxide with O2 in a ratio of 1:1;
• with a low pain threshold, pain is felt throughout the entire contraction (50 sec); EA or an alternative option is indicated - intravenous administration of analgesics and tranquilizers in the first period and constant inhalation of dinitrogen oxide with O2 in a ratio of 2: 1 (control is necessary due to the risk of fetal hypoxia) - in the second.

Anesthesia during childbirth with dinitrogen oxide has not become widespread in our country for various reasons, technical capabilities and attitudes towards regional methods of analgesia and anesthesia were unstable, which did not allow for a timely large-scale assessment of their advantages and disadvantages in practice. The attitude towards the use of anxiolytics (tranquilizers) during childbirth was discussed above. In this regard, we can take only the first part from the algorithm given: determining the individual pain threshold based on the relationship between contractions and labor pain.

The second part of the algorithm - the tactics of anesthesia during childbirth requires serious improvement based on the results of recent studies assessing pregnancy from the standpoint of SIRS and placental ischemia/reperfusion syndrome. For a long time, narcotic (trimeperidine, fentanyl) and non-narcotic (metamizole sodium and other NSAIDs) analgesics administered intravenously or intramuscularly were used for anesthesia during childbirth. Recently, the issue of completely abandoning the intramuscular administration of opioids has been widely discussed. From the point of view of pharmacokinetics and pharmacodynamics, this route of administration is considered inappropriate due to its uncontrollability. The most common opioid used in our country for anesthesia during childbirth is trimeperidine. It is administered intravenously with established RD and cervical dilation of at least 2-4 cm. The use of narcotic analgesics during the latent or early active phase of labor can weaken uterine contractions. At the same time, anesthesia during labor with trimeperidine with established RD helps to eliminate its discoordination due to a decrease in the release of adrenaline. Trimeperidine administration should be stopped 3-4 hours before labor. The possibility of its use 1-3 hours before labor (in the absence of an alternative) should be agreed with a neonatologist, since T1 / 2 trimeperidine in the fetus is 16 hours, which increases the risk of CNS depression and respiratory distress in the newborn. It should be noted that opiate receptor agonists-antagonists and tramadol have no advantages over agonists, since They are also capable of depressing respiration and central nervous system function, but due to the specific mechanism of action and the state of the fetus, the degree of their suppression is unpredictable.

In this regard, EA is currently the most popular method of anesthesia during labor, as it effectively eliminates pain without affecting the consciousness of the woman in labor and the ability to cooperate with her. In addition, it reduces metabolic acidosis and hyperventilation, the release of catecholamines and other stress hormones, resulting in improved placental blood flow and fetal condition.

In order to systematize the indications for the use of various drugs and methods of their application for anesthesia during childbirth, it is necessary to build a new algorithm based not only on the assessment of pregnancy from the position of SIRS, but also on the identification of dysfunction of non-specific mechanisms of formation of the general adaptation syndrome in a pregnant woman and fetus/newborn to the process of pregnancy/childbirth. It is known that more than 70% of patients undergoing surgery are sympathotonics (dysfunction of the SAS - a non-specific trigger link in the formation of the general adaptation syndrome). Consequently, the initial state of the ANS in women before pregnancy is often characterized by sympathicotonia.

In this regard, even a physiologically proceeding pregnancy is accompanied not by a tendency to vagotonia (the norm of pregnancy), but by sympathicotonia. The presence of extragenital pathology (usually from the cardiovascular system) and/or gestosis contributes to the progression of sympathicotonia in 80% of this category of pregnant women. Pain syndrome during childbirth, especially pronounced, closes the vicious circle of the negative impact of sympathicotonia (dysfunction of the ANS) on the formation of a compensated metabolic reaction of the body of the mother and fetus (general adaptation syndrome) to the process of childbirth, transferring it to a decompensated one (complications).

In particular, excessive release of catecholamines (adrenaline) through stimulation of beta2-adrenergic receptors can reduce the frequency and strength of contractions, slowing down the labor process. Increased OPSS due to hypercatecholaminemia significantly reduces uteroplacental blood flow, which, due to hypoxia, leads to increased transplacental permeability and progression of endothelial damage. Consequently, as sympathicotonia increases, indications for the use of regional methods of analgesia/anesthesia and drugs with non-opiate analgesic activity during labor, realized through the effect on the vegetative component of pain (central alpha-adrenergic agonists) increase.

At the same time, it should be remembered that gestosis is a SVR, which, being nonspecific, is accompanied by a nonspecific ischemia/reperfusion syndrome, in this case - of the placenta. The causes of placental ischemia are disorders of trophoblast formation, endothelin synthesis in the first trimester of pregnancy, defects in the development of spiral arteries, placental hypertrophy, vascular diseases, and immune disorders. Good results of the use of calcium antagonists in gestosis are apparently associated not so much with the effect of drugs on the smooth muscles of blood vessels, but with the prevention of the calcium mechanism of cell damage (elimination of the dysfunction of the secondary messenger - calcium) and a decrease in the activity of phagocytes. The role of the calcium mechanism of cell damage is confirmed by studies that have found an increase in the intracellular calcium concentration in the endothelium of pregnant women with gestosis compared to healthy pregnant and non-pregnant women. The concentration of calcium ions in the endothelium correlated with the level of ICAM-1. Therefore, in addition to sympathicotonia, the degree of expression of the placental ischemia syndrome also determines the nature of the metabolic response of the mother and fetus/newborn to the labor process. Thus, endothelial insufficiency of the mother and vascular insufficiency of the placenta dictate the need to use drugs with non-opiate analgesic activity for anesthesia during labor, realized through increasing tissue resistance to hypoxia. Such drugs include calcium antagonists (nifedipine, nimodipine, verapamil, etc.) and, to a certain extent, beta-blockers (propranolol, etc.).

In severe gestosis (SIRS - non-specific reaction of the body), in the pathogenesis of which, in addition to dysregulation of cytokine synthesis, pain and inflammation mediators activated by the Hageman factor (hemostasis system, kinin-kallikrein, complement and indirectly - arachidonic cascade) play a major role, drugs with non-opiate analgesic activity due to inhibition of synthesis and inactivation of these mediators are indicated. Such drugs include protease inhibitors, including their synthetic analogue tranexamic acid, and NSAIDs that inhibit the synthesis of algogenic PGs. These drugs are especially effective for the prevention of clinical manifestations of the second "mediator wave" of SIRS in response to tissue damage (cesarean section, extensive tissue trauma during childbirth).

Thus, the algorithm of anesthesia during childbirth looks like this.

Anesthesia for spontaneous labor

[ 5 ], [ 6 ], [ 7 ], [ 8 ]

Intravenous analgesia

Most often, anesthesia during childbirth in healthy pregnant women with a physiological course of pregnancy is carried out using a combination of drugs from several pharmacological groups administered intravenously (scheme 1):

Trimeperidine IV 0.26 mg/kg (20-40 mg), frequency of administration is determined by clinical appropriateness
+
Diphenhydramine IV 0.13-0.26 mg/kg (up to 10-20 mg), frequency of administration is determined by clinical appropriateness
+
Atropine IV 0.006-0.01 mg/kg, single dose or Methocinium iodide IV 0.006-0.01 mg/kg, single dose.

The use of opioids in 50% of cases may be accompanied by nausea and vomiting caused by stimulation of the chemoreceptor trigger zone of the vomiting center. Narcotic analgesics inhibit gastrointestinal motility, which increases the risk of regurgitation and aspiration of gastric contents into the trachea during general anesthesia. A combination of drugs from the above groups helps prevent the development of these complications.

In the presence of contraindications to the administration of trimeperidine, the presence of initial sympathicotonia, the following anesthesia regimen during childbirth is indicated (scheme 2):

Clonidine IV 1.5-3 mcg/kg, single dose
+
Ketorolac IV 0.4 mg/kg, single dose
+
Diphenhydramine IV 0.14 mg/kg, single dose
+
Atropine IV 0.01 mg/kg, single dose. If the analgesic effect is insufficient, clonidine is additionally administered after 30-40 minutes: Clonidine IV 0.5-1 mcg/kg (but not more than 2.5-3.5 mcg/kg), single dose.

Pregnant women with initial sympathicotonia, extragenital pathology, gestosis, breech presentation and multiple pregnancy (usually diseases and complications of pregnancy accompanied by dysfunction of the ANS - sympathicotonia) in addition to the above are shown the following scheme (Scheme 3):

Trimeperidine IV 0.13-0.26 mg/kg (up to 20 mg), the frequency of administration is determined by clinical appropriateness
+
Diphenhydramine IV 0.13-0.26 mg/kg (up to 10-20 mg), the frequency of administration is determined by clinical appropriateness
+
Atropine IV 0.01 mg/kg, single dose or Methocinium iodide IV 0.01 mg/kg, single dose
+
Clonidine IV 1.5-2.5 mcg/kg (up to 0.15-0.2 mg), the frequency of administration is determined by clinical appropriateness. In case of a rigid cervix, pregnant women of all the above groups are additionally administered sodium oxybate. Our long-term experience with the use of this drug has shown that the danger of its administration to pregnant women with hypertension of any genesis (including gestosis) is incredibly exaggerated:

Sodium oxybate intravenously 15-30 mg/kg (up to 1-2 g), the frequency of administration is determined by clinical feasibility. The question may arise: what is the need to distinguish the last three groups, if the above schemes are applicable to all? The fact is that the severity and clinical significance of CNS and respiratory depression in a newborn depend on the pharmacological characteristics and doses of the drugs used, maturity and pH of fetal blood. Prematurity, hypoxia and acidosis significantly increase sensitivity to drugs that depress the central nervous system. The severity of the above disorders in the fetus depends on the presence and severity of gestosis and extragenital pathology. In addition, 10-30% of patients are not sensitive or weakly sensitive to narcotic analgesics that do not affect the vegetative component of pain. In this regard, the choice of drugs (narcotic and/or non-narcotic analgesics), doses, speed and time (until the moment of delivery) of their administration in pregnant women of these groups should be optimal (minimal, but different in the groups, which is determined by the skill and experience of the doctor). Consequently, for pregnant women with a high and normal pain threshold in the last three groups, it is more appropriate to use a combination of analgesics with a non-opiate mechanism of action in combination (according to indications) with opioids (reduced dose) and/or EA, than anesthesia during labor with trimeperidine (opioids).

Adequate anesthesia during labor accompanied by anomaly of labor activity (ALA) can accelerate the opening of the cervix by 1.5-3 times, i.e. eliminate ALA due to a decrease in the release of catecholamines and normalization of uterine blood flow. In this regard, the principles (methods) of anesthesia during labor (with an emphasis on epidural anesthesia), outlined above, remain relevant for this category of pregnant women.

Depending on the degree of sympathicotonia and placental insufficiency (gestosis), preference is given to methods that include clonidine, beta-blockers and calcium antagonists. It is impossible to draw a clear line between anesthesia during childbirth and ARD therapy in this category of pregnant women. The tasks of the manual do not include a description of ARD treatment methods (this is an obstetric problem that is solved in maternity hospitals with a high level of pharmacorationality by developing a comprehensive obstetric-anesthesiological-neonatal care).

Anesthesia in childbirth and calcium antagonists

It is known that calcium antagonists have anti-ischemic, tocolytic, moderate analgesic, sedative and weak myoplegic properties.

Indications for the use of calcium antagonists:

• premature birth;
• excessively strong labor activity - in order to reduce hypertonicity of the myometrium;
• hypertensive form of weak labor activity - with the aim of normalizing the increased basal tone of the uterus;
• DRD (irregular contractions, disturbances in their rhythm) - to normalize the tone of the uterus;
• intrauterine fetal hypoxia caused by ARD - intrauterine resuscitation;
• preparation for childbirth in the absence of biological readiness and a pathological preliminary period.

Contraindications to the use of calcium antagonists:

• for all calcium antagonists - arterial hypotension;
• for verapamil and diltiazem - sick sinus syndrome, grades II and III AV block, severe LV dysfunction, WPW syndrome with antegrade impulse conduction along additional pathways;
• for dihydropyridine derivatives - severe aortic stenosis and obstructive form of hypertrophic cardiomyopathy.

Caution is required when using these drugs during treatment with prazosin, euphyllin, magnesium sulfate, beta-blockers, especially when administered intravenously. Inclusion of nifedipine or riodipine in the above-mentioned regimens in healthy pregnant women, pregnant women with gestosis, with a hypokinetic type of hemodynamics, in addition to enhancing analgesia, is accompanied by an increase in the stroke index, SI and a decrease in TPR (in the absence of hypovolemia), favorable changes in cardiotocographic parameters of the fetus, which allows us to regard the use of drugs as intranatal protection from hypoxia: Nifedipine sublingually, transbucally or orally up to 30-40 mg per delivery, the frequency of administration is determined by clinical appropriateness, or Riodipine orally 30-40 mg per delivery, the frequency of administration is determined by clinical appropriateness.

Pregnant women with hyper- and eukinetic types of hemodynamics are recommended to use verapamil or propranolol depending on the type of ARD.

Verapamil is administered intravenously by drip or through an infusion pump, depending on the purpose and the result obtained (after achieving tocolysis, the administration is usually stopped):

Verapamil intravenously by drip 2.5-10 mg or through an infusion pump at a rate of 2.5-5 mg/h, the duration of therapy is determined by clinical appropriateness.

Calcium ions in the cytoplasm of cells initiate processes that lead to fetal brain damage during reoxygenation after hypoxia due to activation of glutamate and aspartate release, proteases, phospholipase and lipoxygenase. In this regard, pharmacological prevention of post-hypoxic brain damage in the fetus, which develops under conditions of placental insufficiency, should include the use of calcium antagonists.

[ 9 ], [ 10 ], [ 11 ], [ 12 ], [ 13 ], [ 14 ]

Anesthesia in childbirth and beta blockers

Propranolol (beta-blocker) potentiates the effect of narcotic and non-narcotic analgesics, anesthetics, eliminates the feeling of fear, tension, has anti-stress and labor-activating effects, increases the degree of neurovegetative inhibition (NVI) during anesthesia. The labor-activating effect of propranolol is due to the blockade of beta-adrenergic receptors of the uterus and an increase in the sensitivity of alpha-adrenergic receptors to mediators (norepinephrine) and uterotonics. The drug is prescribed sublingually (it is necessary to warn about the local anesthetic effect of the drug) after intravenous administration of atropine, diphenhydramine and ketorolac (schemes 1 and 2; in case of severe pain syndrome, in combination with trimeperidine - no more than 2/3 of the specified dose) in combination with calcium chloride, if the task is to treat DRD:

Propranolol sublingually 20-40 mg (0.4-0.6 mg/kg)
+
Calcium chloride, 10% solution, intravenously 2-6 mg.

If necessary, this dose of propranolol can be repeated twice at an interval of one hour if the obstetrician sees insufficient effect of treatment of DRD.

Contraindications to the use of beta-blockers include bronchial asthma, COPD, grade II-III circulatory failure, fetal bradycardia, excessively strong labor, lower segment hypertonicity, and uterine tetany.

If labor lasts 18 hours or more, the energy resources of the uterus and the pregnant woman's body are exhausted. If during these 18 hours a picture of primary weakness of labor activity is observed and the possibility of labor ending in the next 2-3 hours is completely excluded (determined by the obstetrician), it is indicated to provide the woman in labor with drug-induced sleep-rest. Anesthetic assistance is provided according to one of the above schemes, but with the obligatory use of sodium oxybate:

Sodium oxybate intravenously 30-40 mg/kg (2-3 g).

In the presence of absolute contraindications to its use, Droperidol is used: Droperidol intravenously 2.5-5 mg.

In case of secondary weakness of labor activity, the tactics of the anesthesiologist are similar, but the drug-induced sleep-rest should be shorter. In this regard, the dose of sodium oxybate is reduced.

Sodium oxybate intravenously 20-30 mg/kg I (1-2 g).

If it is necessary to apply obstetric forceps, the following can be used: intravenous anesthesia based on ketamine or hexobarbital; intravenous anesthesia during childbirth based on ketamine or hexobarbital

[ 15 ], [ 16 ], [ 17 ], [ 18 ], [ 19 ]

Induction and maintenance of anesthesia during labor:

Ketamine IV 1 mg/kg, single dose or Hexobarbital IV 4-5 mg/kg, single dose
±
Clonidine IV 1.5-2.5 mg/kg, single dose.

Ketamine is administered after premedication at a rate of 1 mg/kg, if necessary in combination with clonidine (the analgesic effect of clonidine develops 5-10 minutes after intravenous administration).

During intravenous anesthesia during childbirth, short-term relaxation of the uterus can also be achieved by administering nitroglycerin (intravenously, sublingually or intranasally), provided that hypovolemia is eliminated.

Inhalation anesthesia during childbirth

In women in labor with gestosis, ketamine is replaced by hexenal or mask anesthesia is performed (halothane or better analogues - short-term for relaxation of the uterus, dinitrogen oxide, oxygen):

Dinitrogen oxide with oxygen by inhalation (2:1,1:1)
+
Halothane by inhalation up to 1.5 MAC.

Retonar anesthesia during childbirth

If epidural anesthesia is administered during childbirth, there is no problem with the application of obstetric forceps.

The method of choice is also CA, covering segments T10-S5:

Bupivacaine, 0.75% solution (hyperbaric solution), subarachnoid 5-7.5 mg, single dose or Lidocaine, 5% solution (hyperbaric solution), subarachnoid 25-50 mg, single dose.

Advantages:

• ease of implementation and control - the appearance of CSF;
• rapid development of the effect;
• low risk of toxic effects of the anesthetic on the cardiovascular system and central nervous system;
• does not have a depressing effect on the contractile activity of the uterus and the condition of the fetus (while maintaining stable hemodynamics);
• Spinal analgesia is cheaper than epidural and general anesthesia.

Flaws:

• arterial hypotension (relieved by rapid infusion and intravenous administration of ephedrine);
• limited duration (the presence of special thin catheters solves the problem);
• post-dural puncture headache (the use of smaller diameter needles significantly reduced the incidence of this complication).

Necessary:

• monitoring the adequacy of spontaneous breathing and hemodynamics,
• full readiness to transfer the patient to mechanical ventilation and conduct corrective therapy.