Labor and Delivery, Analgesia, Regional and Local

Laboring patients must be educated about the different available methods of labor analgesia. Many pharmacological and nonpharmacological methods of labor analgesia have been adopted over the years. Of these, neuroaxial or regional analgesia has become the most popular method. Possible regional anesthesia techniques include epidural analgesia, spinal analgesia (sometimes referred to as the intrathecal or subarachnoid space), or a combination of epidural and spinal analgesia. Approximately 60% of laboring women (2.4 million each year) choose regional analgesia for pain relief during labor. ^{[1, 2]}

Uterine contractions and cervical dilatation result in visceral pain. These pain impulses are transmitted by afferent, slow conducting, A-delta and C fibers that accompany the sympathetic nerves and enter the spinal cord at the T10 to L1 level. As labor progresses, the descent of fetal head and subsequent pressure on the pelvic floor, vagina, and perineum, generates somatic pain, which is transmitted by the pudendal nerve (S2-4). These rapidly conducting somatic pain fibers are relatively difficult to block.

In obstetric patients, regional analgesia refers to partial or complete loss of pain sensation below the T8 to T10 spinal level. In addition, a varying degree of motor block may be present, depending on the agents used. Advantages of regional analgesia include the following:

• Provides superior pain relief in first and second stages of labor

• Facilitates patient cooperation during labor and delivery

• Provides anesthesia for episiotomy and instrumental delivery

• Allows extension of anesthesia for cesarean delivery

• Avoids opioid-induced maternal and neonatal respiratory depression from intravenous opioids

Besides providing analgesia in labor, regional analgesia may facilitate atraumatic vaginal delivery of twins, preterm neonates, and neonates with breech presentation. It also helps control blood pressure in women with preeclampsia by alleviating labor pain, and it blunts the hemodynamic effects of uterine contractions and the associated pain response in patients with other medical complications.

Maternal request is a sufficient medical indication for pain relief during labor. ^[3]

Analgesia is indicated for patients with certain risk factors even in the absence of maternal request. This is to help minimize the need for emergency anesthesia in patients for whom such anesthesia would be especially hazardous. Patients with any of the following risk factors should be referred early to the anesthesia service for prompt consultation to permit a joint management plan:

• Marked obesity

• Obstetric complications with potential for operative delivery (eg, placenta previa, high order multiple gestation)

• Severe preeclampsia

• Bleeding disorders (eg, thrombocytopenia)

• Use of anticoagulants

• Severe edema, trauma, surgery, or anatomical abnormalities of the face, neck, or spine

• Abnormal dentition, small mandible, or difficulty opening mouth

• Extremely short stature, short neck, or arthritis of the neck

• Goiter

• Prior history of anesthesia complications, such as malignant hyperthermia

• Cardiovascular, neurological, or respiratory disease

• Hyperreflexia in parturients with a high spinal cord lesion (prevention or treatment)

Regional anesthesia is contraindicated in the presence of actual or anticipated serious maternal hemorrhage, refractory maternal hypotension, coagulopathy, untreated bacteremia, raised intracranial pressure, skin or soft tissue infection at the site of the epidural or spinal placement, and anticoagulant therapy. ^[4]

Regional analgesia is also contraindicated in cases of patient refusal or inadequate practitioner training and experience.

As exacerbation of neurological diseases might be attributed without cause to the anesthetic agent, many clinicians avoid regional anesthesia in its presence.

Other maternal conditions such as aortic stenosis, pulmonary hypertension, or right-to-left shunts are also relative contraindications to the use of regional analgesia. Only opioids could be used for labor analgesia in these situations, as they do not decrease systemic vascular resistance. For patients with mitral stenosis, regional analgesia (epidural) is the preferred method.

In women with severe preeclampsia, analgesia is controversial.

• Obstetrical concerns from regional analgesia include hypotension induced by sympathetic blockade, danger from pressor agents given to correct hypotension, and potential for pulmonary edema following infusion of large volumes of crystalloid.

• Conversely, general anesthesia with tracheal intubation may result in severe sudden hypertension, further complicated by cerebral or pulmonary edema or intracranial hemorrhage.

• Over the past 2-3 decades, most obstetric anesthesiologists have come to favor epidural blockade for labor analgesia in women with severe preeclampsia. ^[5]

Many anesthesiologists do not use regional analgesia in the presence of thrombocytopenia, though the precise platelet count needed for safety is unknown.

• Currently, practitioners routinely perform regional analgesia with platelet counts below 100,000, although few will instrument the spinal/epidural space if the platelet count is below 50,000. Several studies have reported no complications in women with platelet counts between 50,000-100,000 who received epidural analgesia. ^{[6, 7, 8]}

• The rate of decline of platelet count is more important than the absolute number. Besides the count, the adequacy of platelet function must also be considered, particularly in patients with pregnancy-induced hypertension or the HELLP (hemolysis, elevated liver enzymes, and low platelets) syndrome.

Special precautions are needed for patients taking anticoagulants to avoid epidural or spinal hematoma. ^[9] See ACOG Recommendations for more information. ^[10]

Regional anesthesia could be safely administered to patients taking aspirin or unfractionated heparin prophylaxis. However, patients taking therapeutic doses of unfractionated heparin should discontinue the medication the night before a planned induction or cesarean delivery, or with the spontaneous onset of labor. The clinician should ensure that the activated partial thromboplastin time (aPTT) is within the reference range.

• Similarly, the patient’s coagulation status should be evaluated before the epidural catheter is removed. Heparin should never be initiated within 1-2 hours of insertion or removal of the epidural catheter. Because patients taking therapeutic heparin for more than 4 days could have thrombocytopenia, platelet count should be assessed in these patients prior to regional block or epidural catheter removal.

• Unlike with unfractionated heparin, patients taking low molecular weight heparin (LMWH) need to wait for 12 hours following the last prophylactic dose and at least 24 hours following the last therapeutic dose prior to receiving a regional block. Once placed, the epidural catheter should not be removed for at least 10-12 hours from the last dose of LMWH. Preferably, heparin should be initiated after removal of the epidural catheter. For rare patients who need LMWH prophylaxis in the presence of epidural catheter, low-dose epidural technique should be used to permit careful monitoring of neurological function.

• Following surgery, wait 24 hours to commence twice-daily LMWH (ie, enoxaparin) and wait 6-8 hours to commence once-daily LMWH. If blood is seen during administration of regional anesthesia, LMWH should not be administered for 24 h postoperatively, irrespective of the dose frequency.

Nonreassuring fetal heart tone is not a contraindication to regional analgesia. However, some physicians may be reluctant to recommend epidural anesthesia in this situation. The prior placement of a functioning epidural catheter may allow rapid extension of the block, should cesarean delivery be required for fetal distress.

Various classes of analgesics used for epidural and spinal analgesia include local anesthetics, opioids, and adrenergic agonists. Local anesthetics alone can provide adequate analgesia throughout labor. However, the concentration of local anesthetic needed to maintain analgesia often results in motor block. The administration of an opioid alone provides moderate analgesia during early labor, but the dosage needed to maintain analgesia results in significant adverse effects. Further, an opioid administered alone provides inadequate analgesia during the advanced phase of the first stage of labor, the second stage of labor, or operative delivery. When an opioid is used in combination with a local anesthetic, it provides faster onset of effective analgesia throughout labor with minimal adverse effects. Physician preference often dictates the route and the medication or combination of medications used to provide labor analgesia.

Local anesthetics

See the list below:

• Bupivacaine is used most often for spinal (subarachnoid [intrathecal]) analgesia.

  • Bupivacaine has a favorable sensory-motor differential block at low concentrations. This results in analgesia with motor sparing, thus enabling ambulation, which has made bupivacaine a popular choice for labor analgesia.

  • Relatively high concentrations of bupivacaine (0.25-0.75%) were formerly administered in the epidural space for labor and cesarean delivery. For laboring patients, these doses resulted in frequent motor block and, more ominously, the 0.75% concentration was implicated in multiple cases of cardiac arrest in parturients. ^[11]

  • Bupivacaine cardiotoxicity is particularly difficult to reverse and, unlike with other anesthetics, this cardiotoxicity could be seen without preceding neurotoxicity. ^[11] As a result, the US Food and Drug Administration (FDA) recommends that bupivacaine in concentrations >0.5% not be used in obstetric patients.

  • Current labor analgesia regimens employ much lower concentrations of bupivacaine, usually ≤0.25%, and often ≤0.125%. The use of these low concentrations reduces the likelihood of systemic toxicity and hypotension, but this low-strength bupivacaine has a relatively slow onset of analgesic action. On average, this low concentration of bupivacaine, when combined with opioids, begins to provide epidural analgesia 5-10 minutes after injection; and maximal effect may not be achieved for 15-20 minutes.

• Ropivacaine is a bupivacaine isomer and is used most often for epidural analgesia.

  • Like bupivacaine, the favorable sensory-motor differential block at low concentrations of ropivacaine has made it a popular choice for labor analgesia.

  • Ropivacaine causes less motor block and cardiotoxicity than bupivacaine. ^[12] If cardiotoxicity occurs with ropivacaine, it is more amenable to treatment. However, ropivacaine is 60% as potent as bupivacaine when administered by the epidural route in laboring patients. ^{[13, 14]} This difference in potency might explain the perceived benefits of ropivacaine with regard to systemic toxicity and sensory-motor differential.

• Lidocaine is used less often today as the primary agent to provide labor analgesia.

  • The disadvantages of lidocaine include 1) less differential block, 2) shorter duration of action, and 3) higher association with transient neurological symptoms. ^[15] The transient neurological symptoms manifest as either transient pain or dysesthesia in the legs or buttocks that persists for a few days after the intrathecal lidocaine administration. A more ominous concern is the association of cauda equina syndrome with intrathecal lidocaine.

  • Because of concern about neurological symptoms, many practitioners have abandoned the use of regional lidocaine in favor of arguably safer alternatives, except for cases that require rapid extension of epidural for vaginal or cesarean delivery. The faster onset of action of lidocaine helps in this situation.

Opioids

See the list below:

• Of the opioids used most often for regional analgesia, fentanyl and sufentanil are more lipid-soluble. This solubility results in a faster onset of analgesia, a short duration of action, and minimal adverse effects.

• Morphine is also used for regional analgesia. However, it has poor lipid solubility, slow onset of action, prolonged duration of analgesia, and higher incidence of adverse effects.

• Regional block with opioids (except meperidine) achieves analgesia but not surgical anesthesia. This effect potentially benefits patients who want pain relief but also a fuller participation in the delivery experience. If surgical manipulation becomes necessary during labor and delivery, local anesthetics would have to be administered via the epidural or spinal route to provide further analgesia or anesthesia.

Epinephrine

See the list below:

• Epinephrine, an adrenergic agonist, is sometimes added at a concentration of 1:200,000 to 1:800,000 to the solution of local anesthetics for epidural analgesia but not for intrathecal analgesia.

• Epinephrine hastens the onset of analgesia and increases its duration of action. Thus, it decreases the requirement of higher concentration of local anesthetics.

• Unfortunately, when local anesthetics are used in combination with epinephrine, they are more highly associated with motor block, even if the concentration of the local anesthetic is unchanged. ^[16] This higher association with motor blockage and its potential tocolytic effects has made epinephrine less popular for neuroaxial use.

See the list below:

• Crystalloid, 500-1000 mL

• Equipment to monitor blood pressure, maternal heart rate, and fetal heart rate

• Drapes, antiseptic

• Epidural needle, 17-18 gauge (ga)

• Epidural catheter

• Anesthetic (see Anesthesia section above)

• Preservative-free saline, 3-5 mL

• Single-orifice or multiple-orifice catheter.

  • The proposed advantage of single-orifice, open-ended catheters is that the injection of drugs is restricted to a single anatomical site. In theory, this should facilitate the detection of intravenous or subarachnoid placement of catheter. Likewise, the purported disadvantage of multiple-orifice, closed-end catheters is that local anesthetic may be injected into more than one anatomical site.

  • However, increasing evidence suggests that multiple-orifice, closed-end catheters result in a more even distribution of local anesthetic and a greater likelihood of successful epidural anesthesia.

  • Modern catheters (single- and multiple-orifice) are soft, flexible, and reliable, so there are no compelling reasons to favor one over another, provided the anesthesiologist pays careful attention to detail during the injection of local anesthetic.

Pregnant women have exaggerated lumbar lordosis (see the image below), which makes it more difficult for them to flex the lumbar spine. However, as most pregnant women are relatively young, their spines have sufficient flexibility to facilitate the insertion of a needle into the epidural or subarachnoid space.

Regional anesthesia can be administered with the patient in either a seated or lateral decubitus position.

• The seated position is especially preferred for obese patients and to facilitate instrument delivery. Its advantages include facilitating identification of the spinous process, providing better respiratory mechanism, and improving maternal comfort. However, the seated position is more likely associated with an increased incidence of orthostatic hypotension. An assistant often is required while using the seated position.

• The advantages of lateral positioning include better uteroplacental perfusion, lower likelihood of orthostatic hypotension, and facilitation of fetal heart rate monitoring during placement of the epidural catheter. In addition, some patients find this position more comfortable.

When regional analgesia is performed with the patient in the lateral position, the patient’s back should lie parallel to the edge of the bed for the following 2 reasons:

• First, the edge is the firmest section of the mattress. If the patient lies away from the edge of the bed, the patient’s weight depresses the mattress, and the anesthesiologist must work in a downhill direction.

• Second, this position allows the anesthesiologist to keep his or her elbows flexed, which facilitates control of fine hand and wrist muscle movements. This is particularly important when using the loss of resistance technique for performing epidural anesthesia. Every attempt should be made to avoid a tight fetal curl position while the mother is lying in lateral decubitus position for identification of the epidural space.

When administering a hyperbaric local anesthetic solution while the patient is in the lateral position, posture has more influence on the spread of spinal analgesia than epidural anesthesia.

• When administering a spinal block while the patient is in lateral position, injecting local anesthetic with the patient lying on her right side makes sense because she will be tilted leftward thereafter. If the local anesthetic is injected with the patient lying on her left side, and the leftward tilt is maintained thereafter, an asymmetric inadequate block may result.

• Posture has less influence on the spread of epidural anesthesia. During epidural anesthesia, a unilateral block more often results from malposition of the catheter than from prolonged use of one position.

Aortocaval compression must be avoided at all times. The gravid uterus can occlude the inferior vena cava and aorta when the parturient assumes the supine position. This can decrease uteroplacental perfusion, even in the absence of anesthesia.

The preanesthetic evaluation requires a focused history and physical examination before providing regional analgesia. This should include a maternal health and anesthetic history; a relevant obstetric history; a baseline blood pressure measurement; and an airway, heart, lung, and back examination. Recognition of significant anesthetic or obstetric risk factors should encourage consultation between the obstetrician and the anesthesiologist. Besides these obstetric and anesthetic risk factors, progress of labor and the sources available at the facility help determine the appropriate type of regional block.

• Although intravenous fluid preloading may be used to reduce the frequency of maternal hypotension, initiation of regional analgesia should not be delayed to administer a fixed volume of intravenous fluid.

• An intrapartum platelet count is not routinely necessary before administration of regional anesthesia in an uncomplicated healthy parturient. ^[4] However, certain groups of patients may benefit from such evaluations, including those with severe preeclampsia, HELLP syndrome, idiopathic thrombocytopenic purpura, known placental abruption, or other risk factors for disseminated intravascular coagulation.

• A routine blood crossmatch is not necessary for a healthy and uncomplicated parturient before vaginal or operative delivery. The decision to order or require a blood type and screen or crossmatch should be based on maternal history, anticipated hemorrhagic complications, and local institutional policies.

• The oral intake of modest amounts of clear liquids may be allowed for uncomplicated laboring patients. ^[17] The volume of liquid ingested is less important than the presence of particulate matter in the liquid ingested. Patients with additional risk factors for aspiration (eg, morbid obesity, diabetes, difficult airway) or patients with increased risk for operative delivery may have further restrictions of oral intake, determined on a case-by-case basis. Solid foods should be avoided in all laboring patients.

The 3 major subtypes of regional block are epidural, combined spinal/epidural (CSE), and spinal. Of these, the epidural technique is most preferred for labor analgesia. See Table 1 below for a comparison of epidural and spinal techniques.

Table 1. Clinical Features of Epidural and Spinal Block (Open Table in a new window)

Epidural analgesia

Epidural analgesia is the most effective form of pain relief in labor ^{[18, 19, 20, 21, 22, 23, 24]} and is used by most laboring women in United States. ^[25] It has 4 subtypes.

• Single epidural shot

  • The single shot technique is not usually practiced for labor analgesia because it is short lasting.

  • Unlike the other 3 subtypes, insertion of an epidural catheter is not necessary for this technique.

• Intermittent bolus

  • The intermittent bolus technique, although still used, is currently out of favor.

  • This technique has 2 limitations. First, if injections are not administered until pain returns, the parturient experiences intervals of analgesia after the dose takes effect alternating with intervals of pain as the analgesia wanes. Second, intermittent dosing requires frequent provider intervention.

• Continuous infusion epidural

  • Continuous infusion of analgesics into the epidural space avoids the peaks and valleys of intermittent administration and results in a smoother analgesic experience for the parturient with fewer provider interventions. It is also associated with less motor block and hypotension.

  • The infusion may be adjusted to individualize analgesia, and additional rescue doses may be administered, as needed. In addition, the epidural catheter can also be used if a larger dose of local anesthetic is needed for instrumental or cesarean delivery or for pain control postpartum.

• Patient-controlled epidural analgesia (PCEA)

  • PCEA differs from the continuous infusion technique in that the parturient herself is given the means to fine-tune the dose of analgesic she receives. This gives the parturient the psychological advantage of being in control of her own therapy. This technique is best reserved for patients who are willing and able to understand that they are in control of their analgesia.

  • Compared to continuous epidural infusion, PCEA results in a lower total dose of local anesthetics used over the course of labor, ^[26] a decreased need for the physician to administer additional doses of anesthetic, and a lower incidence of motor block. ^[27]

  • The most common clinical PCEA technique is administration of local anesthetics with fentanyl at a basal infusion rate at 6-9 mL/h, with 5-mL bolus doses with a 10-15 minute lockout period. Some recommend a continuous background infusion with superimposed PCEA, whereas others use a pure PCEA approach without background infusion. See Table 2 below for sample regimens.

  • New approaches to administering PCEA have been suggested, such as using automated mandatory boluses instead of a continuous background infusion to decrease analgesic consumption.

Epidural analgesia administration

Obtain informed consent.

Ensure adequate venous access.

Prehydrate with 500-1000 mL of crystalloid.

Set up patient monitoring as follows:

• Blood pressure recording at baseline prior to administration of regional anesthetics; then every 1-2 minutes for 15 minutes after giving a bolus of local anesthetic; then at every 5-15 minute interval until the block wears off

• Continuous maternal heart rate monitoring during induction of analgesia

• Continuous fetal heart rate monitoring

Help the patient assume a seated or lateral decubitus position. The seated position is preferred in very obese patients.

Clean the lumbar area with appropriate antiseptic and drape the area.

Palpate the lumbar spinous process and choose the widest interspace below L3.

Place a hollow epidural needle (17 or 18 ga) in the intervertebral ligaments.

• These ligaments are characterized by a high degree of resistance to penetration.

• Connect a syringe to the epidural needle. Resistance upon injection confirms placement in the ligaments.

Slowly advance the needle while feeling for resistance. A sudden loss of resistance is felt as the epidural needle enters the epidural space.

Aspirate for blood or cerebrospinal fluid (CSF).

Most anesthesiologists insert the catheter before injecting the therapeutic dose of local anesthetic so that correct catheter placement can be verified promptly. If this catheter technique is chosen, administer 3-5 mL of preservative-free normal saline or dilute local anesthetic to facilitate passage of the catheter. Some anesthesiologists contend that this expands the epidural space and decreases the likelihood of unintentional intravenous cannulation of the catheter.

Advance an epidural catheter into the epidural space.

• To minimize the risk of catheter displacement, especially in obese patients, insert the catheter at least 4 cm into the epidural space.

• Shallow placement (2 cm for single-orifice catheters; 3 cm for multiple-orifice catheters) increases the likelihood of block failure. Deep placement increases the chance of intravenous placement, unilateral block, or both.

Withdraw the needle over the tubing.

After careful aspiration and uterine contraction, inject a test dose of 3 mL of lidocaine 1.5% with epinephrine 1:200,000 or 3 mL of bupivacaine 0.25% with epinephrine 1:200,000. This minimizes the chance of confusing tachycardia caused by labor pain with tachycardia caused by intravenous injection of the test dose.

If the test dose is negative (ie, absence of tachycardia), inject the anesthetic in 2-3 small boluses to achieve a cephalad sensory level of approximately T10. Initial block options include the following:

• Bupivacaine 0.125-0.25% (10-15 mL)

• Bupivacaine 0.125% (10-15 mL) with fentanyl 50-100 mcg

• Fentanyl 50-100 mcg (or sufentanil 10-15 mcg) in 10 mL normal saline

After 15-20 minutes, assess sensation using loss of sensation to cold or pinprick.

• If no block is evident, replace the catheter.

• If the block is asymmetrical, withdraw the catheter 0.5-1 cm and inject an additional small dose of the anesthetic.

• If the block remains inadequate, replace the catheter.

When loss of sensation is confirmed, secure the catheter to the patient’s back with adhesive dressing.

After administration of analgesic, position the patient in a lateral or semilateral position to avoid aortocaval compression.

Solutions of a local anesthetic, opioids, or a combination of the two can now be administered through the catheter. Aspirate the catheter for blood or CSF before each top-up dose. Subsequent analgesia options include:

• Repeated intermittent boluses as necessary to maintain maternal comfort

• Continuous infusion of 10-15 mL/h of one of the following:

  • Bupivacaine 0.0625-0.125% with fentanyl 1-2 mcg/mL (or sufentanil 0.1-0.3 mcg/mL)

  • Bupivacaine 0.125-0.25% without opioids

  • Addition of epinephrine 1:400,000 (2.5 mcg/mL) to either of above

• PCEA as shown in Table 2 below

Assess the level of analgesia and intensity of motor block at least hourly. Development of motor block may indicate subarachnoid migration. Verify catheter location by aspiration, careful sensory motor examination, and, if necessary, cautious administration of a test dose.

Achieving adequate perineal analgesia is especially important in women in whom episiotomy or the application of forceps is probable.

• Women who progress into the second stage of labor soon after induction of epidural analgesia seldom have adequate sacral blockade and often require additional epidural boluses of local anesthetic before delivery. On the other hand, women who have been receiving continuous epidural analgesia for many hours often have excellent perineal analgesia at delivery.

• Reports of rectal pressure with progressive descent of the fetal head may indicate that sacral analgesia is inadequate for delivery.

• If perineal anesthesia is required, administer 10-15 mL of local anesthetic such as lidocaine.

• Be aware that the incidence of third- and fourth-degree perineal laceration is increased in patients who receive epidural analgesia (odds ratio [OR], 1.7).

When epidural analgesia is discontinued, remove the catheter with utmost care. If resistance is encountered while removing the catheter, the patient should assume a position that reduces lumber lordosis. This often lessens the kinking of the catheter between perivertebral structures.

Following successful catheter removal, ensure that the tip is present, indicating complete removal. If the catheter breaks, leaving part of the catheter in the patient, some physicians may favor aggressive attempts to remove the broken catheter but most do not. Neurosurgical consultation can be obtained to discuss the risk and benefit of leaving part of the sterile catheter alone versus surgical removal. In most cases, the patient can be informed of the complications and observed over time, as the incidence of catheter migration or other delayed sequelae appears to be low. When necessary, CT may help locate the broken catheter.

Table 2. Regimens for PCEA (Open Table in a new window)

Combined spinal/epidural analgesia

The combined spinal/epidural method has recently gained increased popularity. It is otherwise called the needle-through-needle or coaxial technique.

This technique comes into play in specific circumstances, such as late first stage or second stage of labor, where the prolonged latency of epidural analgesia may be unacceptable.

Advantages of this method include rapid and effective analgesia, no increase in adverse effects, continued ambulation during labor (in up to 80% of women) because not associated with impaired equilibrium, ^{[28, 29]} low incidence of hypotension, and a combination of the benefits of spinal and epidural blocks.

Be aware that when intrathecal drugs are administered prior to placing the epidural catheter, confirming the correct placement of the catheter may be difficult. Although unlikely, this could be a potential problem, should the epidural catheter be needed later for providing anesthesia in emergency situation (eg, cesarean delivery).

Combined spinal/epidural analgesia administration

This technique avoids multiple skin punctures.

Obtain informed consent.

Assure adequate venous access.

Prehydrate with 500-1000 mL of crystalloid.

Set up patient monitoring as follows:

• Blood pressure recording at baseline prior to administration of regional anesthetics; then every 1-2 minutes for 15 minutes after giving a bolus of local anesthetic; then at every 5-15 minute interval until the block wears off

• Continuous maternal heart rate monitoring during induction of analgesia

• Continuous fetal heart rate monitoring

Help the patient assume a seated or lateral decubitus position. The seated position is preferred in very obese patients.

Clean the lumbar area with appropriate antiseptic and drape the area.

Palpate the lumbar spinous process and locate the L3-4 or L4-5 spinal level.

Place a hollow epidural needle (17 or 18 ga) in the intervertebral ligaments.

• These ligaments are characterized by a high degree of resistance to penetration.

• Connect a syringe to the epidural needle. Resistance upon injection confirms placement in the ligaments.

Slowly advance the needle while feeling for resistance. A sudden loss of resistance is felt as the epidural needle enters the epidural space.

Place a long spinal needle (≤24 ga and ≥124 mm) into the subarachnoid space through the epidural needle.

The spinal needle should extend 10-15 mm beyond the tip of the epidural needle. The spinal needle can be used to confirm the position of epidural needle, which may help prevent unintentional dural puncture with the epidural needle.

Withdraw the spinal needle after a single bolus of opioid into the subarachnoid space. In this bolus, the opioid is sometimes in combination with a local anesthetic.

Place an epidural catheter to permit administration of continuous or repeated doses of analgesics.

For labor analgesia, an opioid such as fentanyl 10-25 mcg or sufentanil 2.5-10 mcg may be injected alone or with a local anesthetic such as isobaric bupivacaine 1-2.5 mg into the intrathecal space. This combination of fentanyl with bupivacaine provides analgesia for approximately 90 minutes.

If prolonged analgesia is indicated, after the effects of spinal drugs wear off, initiate an epidural infusion with a bolus of bupivacaine 0.0625-0.125% with fentanyl (2 mcg/mL) or an equivalent dose of ropivacaine.

Spinal analgesia

Spinal (ie, subarachnoid, intrathecal) block is used less often than epidural block for labor analgesia because it is short-lasting and can’t extend the duration of action. It does have certain advantages over epidural analgesia, including a short procedure time, rapid onset of the block, and high success rate.

Spinal block plays a role for procedures of limited duration, such as forceps or vacuum delivery, or for patients already in advanced labor.

If labor is expected to last longer than the analgesic effects of the chosen spinal drugs, or if operative vaginal delivery is likely, a catheter technique for continuous spinal anesthesia may be considered.

Spinal analgesia administration

Obtain informed consent.

Assure adequate venous access.

Prehydrate with 500-1000 mL of crystalloid.

Set up patient monitoring as follows:

• Blood pressure recording at baseline prior to administration of regional anesthetics; then every 1-2 minutes for 15 minutes after giving a bolus of local anesthetic; then at every 5-15 minute interval until the block wears off

• Continuous maternal heart rate monitoring during induction of analgesia

• Continuous fetal heart rate monitoring

Help the patient assume a seated or lateral decubitus position. The seated position is preferred in very obese patients.

Clean the lumbar area with appropriate antiseptic and drape the area.

For the spinal block, the subarachnoid space can be entered by either a midline or a paramedian approach. For most patients, the midline approach is faster and less painful than the paramedian approach. Nevertheless, the paramedian approach is a useful technique that allows successful identification of the subarachnoid and epidural spaces in difficult cases. The more commonly practiced midline approach requires the patient to reduce the lumbar lordosis to allow access to the subarachnoid space between adjacent spinous processes (usually L2-3 or L3-4).

Inject local anesthetic both intradermally and subcutaneously at this site.

Insert the introducer needle, directed midline, into the substance of the interspinous ligament.

Hold the introducer steady with one hand while the other hand holds the spinal needle like a dart. Use the fifth finger as a tripod against the patient’s back to prevent patient movement from causing the needle to insert to a level deeper than intended.

The introducer needle allows more accurate introduction of the spinal needle than is possible with use of a small gauge spinal needle alone. Most anesthetists use a 24- to 27-ga spinal needle, preferably the pencil point needles (eg, Whitacre, Sprotte), to avoid postdural puncture headache (PDPH). These pencil point needles may be inserted without attention to the dural fiber direction.

Note the sudden loss of resistance as the needle passes through the ligamentum flavum and the dura.

Remove the stylet. CSF is expected to appear in the needle hub.

• If it does not, rotate the needle in 90° increments until CSF appears.

• If CSF does not appear in any quadrant, replace the stylet, advance the needle a few more millimeters, and check again for CSF flow.

• If CSF still does not appear and the needle is at an appropriate depth for the patient, withdraw both the needle and the introducer and repeat the process.

The most common reason for lack of CSF flow is insertion of the needle away from the midline. Significant pain often suggests this incorrect placement of needle. Indeed, a patient often indicates that the pain is located on either the left or right side of the back. In such cases, correct direction of the needle should be confirmed. Redirection of the needle often eliminates the patient’s pain and results in the successful identification of the intrathecal space.

Once CSF is freely dripping from the needle hub, use the dorsum of the nondominant hand to steady the introducer and the spinal needle against the patient’s back while the syringe with local anesthetic is attached to the needle.

Aspirate to ensure free flow of CSF.

Inject the anesthetic drug at a rate of 0.2 mL/s.

Usual spinal block is achieved by injecting 25-50 mg of hyperbaric lidocaine or 5-7.5 mg of hyperbaric bupivacaine into the subarachnoid space. Fentanyl 10-25 mcg may also be added to the spinal anesthetic.

Anesthetic drugs are preferably administered after a uterine contraction to decrease the likelihood of unexpected high block.

After the completion of injection, again aspirate approximately 0.2 mL of CSF and reinject that CSF back into the intrathecal space. This last step reconfirms the needle location and clears the needle of the remaining local anesthetic.

Position the patient as appropriate. A dorsal supine position with a leftward tilt is preferred.

The level of spinal block is usually complete and fixed in 5-10 minutes, but it may continue to creep upward for up to 20 minutes.

See the list below:

• Fasting during labor and delivery is strongly recommended, with the exception of clear liquids, to avoid what it known as Mendelson syndrome from aspiration of acidic stomach contents.

• Delaying the administration of epidural analgesia until labor is well established is reasonable. However, withholding analgesia until the patient has achieved an arbitrary cervical dilatation during the first stage of labor is unnecessary. In fact, timing of epidural placement has no effect on cesarean rate, fetal malposition, or forceps delivery. ^{[30, 31]}

• Early placement of spinal or epidural catheter for obstetric (eg, attempted vaginal birth after cesarean delivery) or anesthetic indications should be considered to reduce the need for general anesthesia if an emergency procedure becomes necessary.

• Local anesthetics are divided into 2 classes: amides and esters. Amides include lidocaine, bupivacaine, and ropivacaine. Esters include tetracaine, chloroprocaine, and procaine. True allergic reaction to either subclass of local anesthetic is rare. When a patient reports that she is allergic to local anesthetics, she is frequently referring to a normal reaction to the epinephrine sometimes added to the local anesthetics. If a specific local anesthetic allergy is identified, choose a local anesthetic from the other class. For a complete discussion of local anesthetics, see Medscape Reference article Infiltrative Administration of Local Anesthetic Agents.

• Walking epidurals have been the object of much recent focus. One of the goals has been to allow the patients to ambulate, or at least achieve greater ease in patient care and greater patient satisfaction with increased mobility. However, the benefits of walking epidural on progress of labor remain poorly documented and controversial.

• Delayed pushing in the second stage of labor may result in an increased likelihood of spontaneous vaginal delivery. ^[32] On the other hand, early pushing often results in maternal exhaustion and frequent variable decelerations. Thus, allowing uterine contractile force to do most of the work in promoting the descent of the fetal head seems reasonable. Obstetricians should also be encouraged to avoid an arbitrary termination of the second stage of labor.

• During local anesthetic administration, consider the following steps to avoid unintentional intravenous or intrathecal administration:

  • Lower the catheter below the level of insertion to check for passive return of cerebrospinal fluid (CSF) or blood.

  • Aspirate prior to injecting each dose of local anesthetic.

  • Administer the epidural test dose after a uterine contraction.

  • Use dilute solutions of local anesthetic for labor analgesia.

  • Avoid using more than 5 mL of local anesthetic as a single bolus.

  • Maintain verbal contact with the patient.

  • If little or no block results from local anesthetic administration, assume that the local anesthetic was injected intravenously and remove the catheter.

Serious toxicity from labor analgesia usually follows inadvertent intravenous injection, but it also may be induced by administration of excessive amounts of anesthetic. It generally manifests in the central nervous and cardiovascular systems. For both systems, the early symptoms are those of stimulation followed by depression as blood levels rise.

• An epidural test dose often helps reduce the complications associated with epidural analgesia.

  • The choice of drugs for the test dose is controversial. A typical test dose is 3 mL of either lidocaine 1.5% with epinephrine 1:200,000 (ie, lidocaine 45 mg and epinephrine 15 mcg) or bupivacaine 7.5-12.5 mg with epinephrine. Inject the test dose to exclude intravascular or intrathecal placement after placement of the epidural catheter.

  • If the test dose is injected intravascularly, the lidocaine produces tinnitus, circumoral numbness, metallic taste, and dizziness, and the beta1-adrenergic agonist effect of epinephrine results in tachycardia. The tachycardia (heart rate increase by 10 bpm) is seen within 60 seconds of the test dose and lasts for nearly 60 seconds. The subjective sensation of palpitation itself is also a reliable symptom of intravascular administration, irrespective of the monitored heart rate. However, the wide variations in heart rate that occur with labor pain may mask epinephrine-induced increases in heart rate. Thus, to maximize sensitivity, the test dose should be administered immediately after a uterine contraction.

  • Intrathecal injection of the test dose causes rapid onset of dense lower extremity motor block and sacral analgesia. For assessment of motor function of lower extremity, some recommend a straight-leg raising test 4 minutes after the injection of test dose.

  • Air may be used for the test dose as an alternative to local anesthetic with epinephrine. Intravascular injection of 0.5-1 mL of air is easily confirmed by a characteristic swishing sound heard during Doppler monitoring of the maternal precordium. This technique may be useful in selected patients in whom even small amounts of intravenous epinephrine are contraindicated. Aspiration alone is not a reliable method for checking correct placement.

  • The lower concentration of local anesthetics currently used for epidural analgesia techniques for labor are unlikely to cause untoward effects if they are accidentally injected intravascularly or intrathecally. Furthermore, the introduction of softer, more flexible epidural catheters has decreased the risk of venous cannulation from 5.7% to 1.1%. ^[33] Therefore, some anesthesiologists have abandoned the test dose when low concentrations of local anesthetics are used.

• Cardiovascular toxicity may include hypertension, tachycardia, cardiac arrhythmia, cardiac arrest, or (commonly) hypotension.

  • Hypotension, a common complication, develops soon after injection of local anesthetics. Because of the speed of the onset of regional block, it is seen more often with spinal block (25-67%) than with epidural block (8.5-9% in women with prior hydration or fluid bolus; 28-31% in women without prehydration). ^{[23, 34, 35, 36, 37]} In patients with diminished intravascular volume (eg, preeclampsia, antepartum bleeding, dehydration) regional block is more highly associated with hypotension. Use of opioids alone usually does not produce hypotension. Recent use of ultra low dose of local anesthetics has lowered the incidence of hypotension. ^[38]

  • The precise definition of hypotension in this setting is controversial; criteria include a 20% reduction in mean arterial pressure from baseline or a systolic blood pressure < 100 mm Hg. Hypotension is the consequence of sympathetic blockade compounded by obstructed venous return from uterine compression of inferior vena cava and adjacent large veins along with dilatation of vascular beds. A secondary mechanism may be the decreased maternal endogenous catecholamines following pain relief. This decrease in blood pressure could be severe enough to require treatment in one third of patients needing epidural analgesia.

  • Treatment includes oxygen administration, maternal repositioning, uterine displacement, intravenous hydration, and intravenous injection of ephedrine (5-10 mg) or phenylephrine (100 mcg). Rapid fluid boluses should not contain dextrose because maternal hyperglycemia causes insulin release with associated subsequent neonatal hypoglycemia. Several investigators have shown that when the hypotension associated with regional anesthesia is promptly corrected, it has no effect on the newborn.

• Central nervous system toxicity may include dizziness, tinnitus, metallic taste, numbness of tongue and mouth, slurred speech, bizarre behavior, muscle fasciculation and excitation, convulsion, or loss of consciousness.

• Postdural puncture headache (PDPH) most likely results from cerebral vasodilatation or from the traction of cranial structures due to leakage of cerebrospinal fluid from the site of dural puncture. It occurs with similar frequency with each method of analgesia (spinal block, 1.5-3%; epidural block, 2%; combined spinal/epidural [CSE], 1-2.8%).

  • Inadvertent dural puncture during the placement of an epidural catheter occurs in about 1-3% percent of parturient women; ^[39] nearly 70% of these women experience severe headache. ^[40] During spinal block, this complication could be avoided by using small gauge, pencil point spinal needles, ^[41] and by restricting the number of spinal punctures.

  • No good evidence indicates that bed rest, abdominal binder, and lying in prone position are effective in preventing PDPH. Vigorous hydration may be of value but is without compelling evidence to support its use. Mild persistent headache is treated with analgesics, caffeine, and theophylline.

  • An epidural blood patch is recommended for severe headache and is effective 75-90% of the time. ^{[42, 43]} For autologous blood patch, 15-20 mL of the patient’s fresh blood is injected into the epidural space, preferably at the site of dural puncture. The relief is immediate and complications are minimal. After the blood patch, the patient should avoid coughing and straining for several days.

  • If the headache does not have the pathognomonic postural characteristics or persists despite treatment with a blood patch, other diagnoses must be considered and appropriate testing performed. Common differential diagnoses include infection, migraine headache, pneumocephalus, cortical vein thrombosis, preeclampsia, and intracerebral or subarachnoid hemorrhage.

• Pruritus is a commonly seen with regional opioid administration. It is more likely to occur with spinal or CSE block (41-85%) than with epidural block alone (1.3-26%).

  • The etiology appears to be modulation of nociceptive reception, not histamine release. Thus, treatment with antihistamines such as diphenhydramine is not indicated, although antihistamines are often used for soporific effects.

  • The ideal treatment for this pruritus is a small intravenous dose of an opioid antagonist such as naloxone (40-100 mcg) or the opioid agonist-antagonist nalbuphine (5-10 mg). Other suggested intravenous doses include diphenhydramine 25 mg, propofol 10 mg, and droperidol 0.625 mg.

• Nausea and vomiting occur commonly in laboring patients as an accompaniment of visceral pain.

  • Neuroaxial analgesia block effectively diminishes or eliminates this visceral pain but can also precipitate nausea and vomiting. The mechanism is a decrease in blood pressure affecting the area postrema in the medulla or the cephalad spread of opioids to chemoreceptor trigger zone.

  • The optimal treatment includes administration of an opioid antagonist and correction of hypotension when associated. In particular, naloxone 40-100 mcg IV, droperidol 0.625 mg IV, or metoclopramide 5-10 mg IV can be used. Ondansetron, dolasetron, or propofol are also used.

• The associations between back pain and epidural analgesia are unclear.

  • Chronic back pain has been shown to be associated with epidural analgesia in retrospective studies. ^[44] On the contrary, prospective cohort studies and one small, randomized controlled trial have found no significant association. ^{[45, 46, 47, 48, 49, 50, 51]}

  • Local tenderness at the site of epidural or spinal placement and transient backache are relatively common, particularly if placement of the block was difficult. This usually clears within several days to 3 weeks and may be related to superficial irritation of the skin or periosteal irritation or damage.

  • Postpartum backache may also be related to hormonal changes, softening of maternal ligaments, and mechanical changes (eg, exaggerated lumber lordosis, maternal weight gain).

  • Although short-term back pain is common, it does not appear to be related to the use of regional analgesia. Similarly, no causal relationship exists between the use of epidural analgesia and the development of long-term postpartum backache.

• Labor is slightly prolonged with epidural analgesia. ^{[18, 23, 52, 53]}

  • The first stage is prolonged by nearly 30 minutes, and the second stage by 15 minutes.

  • The prolongation of the second stage of labor increases the need for instrumental delivery (odds ratio [OR], 2.1). ^[54] However, the reason for this increase with epidural remains unexplained. The most likely explanations include motor blockade preventing the mother from pushing, a lower threshold for instrumental delivery, and an association of higher frequency of persistent occipitoposterior presentation. ^[3] The rate of cesarean delivery remains unchanged. ^[54]

  • Use of oxytocin during labor is increased in the presence of epidural block (OR, 2.8).

• Fetal bradycardia occurs in 8% of cases.

  • Fetal bradycardia after induction of regional analgesia may result from decreased cardiac output, decreased uterine perfusion, or uterine tetany caused by maternal hypotension. ^[55] Rapid onset of analgesia may cause sudden decrease in plasma epinephrine concentration and its relaxant effects on the myometrium and can result in uterine tetany.

  • To treat abnormalities noted in fetal heart rate, administer oxygen and attempt to correct hypotension in the mother. The mother should be in the left lateral position to avoid aortocaval compression. Nitroglycerin 50-200 mcg IV or 400-800 mcg SL can be used to improve the oxygenation and heart rate of the fetus; alternatively, terbutaline 0.25 mcg SC can be administered to treat uterine hyperactivity.

• Fever, in association with epidurals, ^{[56, 57]} is seen more often in nulliparous women (19% of nulliparous women, 1% of multiparous women). ^[58] The incidence is nearly 24% per some studies. ^[58] The odds ratio of fever incidence is 5.6.

  • The association of fever with epidural analgesia is complex. Some authors attribute it to placental infection, whereas others believe it to be noninfectious.

  • Both randomized and observational studies have demonstrated that the neonates of women who received epidural analgesia are more likely to be evaluated and treated with antibiotics because of concern about infection. ^[59] In fact, neonates born to mothers who receive epidural analgesia are not at increased risk of sepsis. ^[59] For mothers, it may be appropriate to discontinue antibiotics if temperature returns to normal within a few hours of delivery and in the absence of other obvious sources of infection.

• Breastfeeding success does not depend on the use of regional analgesia. ^{[4, 60]}

• Respiratory depression is a serious adverse effect that can occur with spinal or epidural analgesia.

  • Clinical experience with hydrophobic opioids (eg, morphine) suggests a biphasic respiratory depression; the immediate phase is caused by rapid achievement of serum level, whereas the more serious respiratory depression that occurs 6-8 hours later is because of increased CSF levels.

  • Although it is still prudent to monitor for 24 hours after epidural or intrathecal morphine, the risk period probably does not extend beyond 12 hours. In contrast, the lipid-soluble opioids (fentanyl and sufentanil) require monitoring for only 2 hours. Treatment includes administration of naloxone 40-100 mcg IV or more, as needed.

• A relationship has been suggested between epidural morphine and herpes labialis outbreak. Whether reactivation of herpes labialis follows spinal analgesia is not known.

• Urinary retention during labor is not uncommon, but it appears to be more likely with regional analgesia. ^[61] Patients in labor and postpartum should be observed for possible bladder distension, particularly when associated with suprapubic pain during uterine contraction. Urinary retention during labor is treated with catheterization; intravenous administration of naloxone 400-800 mcg may be necessary.

• Inadequate or failed block happens more often with epidural than spinal block. The failure rate is as high as 2-5%. In 10-15% of cases, the pain relief is incomplete. ^[62] The high failure rate may be related to the inexperience of practitioners or rapid progression of labor.

  • When the correct placement of an epidural catheter is in doubt, inject 10-15 mL of more concentrated local anesthetic (eg, lidocaine 1.5%) in divided doses to verify placement. If this does not promptly provide significant analgesia, the epidural catheter should be replaced without prolonged attempts to verify placement.

  • A unilateral epidural block is attributed to obstruction in epidural space, anatomical causes, patient position (prolonged time on one side), or excessive catheter length in epidural space. Withdrawal of the catheter by 0.5-2 cm and injection of a larger volume of dilute local anesthetic usually solves this problem. If these steps do not resolve the problem, replace the catheter.

  • If the patient feels pain because of a change in the nature of her labor while the catheter is still in place, evaluate the progress of labor and check for bladder distension. To increase analgesia, the volume or concentration of the local anesthetic can be increased or an opioid can be added to the solution. Before adding an opioid, ensure that the catheter was properly placed and has not been dislodged. Do not add an opioid to avoid having to replace a misplaced catheter.

• Dense or prolonged epidural block can occur rarely after long continuous infusions or repeated bolus dosing.

  • The increasing use of dilute local anesthetics has decreased the incidence of prolonged or dense block. The resulting significant motor blockade can be bothersome to the patient and the nursing staff. This may also make the voluntary maternal expulsive efforts more difficult during the second stage of labor and lead to prolonged epidural blocks in the postpartum period, particularly if epinephrine is added to the anesthetic solution.

  • Dense epidural block can be managed by decreasing the epidural infusion rate or by decreasing the concentration of local anesthetic. If the block is still bothersome, discontinuing the infusion for 30 minutes may be helpful, followed by restarting the infusion with more dilute local anesthetic solutions.

  • The differential diagnosis includes epidural hematoma. A block that is unilateral, is not associated with backache, or slowly regresses and does not progress, would argue against an epidural hematoma.

• High spinal block

• Chemical meningitis or epidural abscess or hematoma

• Infant outcomes

  • No difference is observed in 5-minute Apgar score < 7.

  • No difference is observed in cord blood pH level.

The American College of Obstetricians and Gynecologist (ACOG) has issued recommendations regarding use of regional analgesia in patients using anticoagulants. ^[10]

• Patients using therapeutic unfractionated heparin should be able to use regional analgesia in the presence of normal activated partial thromboplastin time (aPTT).

• Therapeutic unfractionated heparin should be stopped the night before planned induction or cesarean delivery or with the onset of spontaneous labor.

• A prophylactic dose of unfractionated heparin or aspirin is not a contraindication for use of regional analgesia.

• If therapeutic anticoagulation with intravenous unfractionated heparin is required in patients who recently have had epidural catheterization, heparin should not be given for at least 1 hour after the epidural catheter has been inserted or removed.

• In patients receiving intravenous heparin, the epidural catheter may be removed 2-4 hours after the last dose of heparin, after the patient’s coagulation status has been evaluated.

• Since heparin-induced thrombocytopenia may occur in patients receiving heparin for more than 4 days, a platelet count should be assessed prior to regional block or epidural catheter removal.

• Women receiving a once-daily prophylactic dose of low molecular weight heparin (LMWH) need to wait 12 hours after the last dose prior to receiving regional analgesia.

• The use of regional analgesia in women receiving twice-daily therapeutic LMWH has not been studied sufficiently, and whether waiting 24 hours from the last heparin dose is adequate is unknown.

• If the patient has an indwelling epidural catheter, LMWH should be withheld for at least 2 hours after the removal of the epidural catheter.

• An epidural catheter should not be removed for at least 10-12 hours after the last dose of LMWH.

• If postoperative LMWH is to be used, the first dose of a twice-daily dosing regimen should not be administered prior to 24 hours postoperatively. If postoperative LMWH is to be used, the first dose of a once-daily dosing regimen should not be administered prior to 6-8 hour postoperatively. If blood is seen during administration of spinal or epidural analgesia, LMWH should not be administered for the first 24 hours postoperatively, even if a once-daily dosing regimen is planned.

• In patients receiving warfarin (Coumadin), regional block should not be performed until aPPT and INR are normal.

• If LMWH prophylaxis must be instituted in the presence of an indwelling epidural catheter, low-dose epidural technique should be used to permit careful monitoring of neurological function.