fluid bolus before 1000ccs, monitor BP (vasodilation), decreased O2 to baby. positioning: fetal position.
Epidural anesthesia or analgesia (block)
Relief from the pain of uterine contractions and birth (vaginal and cesarean) can be relieved by injecting a suitable local anesthetic agent (e.g., bupivacaine, ropivacaine), an opioid analgesic (e.g., fentanyl, sufentanil), or both into the epidural (peridural) space. Injection is made between the fourth and fifth lumbar vertebrae for a lumbar epidural block (see Figs. 10-8, B, and 10-10, A). Depending on the type, amount, and number of medications used, an anesthetic or analgesic effect will occur with varying degrees of motor impairment. The combination of an opioid with the local anesthetic agent reduces the dose of anesthetic required, thereby preserving a greater degree of motor function.
Epidural anesthesia and analgesia is the most effective pharmacologic pain-relief method for labor that is currently available. As a result, it is the most commonly used method for relieving pain during labor in the United States and its use has been increasing. Nearly two thirds of American women giving birth choose epidural analgesia (AAP & ACOG, 2007; Bucklin et al., 2005; Hawkins et al., 2007). For relieving the discomfort of labor and vaginal birth, a block from T10 to S5 is required. For cesarean birth, a block from at least T8 to S1 is essential. The diffusion of epidural anesthesia depends on the location of the catheter tip, the dose and volume of the anesthetic agent used, and the woman's position (e.g., horizontal or head-up position). The woman must cooperate and maintain her position without moving during insertion of the epidural catheter so as to prevent misplacement, neurologic injury, or hematoma formation (Cunningham et al., 2005).
Epidural anesthesia effectively relieves the pain caused by uterine contractions. For most women, however, it does not completely remove the pressure sensations that occur as the fetus descends in the pelvis.
For the induction of an epidural block, the woman is positioned as for a spinal block. She may sit with her back curved or she may assume a modified Sims position with her shoulders parallel, legs slightly flexed, and back arched (see Fig. 10-11). A large-bore needle is inserted into the epidural space. A catheter is then threaded through the needle until its tip rests in the epidural space. Then the needle is removed and the catheter is taped in place. After the epidural catheter is inserted, a small amount of medication, called a test dose, is injected to be sure that the catheter has not been accidentally placed in the subarachnoid (spinal) space or in a blood vessel (Hawkins et al., 2007).
After the epidural has been initiated the woman is positioned preferably on her side so that the uterus does not compress the ascending vena cava and descending aorta, which can impair venous return, reduce cardiac output and blood pressure, and decrease placental perfusion. Her position should be alternated from side to side every hour. Upright positions and ambulation may be possible, depending on the degree of motor impairment. Oxygen should be available if hypotension occurs despite maintenance of hydration with IV fluid and displacement of the uterus to the side. Ephedrine or phenylephrine (vasopressors used to increase maternal blood pressure) and increased IV fluid infusion may be needed (see Emergency box). The FHR, contraction pattern, and progress in labor must be monitored carefully because the woman may not be aware of changes in the strength of the uterine contractions or the descent of the presenting part.
Several methods can be used for an epidural block. An intermittent block is achieved by using repeated injections of anesthetic solution; it is the least common method. The most common method is the continuous block, achieved by using a pump to infuse the anesthetic solution through an indwelling plastic catheter. Patient-controlled epidural analgesia (PCEA) is the newest method; it uses an indwelling catheter and a programmed pump that allows the woman to control the dosing. This method has been found to provide optimal analgesia with better maternal satisfaction during labor while decreasing the amount of local anesthetic used (Saito et al., 2005).
The advantages of an epidural block are numerous: The woman remains alert and is more comfortable and able to participate, good relaxation is achieved, airway reflexes remain intact, only partial motor paralysis develops, gastric emptying is not delayed, and blood loss is not excessive. Fetal complications are rare but may occur in the event of rapid absorption of the medication or marked maternal hypotension. The dose, volume, type, and number of medications used can be modified to allow the woman to push and to assume upright positions and even to walk, to produce perineal anesthesia, and to permit forceps-assisted, vacuum-assisted, or cesarean birth if required (Cunningham et al., 2005).
The disadvantages of epidural block also are numerous. The woman's ability to move freely and to maintain control of her labor is limited, related to the use of numerous medical interventions (e.g., an IV infusion and electronic monitoring) and the occurrence of orthostatic hypotension and dizziness, sedation, and weakness of the legs. CNS effects (Box 10-4) can occur if a solution containing a local anesthetic agent is accidentally injected into a blood vessel or if excessive amounts of local anesthetic are given. High spinal or "total spinal" anesthesia, resulting in respiratory arrest, can occur if the relatively high dose of local anesthetic used with an epidural block is accidentally injected into the subarachnoid space. Women who receive an epidural have a higher rate of fever (i.e., intrapartum temperature of 38° C or higher), especially when labor lasts longer that 12 hours; the temperature elevation most likely is related to thermoregulatory changes, although infection cannot be ruled out. The elevation in temperature can result in fetal tachycardia and neonatal workup for sepsis, whether or not signs of infection are present (see Box 10-4).
Severe hypotension (more than a 20% decrease in baseline blood pressure) as a result of sympathetic blockade can be an outcome of an epidural block (Anim-Somuah, Smyth, & Howell, 2005) (see Emergency box). It can result in a significant decrease in uteroplacental perfusion and oxygen delivery to the fetus. Urinary retention and stress incontinence can occur in the immediate postpartum period. Pruritus (itching) is a side effect that often occurs with the use of an opioid, especially fentanyl. A relationship between epidural analgesia and longer second-stage labor, use of oxytocin, and forceps-assisted or vacuum-assisted birth has been documented. Research findings have been unable to demonstrate a significant increase in cesarean birth associated with epidural analgesia (Anim-Somuah et al.). For some women, the epidural block is not effective, and a second form of analgesia is required to establish effective pain relief. When women progress rapidly in labor, pain relief may not be obtained before birth occurs.
BOX 10-4 Side Effects of Epidural and Spinal Anesthesia
• Local anesthetic toxicity
• Tinnitus (ringing in the ears)
• Metallic taste
• Numbness of the tongue and mouth
• Bizarre behavior
• Slurred speech
• Loss of consciousness
• High or total spinal anesthesia
• Urinary retention
• Pruritus (itching)
• Limited movement
• Longer second stage labor
• Increased use of oxytocin
• Increased likelihood of forceps- or vacuum-assisted birth
Combined spinal-epidural analgesia
In the combined spinal-epidural (CSE) analgesia technique, sometimes called a "walking epidural," an epidural needle is inserted into the epidural space. Before the epidural catheter is placed, a smaller-gauge spinal needle is inserted through the bore of the epidural needle into the subarachnoid space. A small amount of opioid or combination of opioid and local anesthetic is then injected intrathecally to provide analgesia rapidly. Afterward the epidural catheter is inserted as usual. The CSE technique is an increasingly popular approach that can be used to block pain transmission without compromising motor ability. The concentration of opioid receptors is high along the pain pathway in the spinal cord, in the brainstem, and in the thalamus. Because these receptors are highly sensitive to opioids, a small quantity of an opioid-agonist analgesic produces marked pain relief lasting for several hours. If additional pain relief is needed, medication can be injected through the epidural catheter (see Fig. 10-10, A). The most common side effects of CSE are pruritus and nausea (Hawkins et al., 2007). CSE analgesia may also be associated with fetal bradycardia, necessitating close assessment of fetal heart rate (Cunningham et al., 2005).
Although women can walk, they often choose not to do so because of sedation and fatigue, abnormal sensations perceived in their legs, weakness of the legs, and a feeling of insecurity. Health care providers are often reluctant to encourage or assist women to ambulate for fear of injury. However, women can be assisted to change positions and use upright positions during labor and birth. Upright positioning is associated with less pain, more efficient labor progress, and a lower incidence of forceps- or vacuum-assisted birth (Albers, 2007; Berghella et al., 2008). Laboring upright also conveys a sense of normalcy, autonomy, and personal control (Albers).
Epidural and intrathecal (spinal) opioids
Opioids also can be used alone, eliminating the effect of a local anesthetic altogether. The use of epidural or intrathecal opioids without the addition of a local anesthetic agent during labor has several advantages. Opioids administered in this manner do not cause maternal hypotension or affect vital signs. The woman feels contractions but not pain. Her ability to bear down during the second stage of labor is preserved because the pushing reflex is not lost, and her motor power remains intact.
Fentanyl, sufentanil, or preservative-free morphine may be used. Fentanyl and sufentanil produce short-acting analgesia (i.e., 1.5 to 3.5 hours), and morphine may provide pain relief for 4 to 7 hours. Morphine may be combined with fentanyl or sufentanil. Using short-acting opioids with multiparous women and morphine with nulliparous women or women with a history of long labor would be appropriate. For most women, intrathecal opioids do not provide adequate analgesia for second-stage labor pain, episiotomy, or birth (Cunningham et al., 2005). Pudendal nerve blocks or local perineal infiltration anesthesia may be necessary.
A more common indication for the administration of epidural or intrathecal analgesics is the relief of postoperative pain. For example, women who give birth by cesarean can receive fentanyl or morphine through a catheter. The catheter may then be removed, and the women are usually free of pain for 24 hours. The catheter is occasionally left in place in the epidural space in case another dose is needed.
Women receiving epidurally administered morphine after a cesarean birth may ambulate sooner than women who do not. The early ambulation and freedom from pain also facilitate bladder emptying, enhance peristalsis, and prevent clot formation in the lower extremities (e.g., thrombophlebitis). Women may require additional medication for pain during the first 24 hours after surgery. If so, they will usually be given oral analgesics (e.g., oxycodone/acetaminophen [Percocet]), rather than IV or IM narcotics.
Side effects of opioids administered by the epidural and intrathecal routes include nausea, vomiting, pruritus, urinary retention, and delayed respiratory depression. These side effects are more common when morphine is administered. Antiemetics, antipruritics, and opioid antagonists are used to relieve these symptoms. For example, naloxone (Narcan), nalbuphine (Nubain), or metoclopramide (Reglan) may be administered. Hospital protocols or detailed physician orders should provide specific instructions for the treatment of these side effects. Use of epidural opioids is not without risk. Respiratory depression is a serious concern; for this reason the woman's respiratory rate should be assessed and documented every hour for 24 hours, or as designated by hospital protocol. Naloxone should be readily available for use if the respiratory rate decreases to less than 10 breaths per minute or if the oxygen saturation rate decreases to less than 89%. Administration of oxygen by facemask also may be initiated, and the anesthesia care provider should be notified.
Contraindications to epidural blocks
Some contraindications to epidural analgesia include the following (Cunningham et al., 2005; Hawkins et al., 2007):
• Active or anticipated serious maternal hemorrhage (Acute hypovolemia leads to increased sympathetic tone to maintain the blood pressure. Any anesthetic technique that blocks the sympathetic fibers can produce significant hypotension that can endanger the mother and baby.)
• Coagulopathy (If a woman is receiving anticoagulant therapy or has a bleeding disorder, injury to a blood vessel may cause the formation of a hematoma that may compress the cauda equina or the spinal cord and lead to serious CNS complications.)
• Infection at the injection site (Infection can be spread through the peridural or subarachnoid spaces if the needle traverses an infected area.)
• Increased intracranial pressure caused by a mass lesion.
• Maternal refusal.
• Some types of maternal cardiac conditions.
Epidural block effects on the neonate
Analgesia or anesthesia during labor and birth has little or no lasting effect on the physiologic status of the neonate. Currently, no evidence has been found that the administration of analgesia or anesthesia during labor and birth has a significant effect on the child's later mental and neurologic development (AAP & ACOG, 2007).