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Pain Pathways during Labor
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The pain of labor arises from contraction of the myometrium against the resistance of the cervix and perineum, progressive dilation of the cervix and lower uterine segment, and stretching and compression of pelvic and perineal structures.
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Pain during the first stage of labor is primarily visceral pain resulting from uterine contractions and cervical dilation. It is usually initially confined to the T11-T12 dermatomes during the latent phase, but eventually involves the T10-L1 dermatomes as labor enters the active phase. The visceral afferent fibers responsible for labor pain travel with sympathetic nerve fibers first to the uterine and cervical plexuses, then through the hypogastric and aortic plexuses, before entering the spinal cord with the T10-L1 nerve roots. The pain is initially perceived in the lower abdomen but may increasingly be referred to the lumbosacral area, gluteal region, and thighs as labor progresses. Pain intensity also increases with progressive cervical dilation and with increasing intensity and frequency of uterine contractions. Nulliparous women and those with a history of dysmenorrhea appear to experience greater pain during the first stage of labor.
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The onset of perineal pain at the end of the first stage signals the beginning of fetal descent and the second stage of labor. Stretching and compression of pelvic and perineal structures intensifies the pain. Sensory innervation of the perineum is provided by the pudendal nerve (S2-4) so pain during the second stage of labor involves the T10-S4 dermatomes.
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Nearly all parenteral opioid analgesics and sedatives readily cross the placenta and can affect the fetus. Concern over fetal depression limits the use of these agents to the early stages of labor or to situations in which regional anesthetic techniques are not available or appropriate. Central nervous system depression in the neonate may be manifested by a prolonged time to sustain respirations, respiratory acidosis, or an abnormal neurobehavioral examination. Moreover, loss of beat-to-beat variability in the fetal heart rate (seen with most central nervous system depressants) and decreased fetal movements (due to sedation of the fetus) complicate the evaluation of fetal well-being during labor. Long-term fetal heart rate variability is affected more than short-term variability. The degree and significance of these effects depend on the specific agent, the dose, the time elapsed between its administration and delivery, and fetal maturity. Premature neonates exhibit the greatest sensitivity. In addition to maternal respiratory depression, opioids can also induce maternal nausea and vomiting and delay gastric emptying. Some clinicians have advocated use of opioids via patient-controlled analgesia (PCA) devices early in labor because this technique appears to reduce total opioid requirements.
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Meperidine, a commonly used opioid, can be given in doses of 10-25 mg intravenously or 25-50 mg intramuscularly, usually up to a total of 100 mg. Maximal maternal and fetal respiratory depression is seen in 10-20 min following intravenous administration and in 1-3 h following intramuscular administration. Consequently, meperidine is usually administered early in labor when delivery is not expected for at least 4 h. Intravenous fentanyl, 25-100 mcg/h, has also been used for labor. Fentanyl in 25-100 mcg doses has a 3- to 10-min analgesic onset that initially lasts about 60 min, and lasts longer following multiple doses. However, maternal respiratory depression outlasts the analgesia. Lower doses of fentanyl may be associated with little or no neonatal respiratory depression and are reported to have no effect on Apgar scores. Morphine is not used because in equianalgesic doses it appears to cause greater respiratory depression in the fetus than meperidine and fentanyl. Agents with mixed agonist-antagonist activity (butorphanol, 1-2 mg, and nalbuphine, 10-20 mg intravenously or intramuscularly) are effective and are associated with little or no cumulative respiratory depression, but excessive sedation with repeat doses can be problematic.
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Promethazine (25-50 mg intramuscularly) and hydroxyzine (50-100 mg intramuscularly) can be useful alone or in combination with meperidine. Both drugs reduce anxiety, opioid requirements, and the incidence of nausea, but do not add appreciably to neonatal depression. A significant disadvantage of hydroxyzine is pain at the injection site following intramuscular administration. Nonsteroidal antiinflammatory agents, such as ketorolac, are not recommended because they suppress uterine contractions and promote closure of the fetal ductus arteriosus.
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Small doses (up to 2 mg) of midazolam (Versed) may be administered in combination with a small dose of fentanyl (up to 100 mcg) in healthy parturients at term to facilitate neuraxial blockade. At this dose, maternal amnesia has not been observed. Chronic administration of the longer-acting benzodiazepine diazepam (Valium) has been associated with fetal depression.
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Low-dose intravenous ketamine is a powerful analgesic. In doses of 10-15 mg intravenously, good analgesia can be obtained in 2-5 min without loss of consciousness. Unfortunately, fetal depression with low Apgar scores is associated with doses greater than 1 mg/kg. Large boluses of ketamine (>1 mg/kg) can be associated with hypertonic uterine contractions. Low-dose ketamine is most useful just prior to delivery or as an adjuvant to regional anesthesia. Some clinicians avoid use of ketamine because it may produce unpleasant psychotomimetic effects (see Chapter 9).
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In the past, reduced concentrations of volatile anesthetic agents (eg, methoxyflurane) in oxygen were sometimes used for relief of milder labor pain. Inhalation of nitrous oxide-oxygen remains in common use for relief of mild labor pain in many countries. As previously noted, nitrous oxide has minimal effects on uterine blood flow or uterine contractions.
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Regional Anesthetic Techniques
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Epidural or intrathecal techniques, alone or in combination, are currently the most popular methods of pain relief during labor and delivery. They can provide excellent analgesia while allowing the mother to be awake and cooperative during labor. Although spinal opioids or local anesthetics alone can provide satisfactory analgesia, techniques that combine the two have proved to be the most satisfactory in most parturients.

Moreover, the synergy between opioids and local anesthetics decreases dose requirements and provides excellent analgesia with few maternal side effects and little or no neonatal depression.
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Opioids may be given intrathecally as a single injection or intermittently via an epidural or intrathecal catheter (Table 41-2). Relatively large doses are required for analgesia during labor when epidural or intrathecal opioids are used alone. For example, the ED50 during labor is 124 mcg for epidural fentanyl and 21 mcg for epidural sufentanil. The higher doses may be associated with a high risk of side effects, most importantly respiratory depression. For that reason combinations of local anesthetics and opioids are most commonly used (see below). Pure opioid techniques are most useful for high-risk patients who may not tolerate the functional sympathectomy associated with spinal or epidural anesthesia (see Chapter 45). This group includes patients with hypovolemia or significant cardiovascular disease such as moderate to severe aortic stenosis, tetralogy of Fallot, Eisenmenger’s syndrome, or pulmonary hypertension. With the exception of meperidine, which has local anesthetic properties, spinal opioids alone do not produce motor blockade or sympathectomy. Thus, they do not impair the ability of the parturient to “push.” Disadvantages include less complete analgesia, lack of perineal relaxation, and side effects such as pruritus, nausea, vomiting, sedation, and respiratory depression. Side effects may be ameliorated with low doses of naloxone (0.1-0.2 mg/h intravenously).
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Intrathecal morphine in doses of 0.1-0.5 mg may produce satisfactory and prolonged (4-6 h) analgesia during the first stage of labor. Unfortunately, the onset of analgesia is slow (45-60 min), and these doses may not be sufficient in many patients. Higher doses are associated with a relatively high incidence of side effects. Morphine is therefore rarely used alone. The combination of morphine, 0.1-0.25 mg, and fentanyl, 12.5 mcg (or sufentanil, 5 mcg), may result in a more rapid onset of analgesia (5 min). Intermittent boluses of 10-15 mg of meperidine, 12.5-25 mcg of fentanyl, or 3-10 mcg of sufentanil via an intrathecal catheter can also provide satisfactory analgesia for labor. Early reports of fetal bradycardia following intrathecal opioid injections (eg, sufentanil) have not been confirmed by subsequent studies. Hypotension following administration of intrathecal opioids for labor is likely related to the resultant analgesia and decreased circulating catecholamine levels.
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Relatively large doses (≥7.5 mg) of epidural morphine are required for satisfactory labor analgesia, but doses larger than 5 mg are not recommended because of the increased risk of delayed respiratory depression and because the resultant analgesia is effective only in the early first stage of labor. Onset may take 30-60 min but analgesia lasts up to 12-24 h (as does the risk of delayed respiratory depression). Epidural meperidine, 50-100 mg, provides good, but relatively brief, analgesia (1-3 h). Epidural fentanyl, 50-150 mcg, or sufentanil, 10-20 mcg, usually produces analgesia within 5-10 min with few side effects, but it has a short duration (1-2 h). Although “single-shot” epidural opioids do not appear to cause significant neonatal depression, caution should be exercised following repeated administrations. Combinations of a lower dose of morphine, 2.5 mg, with fentanyl, 25-50 mcg (or sufentanil, 7.5-10 mcg), may result in a more rapid onset and prolongation of analgesia (4-5 h) with fewer side effects.
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Local Anesthetic/Local Anesthetic-Opioid Mixtures
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Epidural and spinal (intrathecal) analgesia more commonly utilizes local anesthetics either alone or with opioids for labor and delivery.

Analgesia during the first stage of labor requires neural blockade at the T10-L1 sensory level, whereas pain relief during the second stage of labor requires neural blockade at T10-S4.

Continuous lumbar epidural analgesia is the most versatile and most commonly-employed technique, because it can be used for pain relief for the first stage of labor as well as analgesia/anesthesia for subsequent vaginal delivery or cesarean section, if necessary. “Single-shot” epidural, spinal, or combined spinal epidural analgesia may be appropriate when pain relief is initiated just prior to vaginal delivery (the second stage). Obstetric caudal injections have largely been abandoned because of less versatility; although effective for perineal analgesia/anesthesia they require large volumes of local anesthetic to anesthetize upper lumbar and lower thoracic dermatomes. They have also been associated with early paralysis of the pelvic muscles that may interfere with normal rotation of the fetal head, and with a small risk of accidental puncture of the fetus.
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Absolute contraindications to regional anesthesia include patient refusal, infection over the injection site, coagulopathy, marked hypovolemia, and true allergies to local anesthetics. The patient’s inability to cooperate may prevent successful regional anesthesia. Neuraxial anesthesia and full anticoagulation is a dangerous combination. Regional anesthesia should generally not be performed within 6-8 h of a subcutaneous minidose of unfractionated heparin or within 12-24 h of administration of low-molecular-weight heparin (LMWH). Thrombocytopenia or concomitant administration of an antiplatelet agent increases the risk of spinal hematoma. A vaginal birth after cesarean (VBAC) delivery is not considered a contraindication to regional anesthesia during labor. Concern that the anesthesia may mask pain associated with uterine rupture during VBAC may not be justified, because dehiscence of a lower segment scar frequently does not cause pain even without epidural anesthesia; moreover, changes in uterine tone and contraction pattern may be more reliable signs.
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Before performing any regional block, appropriate equipment and supplies for resuscitation should be checked and made immediately available. Minimum supplies include oxygen, suction, a mask with a positive-pressure device for ventilation, a functioning laryngoscope and blades, endotracheal tubes (6 or 6.5 mm), oral and nasal airways, intravenous fluids, ephedrine, atropine, propofol, and succinylcholine. The ability to frequently monitor blood pressure and heart rate is mandatory. A pulse oximeter and capnograph should be readily available.
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Lumbar Epidural Analgesia
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Epidural analgesia for labor may be administered in early labor after the patient has been evaluated by her obstetrician.

When dilute mixtures of a local anesthetic and an opioid are used, epidural analgesia has little if any effect on the progress of labor. Concerns that regional analgesia will increase the likelihood of
oxytocin augmentation, operative (eg, forceps) delivery, or cesarean section, are unjustified. It is often advantageous to place an epidural catheter early, when the patient is less uncomfortable and can be positioned more easily. Moreover, should an urgent or emergent cesarean section become necessary, the presence of a well-functioning epidural catheter makes it possible to avoid general anesthesia.
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Parturients may be positioned on their sides or in the sitting position for the procedure. The sitting position often makes it easier to identify the midline and spine in obese patients. When epidural anesthesia is being given for vaginal delivery (second stage), the sitting position helps ensure good sacral spread.
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Because the lumbar epidural space pressure may be positive in some parturients, correct identification of the epidural space may be difficult. Unintentional dural puncture will occur even in experienced hands; the incidence of “wet taps” in obstetric patients is 0.25-9%, depending on clinician experience. Many practitioners add a compressible air bubble to the saline syringe and bounce the plunger to ensure that it moves freely and does not stick to the syringe wall (Figure 41-1A and C). Most clinicians advocate the midline approach, whereas a minority favors the paramedian approach. For the placement of a lumbar epidural catheter in the obstetric patient, most anesthesiologists advance the epidural needle with the left hand, which is braced against the patient’s back, while applying continuous pressure to a glass syringe filled with sterile saline (Figure 41-1A and C). Alternatively, some make use of the “wings” of the Weiss epidural needle by advancing it with both hands few millimeters at a time (Figure 41-1B). A change of tissue resistance is then tested continuously using tactile feedback when advancing the needle and by intermittently applying pressure to the air-filled loss-of resistance syringe. The later technique allows for precise control of needle advancement and may allow a better distinction of various tissue densities. If air is used for detecting loss of resistance, the amount injected should be limited; injection of larger volumes of air (>2-3 mL) in the epidural space has been associated with patchy or unilateral analgesia and headache. The average depth of the lumbar epidural space in obstetric patients is reported to be 5 cm from the skin. Placement of the epidural catheter at the L3-4 or L4-5 interspace is generally optimal for achieving a T10-S5 neural blockade. Ultrasound guidance has recently been offered as tool in assisting with the placement of an epidural catheter. This technique allows the practitioner to judge the depth of the epidural space and estimate the best angle of needle insertion. The potential benefit of this technique is most obvious in obese patients with poor anatomic landmarks. However, the technique is highly user-dependent, and few practitioners have adopted it.
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If unintentional dural puncture occurs, the anesthetist has two choices: (1) place the epidural catheter in the subarachnoid space for continuous spinal (intrathecal) analgesia and anesthesia (see below), or (2) remove the needle and attempt placement at a higher spinal level. The intrathecally-placed epidural catheter may be used as continuous spinal anesthetic, possibly reducing the incidence of post-dural puncture headache. If used in this fashion, an infusion of 0.0625-0.125% bupivacaine with fentanyl, 2-3 mcg/mL starting at 1-3 mL/h, is a reasonable choice.
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Choice of Epidural Catheter
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Many clinicians advocate use of a multiholed catheter instead of a single-holed catheter for obstetric anesthesia. Use of a multiholed catheter may be associated with fewer unilateral blocks and greatly reduces the incidence of false-negative aspiration when assessing for intravascular or intrathecal catheter placement. Advancing a multiholed catheter 4-6 cm into the epidural space appears to be optimal for obtaining adequate sensory levels. A single-hole catheter need only be advanced 3-5 cm into the epidural space. Shorter insertion depths (<5 cm), however, may favor dislodgment of the catheter out of the epidural space in obese patients following flexion/ extension movements of the spine. Spiral wire-reinforced catheters are very resistant to kinking. A spiral or spring tip, particularly when used without a stylet, is associated with fewer, less intense paresthesias and may also be associated with a lower incidence of accidental intravascular insertion.
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Choice of Local Anesthetic Solutions
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The addition of opioids to local anesthetic solutions for epidural anesthesia has dramatically changed the practice of obstetric anesthesia. The synergy between epidural opioids and local anesthetic solutions reflects separate sites of action, namely, opiate receptors and neuronal axons, respectively. When the two are combined, very low concentrations of both local anesthetic and opioid can be used. More importantly, the incidence of adverse side effects, such as hypotension and drug toxicity, is likely reduced. Although local anesthetics can be used alone, there is rarely a reason to do so. Moreover, when an opioid is omitted, the higher concentration of local anesthetic required (eg, bupivacaine, 0.25%, and ropivacaine, 0.2%) for adequate analgesia can impair the parturient’s ability to push effectively as labor progresses. Bupivacaine or ropivacaine in concentrations of 0.0625-0.125% with either fentanyl, 2-3 mcg/mL, or sufentanil, 0.3-0.5 mcg/mL, is most often used. In general, the lower the concentration of the local anesthetic the greater the concentration of opioid that is required. Very dilute local anesthetic mixtures (0.0625%) generally do not produce motor blockade and may allow some patients to ambulate (“walking” or “mobile” epidural). The long duration of action of bupivacaine makes it a popular agent for labor. Ropivacaine may be preferable because of its reduced potential for cardiotoxicity (see Chapter 16). At equi-analgesic doses, ropivacaine and bupivacaine appear to produce the same degree of motor block.
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The effect of epinephrine-containing solutions on the course of labor is somewhat controversial. Many clinicians use epinephrine-containing solutions only for intravascular test doses because of concern that the solutions may slow the progression of labor or adversely affect the fetus; others use only very dilute concentrations of epinephrine such as 1:800,000 or 1:400,000. Studies comparing these various agents have failed to find any differences in neonatal Apgar scores, acid-base status, or neurobehavioral evaluations.
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Epidural Activation for the First Stage of Labor
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Initial epidural injections may be done either before or after the catheter is placed. Administration through the needle can facilitate catheter placement, whereas administration through the catheter ensures proper function of the catheter. The following sequence is suggested for epidural activation:
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Test for unintentional subarachnoid or intravascular placement of the needle or catheter with a 3-mL test dose of a local anesthetic with 1:200,000 epinephrine (controversial; see the section on Prevention of Unintentional Intravascular and Intrathecal Injections). Many clinicians test with lidocaine 1.5% because of less toxicity following unintentional intravascular injection and a more rapid onset of spinal anesthesia than with bupivacaine and ropivacaine. The test dose should be injected between contractions to help reduce false positive signs of an intravascular injection (ie, tachycardia due to a painful contraction).
If after 5 min signs of intravascular or intrathecal injection are absent, with the patient supine and left uterine displacement, administer 10 mL of the local anesthetic-opioid mixture in 5-mL increments, waiting 1-2 min between doses, to achieve a T10-L1 sensory level. The initial bolus is usually composed of 0.1-0.2% ropivacaine or 0.0625-0.125% bupivacaine combined with either 50-100 mcg of fentanyl or 10-20 mcg of sufentanil.
Monitor with frequent blood pressure measurements for 20-30 min or until the patient is stable. Pulse oximetry should also be used. Oxygen is administered via face mask if there are any significant decreases in blood pressure or oxygen saturation readings.
Repeat steps 2 and 3 when pain recurs until the first stage of labor is completed. Alternatively, a continuous epidural infusion technique may be employed using bupivacaine or ropivacaine in concentrations of 0.0625-0.125% with either fentanyl, 1-5 mcg/mL, or sufentanil, 0.2-0.5 mcg/mL at a rate of 10 mL/h, which subsequently is adjusted to the patient’s analgesic requirements (range: 5-15 mL/h). A third choice would be to use patient-controlled epidural analgesia (PCEA). Some studies suggest that total drug requirements may be less and patient satisfaction is greater with PCEA compared with other epidural techniques. PCEA settings are typically a 5-mL bolus dose with a 5-10 min lockout and 0-12 mL/h basal rate; a 1-h limit of 15-25 mL may used. Migration of the epidural catheter into a blood vessel during a continuous infusion technique may be heralded by loss of effective analgesia; a high index of suspicion is required because overt signs of systemic toxicity may be absent. Erosion of the catheter through the dura results in a slowly progressive motor blockade of the lower extremities and a rising sensory level.
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Epidural Administration during the Second Stage of Labor
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Administration for the second stage of labor extends the block to include the S2-4 dermatomes. Whether a catheter is already in place or epidural anesthesia is just being initiated, the following steps should be undertaken:
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If the patient does not already have a catheter in place, identify the epidural space while the patient is in a sitting position. A patient who already has an epidural catheter in place should be placed in a semiupright or sitting position prior to injection.
Give a 3-mL test dose of local anesthetic (eg, lidocaine 1.5%) with 1:200,000 epinephrine. Again, the injection should be completed between contractions.
If after 5 min signs of an intravascular or intrathecal injection are absent, give 10-15 mL of additional local anesthetic-opioid mixture at a rate not faster than 5 mL every 1-2 min.
Administer oxygen by face mask, lay the patient supine with left uterine displacement, and monitor blood pressure every 1-2 min for the first 15 min, then every 5 min thereafter.
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Prevention of Unintentional Intravascular and Intrathecal Injections
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Safe administration of epidural anesthesia is critically dependent on avoiding unintentional intrathecal or intravascular injection.

Unintentional intravascular or intrathecal placement of an epidural needle or catheter is possible even when aspiration fails to yield blood or cerebrospinal fluid (CSF). The incidence of unintentional intravascular or intrathecal placement of an epidural catheter is 5-15% and 0.5-2.5%, respectively. Even a properly placed catheter can subsequently erode into an epidural vein or an intrathecal position. This possibility should be considered each time local anesthetic is injected through an epidural catheter.
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Test doses of lidocaine, 45-60 mg, bupivacaine, 7.5-10 mg, ropivacaine, 6-8 mg, or chloroprocaine, 100 mg, can be given to exclude unintentional intrathecal placement. Signs of sensory and motor blockade usually become apparent within 2-3 min and 3-5 min, respectively, if the injection is intrathecal.
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In patients not receiving β-adrenergic antagonists, the intravascular injection of a local anesthetic solution with 15-20 mcg of epinephrine consistently increases the heart rate by 20-30 beats/min within 30-60 s if the catheter (or epidural needle) is intravascular. This technique is not always reliable in parturients because they often have marked spontaneous baseline variations in heart rate with contractions. In fact, bradycardia has been reported in a parturient following intravenous injection of 15 mcg of epinephrine. Moreover, in animal studies, 15 mcg of epinephrine intravenously reduces uterine blood flow. Alternative methods of detecting unintentional intravascular catheter placement include eliciting tinnitus or perioral numbness following a 100-mg test dose of lidocaine or eliciting a chronotropic effect following injection of 5 mcg of isoproterenol. The use of dilute local anesthetic solutions and slow injection rates of no more than 5 mL at a time may also enhance detection of unintentional intravascular injections before catastrophic complications develop.
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Management of Complications
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Hypotension
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Generally defined as a greater than 20% decrease in the patient’s baseline blood pressure, or a systolic blood pressure less than 100 mm Hg, hypotension is a common side effect of neuraxial anesthesia. It is primarily due to decreased sympathetic tone and is greatly accentuated by aortocaval compression and an upright or semiupright position. Treatment should be aggressive in obstetric patients and consists of intravenous boluses of ephedrine (5-15 mg) or phenylephrine (25-50 mcg), supplemental oxygen, left uterine displacement, and an intravenous fluid bolus. Although the routine use of a crystalloid fluid bolus prior to dosing an epidural catheter is not effective in the prevention of hypotension, ensuring proper intravenous hydration of the pregnant patient is important. Use of the head-down (Trendelenburg) position is controversial because of its potentially detrimental effects on pulmonary gas exchange.
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Unintentional Intravascular Injection
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Early recognition of intravascular injection, facilitated by the use of small, repeated doses of local anesthetic instead of a large bolus, may prevent more serious local anesthetic toxicity, such as seizures or cardiovascular collapse. Intravascular injections of toxic doses of lidocaine or chloroprocaine usually present as seizures. Propofol, 20-50 mg, will terminate seizure activity. Maintenance of a patent airway and adequate oxygenation are critical; however, immediate endotracheal intubation with succinylcholine and cricoid pressure is rarely necessary. Intravascular injections of bupivacaine can cause rapid and profound cardiovascular collapse as well as seizure activity. Cardiac resuscitation may be exceedingly difficult and is aggravated by acidosis and hypoxia. An immediate infusion of 20% Intralipid has shown efficacy in reversing bupivacaine-induced cardiac toxicity. Amiodarone is the agent of choice for treating local anesthetic-induced ventricular arrhythmias.
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Unintentional Intrathecal Injection
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Even when dural puncture is recognized immediately after injection of local anesthetic, attempted aspiration of the local anesthetic will usually be unsuccessful. The patient should be placed supine with left uterine displacement. Head elevation accentuates the adverse cerebral effects of hypotension and should be avoided. Hypotension should be treated with phenylephrine and intravenous fluids. A high spinal level can also result in diaphragmatic paralysis, which necessitates intubation and ventilation with 100% oxygen. Delayed onset of a very high and often patchy or unilateral block may be due to unrecognized subdural injection (see Chapter 45), which is managed similarly.
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Postdural Puncture Headache (PDPH)
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Headache frequently follows unintentional dural puncture in parturients. A self-limited headache may occur without dural puncture; in such instances, injection of significant amounts of air into the epidural space during a loss-of-resistance technique may be responsible. PDPH is due to decreased intracranial pressure with compensatory cerebral vasodilation (see Chapter 45). Bed rest, hydration, oral analgesics, and caffeine sodium benzoate (500 mg added to 1000 mL intravenous fluids administered at 200 mL/h) may be effective in patients with mild headaches and as temporary treatment. Patients with moderate to severe headaches usually require an epidural blood patch (10-20 mL) (see Chapter 45). Prophylactic epidural blood patches are not recommended; 25-50% of patients may not require a blood patch following dural puncture. Delaying a blood patch for 24 h increases its efficacy. Intracranial subdural hematoma has been reported as a rare complication 1-6 weeks following unintentional dural puncture in obstetric patients.
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Maternal fever is often interpreted as chorioamnionitis and may trigger an invasive evaluation for neonatal sepsis. There is no evidence that epidural anesthesia affects maternal temperature or that neonatal sepsis is increased with epidural analgesia. An elevation in maternal temperature is associated with a high body mass index and with nulliparity in women and prolonged labor.
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Combined Spinal & Epidural (CSE) Analgesia
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Techniques using CSE analgesia and anesthesia may particularly benefit patients with severe pain early in labor and those who receive analgesia/anesthesia just prior to delivery. Intrathecal opioid and local anesthetic are injected after which an epidural catheter is left in place. The intrathecal drugs provide nearly immediate pain control and have minimal effects on the early progress of labor, whereas the epidural catheter provides a route for subsequent analgesia for labor and delivery or anesthesia for cesarean section. Addition of small doses of local anesthetic agents to intrathecal opioid injection greatly potentiates their analgesia and can significantly reduce opioid requirements. Thus, many clinicians will inject 2.5 mg of preservative-free
bupivacaine or 3-4 mg of
ropivacaine with intrathecal opioids for analgesia in the first stage of labor. Intrathecal doses for CSE are
fentanyl, 5-10 mcg, or
sufentanil, 5 mcg. Some studies suggest that CSE techniques may be associated with greater patient satisfaction and lower incidence of PDPH than epidural analgesia alone. A 24- to 27-gauge pencil-point spinal needle (Whitacre, Sprotte, or Gertie Marx) is used to minimize the incidence of PDPH.
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The spinal and epidural needles may be placed at separate interspaces, but most clinicians use a needle-through-needle technique at the same interspace. Use of saline for identification of the epidural space may potentially cause confusion of saline for CSF. With the needle-through-needle technique, the epidural needle is placed in the epidural space and a long spinal needle is then introduced through it and advanced farther into the subarachnoid space. A distinct pop is felt as the needle penetrates the dura. The needle-beside-needle technique typically employs a specially designed epidural needle that has a channel for the spinal needle. After the intrathecal injection and withdrawal of the spinal needle, the epidural catheter is threaded into position and the epidural needle is withdrawn. The risk of advancing the epidural catheter through the dural hole created by the spinal needle appears to be negligible when a 25-gauge or smaller needle is used. The epidural catheter, however, should be aspirated carefully and local anesthetic should always be given slowly and in small increments to avoid unintentional intrathecal injections. Moreover, epidural drugs should be titrated carefully because the dural hole may facilitate entry of epidural drugs into CSF and enhance their effects.
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Spinal anesthesia given just prior to delivery—also known as saddle block—provides profound anesthesia for operative vaginal delivery. Use of a 22-gauge or smaller, pencil-point spinal needle (Whitacre, Sprotte, or Gertie Marx) decreases the likelihood of PDPH. Hyperbaric tetracaine (3-4 mg), bupivacaine (2.5-5 mg), or lidocaine (20-40 mg) usually provides excellent perineal anesthesia. Addition of fentanyl (12.5-25 mcg) or sufentanil (5-7.5 mcg) significantly potentiates the block. A T10 sensory level can be obtained with slightly larger amounts of local anesthetic. Three minutes after injection, the patient is placed in the lithotomy position with left uterine displacement.