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Introduction
Norepinephrine is released through descending inhibitory pathways that terminate in the dorsal gray matter of the spinal cord (Figure 1.8). Muscarinic (cholinergic) receptors are found in the gray matter of the dorsal horn of the spinal cord.
Pulmonary
Alkalosis will also shift the hemoglobin-oxygen dissociation curve to the left, reducing the release of O 2 to the fetus.
Gastrointestinal
Renal
The renal tubules are probably unable to accommodate the increased filtered glucose load that accompanies the increase in GFR.
Hepatic and Gallbladder
Thyroid
Hematologic
Glucose Metabolism
Neurologic
Uterus
Prior to placement of the epidural catheter or induction of epidural analgesia for labor, a focused history and physical examination should be performed. The double Lidocaine test dose is recommended to test the adequacy of the epidural catheter in patients at high risk of needing a caesarean section.
Medications
Cardiotoxicity depends on the specific drug, the total dose administered and the concentration of the local anesthetic agent in the blood. The addition of fentanyl 2 mcg/ml to dilute local anesthetic concentrations (usually bupivacaine for analgesia during labor) reduces local anesthetic use by 25%–30.
Combined Spinal Epidural (CSE) Analgesia
Once the epidural space is located with the epidural needle, the spinal needle is inserted through the lumen of the epidural needle. It is recommended that the spinal needle tip extend 11–15 mm beyond the tip of the epidural needle to facilitate dural puncture. The tip of the spinal needle in the photo extends 11 mm beyond the tip of the epidural needle.
Further advancement of the epidural needle may result in the dura returning over both the spinal and epidural needle tips, causing an inadvertent "wet tap" with the epidural needle.
Continuous Spinal Analgesia
Accidental dural puncture in parturients approaching delivery. multiparous women presenting in late stage labour). Continuous spinal anesthesia can reduce the likelihood of a high spinal block from a one-shot spinal technique by allowing for careful titration of the anesthetic to a desired sensory dermatomal level. With the intermittent bolus technique, the catheter must be flushed after each injection with a 2 ml bolus, as the epidural catheter and filter can contain up to 1 ml of dead space.
Epidural catheter and filter have > 1 ml dead space; therefore, the continuous spinal catheter should be flushed with 2 mL of saline after each bolus dose.
Alternative Regional Anesthetic Techniques
This technique produces analgesia of the lower uterine segment, cervix, and upper vaginal canal by anesthetizing the paracervical ganglion (Frankenhauser). Maternal toxicity results from systemic absorption or direct intravascular injection, while fetal bradycardia results from direct absorption, vasoconstriction of the uterine arteries, or from accidental injection of local anesthetic into the fetal part. In addition, hematomas of the broad ligament and retrosoal or subgluteal abscesses have been reported.
Disadvantages include the risk of systemic toxicity from intravascular injection, possible trauma to the pudendal artery or the presenting part of the fetus, the formation of vaginal wall hematomas and retropsoas or subgluteal abscesses.
Improving Anesthetic Effi ciency in Obstetrics
This technique blocks the nerve roots S 2 –S 4 and the pain coming from the perineum, the lower vaginal wall and the vulva. Perineal infiltration is the most commonly used regional anesthesia technique in patients delivering without pre-existing epidural analgesia. Because the perineum has no major nerves, local anesthetic must be injected subcutaneously and submucosally to achieve anesthesia.
Multiport epidural catheters reduce the incidence of inadequate analgesia and the number of catheters requiring manipulation compared to single port epidural catheters.
Epidural Analgesia and the Progress of Labor
Despite the justified enthusiasm of obstetric anesthetists for epidural analgesia, pain during labor and delivery is contextually unique and individual-specific. For example, transcutaneous electrical nerve stimulation (TENS; Figure 3.4) and "water blocks". Figure 3.5 ) appears more commonly in Scandinavia; ketamine in india;. Nitrous oxide was described as an analgesic for labor pains in 1880, and became popular after the manufacture of the Minnitt apparatus for self-inhalation of mixtures with air.
Morphine and scopolamine injection were introduced in 1902 for labor pain, but little systematic evaluation of the neonatal effects was attempted until Virginia Apgar developed her simple scoring system in 1953.
What to Tell the Woman
The 1982–1984 report of the Confidential Inquiries into Maternal Deaths in the United Kingdom recommended greater use of regional anesthesia, which is now used in the vast majority of elective and non-elective caesarean sections in developed countries. The period 1997-2002 shows that the mortality rate with general anesthesia is twice as high as with regional anesthesia, although the figures for all types of anesthesia, especially general anesthesia, have decreased. Maternal mortality in the UK and the Confidential Inquiries into Maternal and Child Health (CEMACH) also indicate far fewer deaths due to regional anaesthesia.
Obtaining Consent for Anesthesia
The American College of Obstetricians and Gynecologists (ACOG) suggests that when risk factors are identified, “the obstetrician obtains antepartum consultation with an anesthesiologist” and that strategies such as early intravenous access and placement of an epidural or epidural tube are employed. Drug or solution should not be injected due to the risk of intraneural injection and disruption, which may lead to injury. This is especially important when an emergency caesarean section (category 1) carries a significant risk (e.g. in women with a fetal condition during labor) or when general anesthesia is a major concern (e.g. in morbidly obese women or a patient with a difficult labor ). respiratory tract).
If the entry of the epidural needle into the epidural space is not in the midline, the spinal needle may not enter or remain in the subarachnoid space (Figure 4.7.
Continuous Spinal Anesthesia
Especially in developing countries, some obstetricians are gaining experience in performing caesarean sections under progressive local anesthetic infiltration of the abdominal wall (Figure 4.8), with or without instillation of local anesthetic into the peritoneal cavity and wound, or field block of the lower abdomen (bilateral iliohypogastric and ilioinguinal nerve blocks). This is thought to be the result of irritation of the subdiaphragmatic peritoneum by blood and amniotic fluid. Shoulder point pain can be reduced by tilting the head on the table and sometimes counter-irritation, with vigorous rubbing of the painful shoulder.
Some like to keep agents for induction and intubation of the patient (eg, sodium thiopental and succinylcholine) on hand.
Management of Early Complications of Regional Anesthesia
Medications can be inadvertently injected into the wrong space (for example, subarachnoid injection of epidural solution through a catheter that is assumed to be entirely in the epidural space). Increasing sensory and motor blockade resulting in dyspnea or apnea (at any time .. within 30 minutes of spinal injection, sometimes associated with a change in patient posture). Regional anesthesia can reduce blood loss, and in many cases clinical experience supports starting with a regional technique, but keeping the threshold low for conversion to general anesthesia in case of major bleeding.
Although fetal oxygen tension in the umbilical vein and arteries increases with oxygen and higher oxygen inspired by the mother (Figure 4.14), this confers no apparent benefit to the healthy newborn.
Management of Complications of General Anesthesia
There is evidence that the incidence of the latter is falling, and epidemiological data show that general anesthesia for caesarean section can be exceptionally safe. A number of practice guidelines (eg the ASA) exist for non-obstetric patients, but are not specific for obstetric patients and situations, which are complicated by considerations relating to the fetus. Obstetric anesthesia149. pressure, pressure to the right or higher on the thyroid cartilage) and release it completely if necessary - the first priority is effective ventilation and oxygenation.
This should be specifically discussed when obtaining consent for general anesthesia for caesarean section.
Informing the Patient
As the dose of epidural morphine increases from 0 to 5 mg, the use of self-administered PCA morphine for adjunctive analgesia decreases until the dose reaches approximately 4 mg. Epidural morphine can cause nausea and vomiting by stimulating the chemoreceptor trigger zone located at the base of the brain's fourth ventricle. Such reports indicate that the incidence of clinically significant respiratory depression following epidural morphine (at doses of 5 mg or less) in the obstetric population is highest.
Like fentanyl, the major advantage of epidural sufentanil over epidural morphine is its rapid onset.
Continuous Intrathecal Analgesia
Obstetric Anesthesia175 doses above 0.2 mg) and 10-15 mcg of fentanyl with lidocaine or bupivacaine remains the best choice of postoperative analgesics. This could be IV-PCA morphine, but since many pregnant women are able to tolerate oral analgesics within hours of their surgery, oral pain medications may be just as effective. This latter combination may be associated with greater motor block than sufentanil infusion (Table 5.5).
Non-Neuraxial Nerve Block
In this plane, it is possible to introduce local anesthetics posteriorly, in Petit's triangle, using the technique of loss of resistance and block the sensory innervation of the anterior abdominal wall. Patient-controlled analgesia (PCA) is effective and has become popular in some practices for cesarean analgesia. Intravenous (IV-PCA) and epidural (PCEA) PCA have been used for post-cesarean analgesia.
When meperidine is used for PCEA, women in labor consume approximately 50% less opioid via the PCEA route than via the IV-PCA route, and sedation scores are predictably higher in the IV-PCA group (Figure 5.11.
Nonsteroidal Agents (NSAIDs)
Clonidine and epinephrine (both of which presumably activate α-2 adrenergic receptors) and neostigmine (which prevents breakdown of synaptically released Ach) have also been used with PCEA. Furthermore, in many practices, cesarean sections are likely to be performed with a single-shot spinal anesthetic technique without inserting an epidural catheter. Ketorolac has also been administered IV on a scheduled basis after cesarean section with mixed results.
Its reported use as an oral analgesic in the post-cesarean section population has been very limited, but it has been used as a “rescue” analgesic in combination with other analgesic modalities, or as an alternative to an oral opioid if the parturient is intolerant.
Anesthesia for Reproductive Technologies
Hormonal therapies stimulate the production of multiple follicles in the ovaries per cycle, which subsequently allows multiple egg retrieval. Oocytes that have been successfully fertilized are usually transferred into the fallopian tubes or into the uterine cavity via a transcervical approach. Once mature, they are then injected directly into the distal fallopian tube with donor sperm via a laparosopic approach, after which in vivo fertilization takes place.
The optimal choice of anesthetics and techniques is unclear, but maintaining hemodynamic stability remains a primary concern regardless of anesthetic choice.
Anesthesia in Early Pregnancy
Other factors that are likely to be more important are the mother's illness and current illness, with fetal loss more likely after operations on the genitals (eg cervical suture), abdomen or pelvis. A joint statement on non-obstetric surgery in pregnancy by the American College of Obstetricians and Gynecologists and the American Society of Anesthesiologists notes: "No currently used anesthetic agents have been shown to have any teratogenic effects in humans when used at standard concentrations at any gestational age." .If the fetus is considered viable and the situation permits, expert advice should be sought, but at the same time, electronic fetal heart rate and contraction monitoring can be performed before and after the procedure to assess the well-being of the fetus and the absence of labor.
During assessment, be aware of the changes due to pregnancy and the exposure of the fetus to radiation during imaging.
