Pain Relief for Labor and Delivery

Updated: Dec 30, 2015
  • Author: Ralph W Yarnell, MD, FRCPC; Chief Editor: Carl V Smith, MD  more...
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Overview

Overview

Anesthetic care of the pregnant mother focuses on the safety and comfort of the parturient. It presents unique challenges along with the opportunity for gratifying physician-patient relationships. The use of epidural analgesia for labor has grown significantly over the past decades in the United States, and most women now request anesthesia services for the management of pain during labor. This article contains descriptions of numerous anesthetic and analgesic techniques to assist the birthing process, including intravenous analgesia, peripheral nerve blocks, neuraxial anesthesia, and general anesthesia.

The image below depicts pencil point spinal needles used in spinal anesthesia.

Earlier Quincke spinal needles had a biased cuttin Earlier Quincke spinal needles had a biased cutting edge that produce a cut opening in the dura. Newer "pencil-point" needles enter the dura with a fibre spreading action that significantly reduces the size of the dural rent, thereby reducing the incidence and severity of post dural – puncture headache. Drug is injected through a side hole at the distal end of the needle. Courtesy of Walter Zohmann, International Medical Development, Inc. (http://www.imd-inc.com/index.php).

See Pain Management: Concepts, Evaluation, and Therapeutic Options, a Critical Images slideshow, to help assess pain and establish efficacious treatment plans.

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Labor Pain Pathways

First stage of labor

The first stage of labor includes the latent and active phases. The latent phase begins with the onset of regular uterine contractions and ends when cervical dilation accelerates (after 4-5 cm of cervical dilation); the active phase begins at this point and ends when cervical dilation is complete. First-stage pain, therefore, relates to these regular uterine contractions and the subsequent stretching and dilation of the cervix.

Pain fibers from the uterus coalesce near the cervix in the right and left cervical plexi. Visceral afferent fibers travel from the paracervical region to join the hypogastric plexus, a loose collection of nerve fibers that transmit both afferent (visceral nociceptive) and efferent (sympathetic motor) impulses to structures within the pelvis. From the hypogastric plexus, pain transmission is carried toward the spinal cord in the lumbar paravertebral sympathetic chain. Nociceptive impulses enter the spinal cord via the dorsal nerve roots of T10 -–L1 before ascending toward higher centers via the spinothalamic tracts.

Second stage of labor

Near the end of the first stage of labor, the fetal head begins to descend, causing perineal distention and activating somatic nociceptive pathways. These somatic pain impulses are transmitted primarily via the pudendal nerves, which originate from the second through fourth sacral nerves. The somatic pain that arises during the second stage of labor occurs in addition to the ongoing visceral pain of uterine contractions.

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Psychophysical Approaches to Analgesia During Labor and Delivery

Patient education, a supportive environment, and training with nonpharmacologic analgesic techniques all appear to positively affect labor pain, particularly during the latent (early first stage) phase.

Three distinct psychophysical techniques have been developed as a means of facilitating the birth process and making it a positive emotional experience: "natural childbirth," psychoprophylaxis, and hypnosis.

Hypnosis for pain relief depends on the power of suggestion and has achieved periodic spurts of popularity since the early 1800s but has never gained wide appeal. Dick-Read developed the so-called natural childbirth method in the early 1930s and popularized in his book, Childbirth Without Fear. Dick-Read's approach emphasized the reduction of tension to induce relaxation. The psychoprophylactic technique was developed by Velvovski, who published the results of his work from Russia in 1950. Velvovski showed that obstetric psychoprophylaxis was a useful substitute for poorly administered labor anesthesia of the era. This concept of focused relaxation was later introduced in France by Lamaze and popularized in the United States by Bing and is now one of various relaxation techniques taught in childbirth classes

These techniques can significantly reduce anxiety, tension, and fear. They provide the parturient with a valuable understanding of the physiologic changes that occur during labor and delivery. In addition, they provide an opportunity for closer understanding and communication between the patient and her partner, who may be an important source of comfort.

Studies undertaken to assess the effectiveness of psychophysical techniques have reported widely divergent results. [1] There have been no randomized controlled trials, but uncontrolled reports have suggested these methods may be helpful for nulliparous patients, with effectiveness ranging from as low as 10%-20% to as high as 70%-80%. [2] These studies have not shown benefit for multiparous patients. Childbirth relaxation techniques have not been shown to reduce the incidence of epidural use during labor. The overall benefit is best judged by the parturient herself.

None of these psychophysical techniques should be forced on a patient, even by a skillful practitioner. The patient must not be made to feel that she has failed if she does not choose to complete her labor and delivery without analgesic medication. It must be made clear to the patient from the outset that she may ask for help if she feels she wants or needs it.

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Parenteral Pharmacologic Therapy

Systemic techniques of analgesia and anesthesia include both oral and parenteral routes of administration. Parenteral administration includes inhaled nitrous oxide, as well as subcutaneous, intramuscular, and intravenous injection. Sedatives, tranquilizers, and analgesics usually are given via intramuscular injection. In some cases, the intravenous route is preferred. The advantages of intravenous administration include the following:

  • Avoidance of variable rates of uptake due to poor vascular supply in fat or muscle
  • Prompt onset of effect
  • Titration of effect, avoiding the "peak effect" of an intramuscular bolus
  • Smaller effective doses because of earlier onset of action

The disadvantages of intravenous injection of opioids include maternal nausea, vomiting, sedation, and respiratory depression, as well as neonatal systemic effects, including respiratory depression. The goal is to administer the lowest concentration and the smallest dose necessary to obtain the desired effect.

Opioids form the mainstay of maternal systemic analgesia. Nearly all opioids, including morphine, meperidine, fentanyl, and remifentanil, have been used to provide analgesia during labor.

Morphine has limited application in contemporary obstetric practice owing to its higher rates of maternal and neonatal respiratory depression than meperidine or fentanyl.

Meperidine historically has probably been the most commonly used opioid in labor. Normeperidine, the principal metabolite of meperidine, has significant analgesic and respiratory depressant effects. Normeperidine levels peak in the fetus 1-3 hours after maternal intramuscular injection, leading some to advocate against intramuscular maternal administration if delivery is anticipated within 1-3 hours. However, studies examining the administration of meperidine during labor via an intravenous patient-controlled administration (PCA) device showed no association with reduced APGAR score, acidosis, or respiratory depression in neonates. [3]

Both fentanyl and remifentanil have short half-lives and are therefore often administered via PCA. Patients must be monitored closely, with appropriate nursing availability, continuous oxygen saturation monitoring, and immediate availability of anesthesia support.

Partial agonist and mixed agonist-antagonist opioids, such as butorphanol and nalbuphine, are sometimes used. These drugs have an inherent “ceiling effect” on both analgesia and respiratory depression. At low doses, they act primarily as agonists at the k-opioid receptor, providing analgesia and causing some depressant effects on respiration. At higher doses, they competitively antagonize the binding of other opioids at the µ-opioid receptor, reversing analgesia and respiratory depression. These agents provide modest analgesia and may infer some safety against the respiratory depressant effects of pure opioid agonists. However, respiratory depression can still occur in opioid-naïve patients with agonist–antagonist agents. In addition, these agents precipitate opioid withdrawal symptoms when they are given to patients who are regularly taking opioids.

Nitrous oxide is a potent analgesic in subanesthetic concentrations and has been used as inhaled analgesia during labor, primarily in commonwealth countries and where neuraxial anesthesia is not available. Its introduction to practice in the United States has been resisted, however, primarily because it is associated with significant room contamination of the gas, which would produce the risk of long-term exposure to labor room personnel. In addition, management of patients who become sedated from nitrous oxide exposure requires a unique skillset that is not otherwise part of the delivery room nurse’s experience. It is unlikely that the intrapartum use of nitrous oxide will become practice in American obstetric suites for these reasons.

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Peripheral Regional Analgesic Techniques Used in Obstetrics

The safety and suitability of peripheral regional anesthesia depend on proper selection of the drug and the patient and the obstetrician-gynecologist's knowledge, experience, and expertise in the diagnosis and treatment of possible complications.

Paracervical block

Clinical uses: This block is performed almost exclusively by an obstetrician to control first-stage labor pain, which is due to cervical dilation and stretching.

Anatomy: Visceral pain fibers from the uterus and cervix coalesce in the lateral fornix of the upper vaginal canal. This collection of nerves is termed the cervical plexus or Frankenhäuser ganglion.

Technique: A 14-cm 22-gauge needle is used, and care must be taken to limit needle penetration to the submucosa. The Iowa trumpet is a needle guide that can be used to limit the advance of the block needle beyond the “trumpet.” Local anesthetic is injected at the edge of the cervix at the 3 and 9 o’clock positions. Duration of analgesia varies from 45-90 minutes.

Complications: The proximity of the target nerves to the uterine artery means that paracervical injection may lead to high levels of local anesthetics in the fetus. Indeed, up to 70% of fetuses will have arrhythmias (principally bradycardia) within 10 minutes of injection. Fetal deaths from paracervical anesthesia have also been reported. [4] In addition, injections have occasionally been made directly into the fetal scalp. Because anesthesia lasts only 45-90 minutes, frequent reinjection may be necessary. Uterine artery hematoma, cervical abscess, and ureteral trauma have all been reported with this block. [5] This technique is uncommon in contemporary practice and is considered by some to be prohibitively dangerous because of the risk of fetal demise.

Pudendal nerve block

Clinical uses: Pudendal nerve blocks are useful in the second stage of labor to control the pain of perineal distention. This block technique is also useful for urgent forceps delivery (although the presence of the fetal head in the vagina can make needle placement challenging), as well as for providing analgesia for repair of episiotomy incisions or lacerations. The pudendal block is almost always placed by an obstetrician.

Anatomy: The pudendal nerves arise from the second through fourth sacral nerve roots and exit the pelvis via the greater sciatic foramen just superior to the ischial spine. They supply sensation to the distal portion of the vagina and the perineum. The pudendal artery and vein lie in close proximity to the nerve. The posterior femoral cutaneous nerve and the sciatic nerve lie somewhat posterior and lateral to the pudendal nerve at the level of the ischial spine.

Technique: A transvaginal approach is used when performing this block during labor. With the patient in the lithotomy position, the ischial spine is palpated through the vaginal wall, and a 22-gauge block needle is advanced posterior to it, with a slight posterior and lateral orientation of the needle. Advancing the needle 1-1.5 cm should place the needle tip through the sacrospinous ligament. The Iowa trumpet can also be used in this block to limit the advancement of the needle. The needle is aspirated to detect whether it is in a blood vessel. If there is no blood upon aspiration, a fast-acting local anesthetic (1% lidocaine or 2% chloroprocaine) is deposited. The procedure is then repeated on the patient’s other side to block the other pudendal nerve.

Complications: The pudendal artery and vein are in close proximity to the nerve; thus, intravascular injection can easily occur. . A pudendal block can result in high maternal blood levels of local anesthetic, retroperitoneal hematoma, and subgluteal abscess. [5]

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Neuraxial Techniques for Labor

Caudal analgesia

Caudal anesthesia is an epidural block performed by entering the caudal space via the sacral hiatus. This is the most inferior access point to the epidural space and is found at the junction of the coccyx and sacrum. It can provide selective sacral block for the second stage of labor; however, it is rarely used now because of complications specific to the obstetric patient. The descent of the fetal head against the perineum, in addition to the normal sacral edema of pregnancy, obscures the landmarks of the sacral hiatus. This makes the caudal procedure technically challenging, and reports of transfixing the rectum and fetal skull puncture with the epidural needle have led many anesthesiologists to avoid this technique. Lumbar epidural anesthesia is considered a safer approach to the epidural space.

Spinal analgesia

Spinal anesthesia is used for both cesarean surgery and specific situations during labor. Medication is deposited into the cerebrospinal fluid (CSF)–filled intrathecal space as a single shot using pencil point spinal needles of very small dimension (see image below).

Earlier Quincke spinal needles had a biased cuttin Earlier Quincke spinal needles had a biased cutting edge that produce a cut opening in the dura. Newer "pencil-point" needles enter the dura with a fibre spreading action that significantly reduces the size of the dural rent, thereby reducing the incidence and severity of post dural – puncture headache. Drug is injected through a side hole at the distal end of the needle. Courtesy of Walter Zohmann, International Medical Development, Inc. (http://www.imd-inc.com/index.php).

Advantages of spinal analgesia include rapid onset of analgesia, the potential for minimal motor block, little or no risk of systemic local anesthetic toxicity, minimal drug transfer to the fetus, and modest anesthesiologist staffing requirements. The dose and concentration of the local anesthetic can be tailored to the situation, with small doses of local anesthetic and opiate mixtures providing 1-3 hours of labor analgesia and larger doses producing surgical blocks suitable for cesarean section or other surgery.

The major limitation of spinal analgesia during labor is its limited duration, since it is typically a single-injection technique. If labor outlasts the duration of the spinal analgesic, it must be repeated or followed with systemic anesthesia. Efforts to overcome this fundamental limitation involve using either larger doses of the spinal drugs or agents with longer duration. Both approaches carry risks: larger doses may lead to more side effects, and the use of drugs with longer duration may result in effects that far outlast labor and delivery.

The most common agents used for spinal analgesia during labor are long-acting local anesthetics, lipophilic opioids, and adjuvant drugs such as epinephrine. Drugs are almost always used in combination to gain rapid onset, sufficient duration, and additive or synergistic analgesic effects. Synergy between spinally administered local anesthetic and opioid is most potent for the visceral pain of the first stage of labor and less so for the somatic pain of the second stage. Clinically, this translates into excellent to good analgesia during the first stage of labor, and fair to poor analgesia during the second stage.

Bupivacaine, a long-acting local anesthetic, is the most common local anesthetic used for spinal labor analgesia. Low doses are used to minimize motor block and maternal hypotension. Opioids are also frequently used, usually in combination with bupivacaine. Fentanyl or sufentanil provides a rapid analgesic effect with approximately 90-minute duration. Higher doses of sufentanil were once routinely used but were associated with a higher incidence of fetal bradycardia and occasional maternal respiratory depression. When delivery is not expected for more than 2 hours, morphine may be used.

Intrathecal morphine has been associated with delayed maternal respiratory depression up to 18 hours after injection and with recurrence of oral herpes lesions. Urinary retention, pruritus, and nausea/vomiting are all significantly more common with this drug than with fentanyl or sufentanil. Some practitioners administer continuous infusions of low-dose naloxone or oral naltrexone after delivery to diminish the side effect profile of intrathecal morphine.

The inclusion of epinephrine increases analgesic duration by as much as 45 minutes with some drug combinations. However, the incidence of nausea and motor block are also increased. Although a number of dosing combinations of local anesthetic and narcotic are used for spinal labor analgesia, the most common mixture is 1 mL of 0.25% bupivacaine with 25 µg of fentanyl as a single-shot intrathecal dose. A surgical block for cesarean surgery requires 1.4-1.6 mL of 0.75% bupivacaine with fentanyl or sufentanil added.

Complications

Numerous complications can arise from spinal anesthesia. The most common is the postdural puncture headache (PDPH), also known as a “spinal headache,” which develop from minutes to days after a dural puncture. Its hallmark is its positional nature: it is markedly worse while sitting up or standing than while supine. Spinal headaches occur in 1%-2% of spinal punctures with a 25-gauge Whitaker spinal needle. This is a dramatic improvement from the 25% incidence seen with the 22-gauge Quincke needle, [6] which had impeded spinal use in pregnancy prior to 1990.

Therapy for PDPH includes recumbent position, hydration, oral analgesia, and, in severe cases, epidural injection of 10-20 mL of the patient's fresh blood to "seal" the defect (known as a “blood patch”). The need for a blood patch is influenced by patient age, patient sex, and the size and type of needle. Women of childbearing age have a greater likelihood of developing PDPH; however, the design of pencil-point needles has reduced the incidence of headache to 1%-2%. As importantly, PLPH caused by these needles resolves quickly and rarely requires blood patch therapy.

After placement of the spinal block, the anesthesiologist must monitor the patient for evidence of dermatomal spread of anesthesia. A block below T10 is insufficient to control uterine pain, and a high thoracic level may produce hypotension that will require treatment.

Spinal anesthesia produces hypotension in 10%-20% of cases, which presents risks to both mother and fetus. This is a result of arterial and venous vasodilation within the dermatomes that receive a sensory block. If high thoracic dermatomes (T1-T5) are anesthetized by the spinal injection, alteration of the cardiac sympathetic innervation slows the heart rate and reduces cardiac contractility. Epinephrine secretion by the adrenal medulla is also depressed. Concomitantly, the unopposed parasympathetic effect of cardiac slowing alters vagal stimulations.

As a result of these and related changes, shock follows promptly, particularly in hypotensive or hypovolemic patients. This is why essential elements of obstetric anesthesia include adequate intravenous hydration prior to administration of spinal anesthesia and frequent monitoring of maternal blood pressure after anesthesia is given. Any decrease in maternal blood pressure is rapidly corrected with intravenous fluids or a vasopressor.

Rarely, significant complications can develop following a dural puncture. Infection in the form of an epidural abscess or bleeding in the form of an epidural hematoma can lead to pressure on the spinal cord (cauda-equina syndrome) and cause nerve damage that may become permanent.

Epidural analgesia

Epidural techniques are common and effective methods of providing analgesia during labor and anesthesia for cesarean delivery.

An epidural involves placement of an indwelling catheter into the epidural space. The epidural catheter can then be used to deliver a continuous epidural infusion (CEI) of analgesic medication via a programmable pump. This technique allows rapid initiation of analgesia, minimal motor block, flexibility for varying clinical situations that evolve, and longer duration of effect than spinal anesthesia since an epidural catheter can be left in place for hours and possibly days, if necessary.

Often, the infusion system can incorporate patient autonomy. Patient-controlled epidural analgesia (PCEA) still involves a programmable pump to infuse the medication at a constant basal rate. Additionally, the parturient is given a button attached to the pump and instructed to press it if she becomes uncomfortable. This triggers the pump to give an additional bolus dose. Patients typically consume less total drug with PCEA compared to CEI, require fewer anesthetic personnel interventions, have no increased side effects, and have very high satisfaction. Compared with intravenous analgesia, patients with PCEA have lower pain scores, higher satisfaction levels, and less need for neonatal resuscitation.

While the second stage of labor is prolonged by epidural anesthesia, the duration of the first stage is unaffected. The use of outlet forceps is increased, but cesarean section rates are unchanged.

Epidural analgesia and anesthesia using local anesthetics have been in widespread use for decades. Historically, practitioners tended to use high concentrations of local anesthetic alone, which afforded excellent pain relief but often came at the expense of significant motor blockade and hypotension. Today, it is recognized that initiating analgesia with minimal motor block can be accomplished with low-concentration, high-volume epidural solutions. The analgesic synergy of a local anesthetic in combination with an opioid allows for very dilute concentrations of local anesthetic.

Complications

The most common risks associated with epidural analgesia during labor result from the consequences of sympathetic blockade or the unrecognized misplacement of the epidural catheter into an epidural vein or the intrathecal space. Hypotension after initiation of epidural or combined spinal-epidural analgesia (CSE) techniques occurs in approximately 10% of cases and typically is most pronounced at 15-20 minutes after initiation of neural blockade. Uterine blood flow is directly proportional to uterine arterial pressure, so maternal hypotension can lead to inadequate fetal-placental perfusion.

After initiation of labor analgesia, patients can be placed in a full or partial lateral position to prevent aortocaval compression by the gravid uterus, which may dramatically impede venous return and contribute to hypotension. Hypovolemia can be corrected by using intravenous hydration prior to placing the block. An intravenous bolus of crystalloid solution modestly reduces the incidence of significant hypotension following initiation of either spinal or epidural analgesia. If the maternal blood pressure falls in excess of 20% of the preblock level or any new fetal heart rate abnormalities appear, small doses of an intravenous vasopressor can be used to correct the hypotension.

Placement of the epidural catheter into an epidural vein occurs in approximately 5% of obstetric patients. This is much higher than in the nonobstetric population owing to epidural vein engorgement caused by compression of the vena cava by the gravid uterus. If intravenous catheter placement goes unrecognized, systemic local anesthetic toxicity (manifested by events as severe as seizures or cardiac toxicity) may result, although this is rare. Intravenous placement typically occurs with initial epidural catheter placement but may develop hours later, likely due to catheter movement as the patient changes position. If venous cannulation occurs, blood often spontaneously appears in the epidural catheter. Gentle aspiration of the catheter may also reveal blood. It is important to keep in mind that an epidural catheter may be intravenous even when no blood is seen during aspiration through the catheter.

Epidural catheters can also be unknowingly placed in the intrathecal (or spinal) space. The local anesthetic dose required for typical spinal anesthesia is approximately 15% of the dose required for epidural anesthesia; therefore, if a typical epidural dose is unintentionally administered spinally, a rapid spinal block involving the phrenic nerve, all sympathetic nerve fibers, and the brainstem will occur. This is clinically termed total spinal anesthesia. Prevention of total spinal anesthesia is similar to the previous discussion of intravascular epidural catheters. Spontaneous flow of CSF can sometimes be observed from either the epidural needle or catheter. Epidural catheters can also be aspirated prior to administering medication, with the appearance of clear to blood-tinged fluid suggesting intrathecal placement.

Many clinicians use an initial test dose to identify intrathecal or intravenous placement. This test dose contains an amount of local anesthetic, which would provide a recognizable and safe spinal anesthetic if injected intrathecally, as well as epinephrine, which would signal intravenous placement through increased heart rate and blood pressure. Owing to the large differences in dose requirements, this dose of local anesthetic should be insufficient to cause a significant epidural block. A rapid rise in maternal heart rate suggests an intravascular catheter, while a significant sensory block developing 2-5 minutes after the test dose administration suggests an intrathecal catheter.

Epidural blocks that seem unusually high or “dense” also suggest unintentional spinal placement. As maternal heart rate also increases during active contractions, some clinicians recommend timing the test dose injection with the end of the previous contraction.

Even with this approach, interpretation of epinephrine test doses in the parturient can be challenging. Clinicians may choose to fractionate local anesthetic boluses given via the epidural catheter, dividing the intended dose into 3-4 smaller doses administered over 5-10 minutes in hopes of detecting improper catheter placement. Any previously functioning epidural catheter that suddenly becomes ineffective should be suspected of having migrated into an epidural vein.

As mentioned in Spinal anesthesia, accidental puncture of the dura with an epidural needle or intentional puncture of the dura during CSE can lead to a spinal headache. Epidural abscess, hematoma, and nerve damage are also rare but possible complications.

Combined spinal-epidural analgesia

It is possible to combine the advantages of spinal analgesia (fast onset of analgesia, profound potency of opioids delivered intrathecally) with the duration and flexibility of an epidural catheter. This is known as combined spinal-epidural analgesia (CSE). The technique adds the placement of intrathecal local anesthetic and opiate at the same time as the placement of the epidural catheter.

Most commonly, after the epidural needle has been advanced into the epidural space, as illustrated above, a spinal needle is advanced through the epidural needle into the intrathecal space, and a small amount of medication is injected. The spinal needle is removed, and an epidural catheter can then be threaded via the epidural needle, which still remains in the epidural space. Once the catheter is in place, the epidural needle is removed. The intrathecal medication provides immediate sacral analgesia, which is appropriate for parturients entering the second stage of labor. The epidural catheter can be used to as part of a PCEA, as described in Epidural analgesia.

Additional benefits of this option include decreased total neuraxial drug consumption due to minimal need for epidural medications in the first 2 hours after the spinal injection, an increased effectiveness of epidural medications after use of the CSE technique (presumably from facilitated epidural drug entry into the CSF via the dural opening produced during spinal placement), and a decreased unintentional dural puncture (“wet-tap”) rate with the epidural needle.

Several other favorable outcomes have been noted in relation to CSE. CSE labor analgesia is associated with faster cervical dilation than conventional epidural labor analgesia, perhaps owing to the minimal local anesthetic motor block that accompanies most CSEs. CSE techniques have a lower rate of epidural catheter replacement during labor than conventional epidural catheter placement. This outcome is probably consequent to confirmation of epidural needle location by obtaining CSF via the long spinal needle. Finally, failure of an epidural to provide adequate anesthesia for cesarean delivery is more likely after conventional epidural catheter placement than CSE.

Some disadvantages of CSE labor analgesia are apparent. It impairs the ability to evaluate the subsequent epidural dosing for unintended intrathecal spread. One of the major reasons to give an epidural test dose is to identify intrathecal placement of the epidural catheter. This test dose is usually accomplished by a small local anesthetic dose via the catheter and observing the patient for rapid development of spinal anesthesia.

Critics of CSE believe that, because the initial CSE dose is usually administered prior to placing the epidural catheter and results in rapid spinal analgesia, it is difficult to exclude the possibility of unintentional intrathecal placement of the epidural catheter. No clinical studies have been conducted to confirm or refute this critique. Another criticism of CSE analgesia is that ineffective epidural catheters are not discovered until the initial intrathecal block has dissipated, which is approximately 90 minutes after initiation of CSE labor analgesia. This is a clinical trade-off; there are fewer epidural block failures with CSE, but those that do occur are not immediately apparent.

Because of these drawbacks to the CSE technique, CSE has become the default procedure for labor analgesia in only 8% of US obstetric units. It is now largely reserved for situations in which a multiparous patient is near full dilation at the time of block placement. In this situation, the intrathecal drug produces sacral blockade and relieves the perineal pain caused by fetal head descent. These sacral dermatomes are not anesthetized in the early phase of epidural anesthesia.

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Contraindications to Neuraxial Anesthesia During Labor and Delivery

Patient refusal

A patient may decline neuraxial anesthesia if she would prefer an unmedicated labor and delivery. Such refusal is a contraindication to providing the block. The patient should be given an opportunity to discuss options for pain relief if her caregivers feel she has questions and concerns that can be clarified. The patient should be well-informed, and her wishes are paramount in considering managing the pain of labor.

Coagulopathy

The presence of a significant coagulopathy merits concern owing to the risk of creating an epidural hematoma during administration of a neuraxial anesthetic and the possibility of subsequent neurologic injury as the blood clot expands and compresses nerves in the spinal canal. A patient may have a medication-induced coagulopathy due to treatment of an existing medical condition or administration of an antithrombotic agent. Readers may refer to the American Society of Regional Anesthesia guidelines for further information on these medications.

She may also have a disease process that impairs clotting. The most common coagulation disturbance of pregnancy is thrombocytopenia, occurring in 1%-2% of parturients, [7] and its most common etiology is preeclampsia, particularly in the subset of patients who develop HELLP syndrome. The decision to place or not place a spinal or epidural in the setting of known or suspected coagulopathy is at the discretion of the anesthesia provider and the parturient and not dependent solely on a specific platelet count. Some anesthesiologists may refuse to provide regional anesthesia if the platelet count is lower than 100,000 x109/L.

When confronted with a woman with thrombocytopenia, other anesthesiologists instead perform a coagulation-directed history and physical examination, including such items as recent onset of easy bruising, bleeding gums with tooth brushing, bleeding from venipuncture sites, and inspection of the nail beds, palate, and sclera for petechiae.

Examination of the airway is also important. When considering the risks of regional anesthesia, the anesthesiologist must also consider the risks of general anesthesia if regional anesthesia is not provided. Pregnant patients are more likely to have significant airway edema than their nongravid counterparts, increasing the risk for difficult intubation.

Infection

The use of neuraxial regional anesthesia in the presence of systemic sepsis or cellulitis at the lumbar puncture site is ill advised because those circumstances pose an unknown risk of seeding the neuraxis with microorganisms. The hemodynamic instability associated with septic shock combined with the sympathetic blockade of regional anesthesia could also prove catastrophic.

Much more common than systemic sepsis or localized cellulitis during labor is chorioamnionitis, a polymicrobial infection of the amniotic fluid and placental components often seen during prolonged rupture of the membranes. The diagnosis is made clinically, usually based on the combination of maternal fever and a tender uterus. Chorioamnionitis that is not associated with systemic sepsis does not contraindicate epidural or spinal anesthesia. In a retrospective study of 517 parturients who had received epidural anesthesia and 14 who had received spinal anesthesia before delivery and whose placentas were subsequently found to be positive for chorioamnionitis, no evidence of neuraxial abscess nor meningitis was found. [8]

Bleeding and hypovolemia

Uncorrected hypovolemia is another contraindication to regional anesthesia. During parturition, hemorrhage is the most common cause of significant hypovolemia. Maternal hemorrhage is a leading cause of maternal mortality, most commonly due to placenta previa or abruptio placenta. Placental abruption is accompanied by disseminated intravascular coagulopathy (DIC) in 10% of cases, which poses further risk with neuraxial anesthesia. During vaginal birth after previous cesarean delivery (VBAC), uterine rupture can also lead to life-threatening hemorrhage. In the postpartum period, uterine atony and uterine inversion may be associated with significant bleeding, which may contraindicate regional anesthesia. In all cases, maternal volume resuscitation and coagulation correction must precede consideration of regional anesthesia.

Fetal distress

Severe fetal distress may suggest the need for general anesthesia for emergent cesarean delivery. Most commonly, prolonged fetal bradycardia leads to this request. Anesthesiologists must remember that their primary concern is the mother’s health. Therefore, when the airway examination strongly suggests that endotracheal intubation will be difficult, a regional anesthetic may still be appropriate. Not all nonreassuring fetal heart rate tracings are an indication for absolute haste.

The obstetrician and anesthesiologist must communicate clearly and specifically their concerns and plans in each individual case so that the most appropriate decisions can be made for combined management. If particular maternal risks are identified earlier in labor (eg, extreme obesity or a difficult airway), these risks should be discussed with the team in order to hopefully preempt the need for urgent care.

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Regional Anesthesia for Elective Cesarean Delivery

There are many benefits to using regional anesthesia for elective cesarean sections. Outcome studies suggest that regional anesthesia is safer for the mother, although both regional and general anesthetics are safe. [9] Outcome comparisons are difficult because general anesthesia is now reserved for urgent, unstable, and complex cases. Maternal awareness during the birth and more immediate mother-newborn bonding are well appreciated. Regional anesthesia also facilitates postoperative pain control. The addition of short-acting lipophilic opioids to epidural or spinal anesthesia provides 2-6 hours of postoperative analgesia. Alternatively, adding morphine provides 10-15 hours of analgesia. Maternal morbidity is better with regional anesthesia for cesarean birth, with mothers ambulating and breastfeeding sooner. Well-conducted general and regional anesthesia results in good neonatal outcomes as measured by APGAR scoring and umbilical acid-base status.

The choice between epidural and spinal anesthesia for cesarean delivery has been greatly simplified by the development of pencil-point spinal needles. These needles are associated with postdural puncture headache rates of less than 1%, a large improvement over the cutting-tip spinal needles. For elective cesarean delivery, spinal anesthesia is often appropriate. Compared with epidural anesthesia, spinal anesthesia has a higher success rate, is easier to perform, has a more rapid onset, has minimal potential for systemic toxicity, and typically results in more intraoperative comfort.

Epidural anesthesia may be preferable in a few patients presenting for elective cesarean delivery. Patients with significant systemic disease, particularly diabetes, preeclampsia, and chronic hypertension, may benefit from the slower onset and more controlled hemodynamics of epidural analgesia. Furthermore, epidural anesthesia has been shown to reduce the catecholamine levels associated with pregnancy-induced hypertension. Motor block is typically less profound with epidural anesthesia, which may benefit patients with severe pulmonary disease. When a lengthy surgical duration is anticipated, epidural anesthesia may be preferable, as re-dosing can provide anesthesia of unlimited duration. Also, in patients with a high likelihood of difficult-to-manage pain, postoperative epidural infusion can provide postoperative analgesia.

If an epidural is in place and functioning well for labor analgesia when a decision to section is made, the epidural catheter may be used for conversion to a surgical block by using higher-concentration anesthetic solution titrated to a T4-T6 level. If the effectiveness of the labor epidural is questioned, the anesthesiologist will likely choose to remove the catheter and proceed with spinal anesthesia for the surgery.

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General Anesthesia

General anesthesia is indicated for cesarean section delivery when regional techniques cannot be used because of coagulopathy, infection, and/or hypovolemia or if surgery needs to take place faster than the anesthesia provider believes a neuraxial technique can be placed. While overall maternal mortality relating to anesthesia has been reduced 10-fold since the 1950s, general anesthesia continues to pose a larger risk to parturients than regional anesthesia.

The case fatality rate for cesarean delivery is 6.5 deaths per million when performed under general anesthesia compared to 3.8 deaths per million when regional anesthesia is administered. [9] The primary reason for this difference is the fact that general anesthesia is now reserved for urgent, complex cases. Overall, anesthetic mortality is low for both groups.

Ideally, general anesthesia for cesarean section delivery should cause the mother to be unconscious, feel no pain, have no unpleasant memories or awareness of the procedure, and provide good operating conditions for the surgeon. The fetus should not be jeopardized, with minimal cardiorespiratory depression and intact reflex irritability.

General anesthesia for cesarean section delivery is modified from the typical nonobstetric technique. A rapid sequence technique with cricoid pressure is used, with recognition that the risks for the term obstetric patient include the following:

  • Full stomach and potential aspiration
  • Difficulty with laryngoscopy and intubation due to the edema of the airway that occurs with pregnancy
  • Increased sensitivity to sedative medication
  • Rapid desaturation if intubation is unsuccessful

Airway edema is even more pronounced if the patient has been actively laboring.

Preoperative medication usually is not required when the patient is brought to the cesarean section room. The patient should be prepared with 30 mL of a nonparticulate oral antacid to offset gastric acidity. The patient is given 100% oxygen with a close-fitting mask for 3 minutes prior to induction.

When the surgeon is ready to make the incision, an induction agent is given intravenously and cricoid pressure applied by an assistant. Immediately, a neuromuscular blocking agent should be administered and intubation and inflation of the cuff performed. Intubation is confirmed by auscultation and monitoring end-tidal CO2 before the cricoid pressure is released and the incision made. After 6-8 breaths of 100% oxygen, the patient should be given nitrous oxide 50% with oxygen 50% until delivery of the fetus.

Low concentrations of sevoflurane or isoflurane (0.5 MAC) will reduce the incidence of awareness. An attempt must be made to keep the induction-to-delivery time under 10 minutes, as good neonatal outcomes are anticipated if induction-to-delivery times and uterine incision-to-delivery times are kept to a minimum.

After delivery of the fetus, the nitrous oxide concentration can be increased to 70% if oxygen saturation is more than 98%. Intermediate-acting muscle relaxants can be used to maintain paralysis, and intravenous narcotics and benzodiazepines may be injected for supplemental anesthesia. An orogastric or nasogastric tube is placed to empty the stomach. Once the surgery is complete, the patient should be positioned on her side and fully awakened before extubation.

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Anesthesia and Analgesia for Miscellaneous Obstetric Procedures

Cervical cerclage

A nonfunctioning (“incompetent”) cervix is a leading cause of early second-trimester miscarriage. Therapy is usually placement of a purse-string suture (cerclage) in the cervix at about 12 weeks' gestation followed by removal at approximately 37 weeks' gestation. Both placement and removal of cervical cerclage are typically performed with low-dose spinal anesthesia using bupivacaine or chloroprocaine. Lidocaine is used less frequently because of the risk of transient neurologic syndrome, which can result in buttock pain for a few days postoperatively.

External cephalic version

This procedure typically involves gentle transabdominal pressure simultaneously applied to head and buttocks of a fetus that is near or at term and known to be in the breech position. The obstetrician attempts to “roll” externally the fetus into a position more amenable to vaginal delivery. External versions are usually performed at approximately 36 weeks’ gestation. At earlier gestational ages, the fetus will often return to the original lie sometime after the version. With attempts at version much beyond 36 weeks, success rates are low.

Again, low doses of short-acting spinal anesthetics may be used; however, there is concern that analgesia may facilitate excessive force to be used in the version attempts and contribute to fetal or placental injury. If immediate cesarean delivery is required following version attempts, the low-dose spinal would be insufficient for surgical anesthesia, so a full surgical spinal anesthetic block or general anesthesia will need to be performed.

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Postpartum Tubal Ligation

Postpartum tubal ligation is easily accomplished in the days following delivery, before the uterus recedes into the pelvis. Regional anesthesia is optimal because the same physiologic changes of pregnancy that make general anesthesia risky for cesarean delivery continue into the postpartum period.

Spinal anesthesia is now the anesthetic of choice for postpartum tubal ligation. The will provide a quick, reliable surgical block, and smaller doses of local anesthesia are required than for cesarean section because the surgery is of shorter duration. If epidural anesthesia has been used for labor analgesia, it is often difficult to produce adequate surgical anesthesia if the interval from delivery to surgery is more than 6 hours. It is common practice to simply remove the labor epidural catheter and proceed directly with spinal anesthesia for the procedure.

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Summary

Obstetric analgesia and anesthesia is a uniquely challenging and rewarding field. The anesthesiologist must consider numerous facets of physiology, pharmacology, drug transfer, and coexisting disease, all within an emotionally charged environment. Despite these multiple challenges, one can dramatically improve patient safety and comfort with expertise in regional anesthesia.

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