Labor and Delivery
Leonard Allmond
Brenda A. Bucklin
Joy L. Hawkins
CASE SUMMARY
A 27-year-old woman presents to the emergency room with a persistent headache of 24 hours duration. Five days ago, she underwent combined spinal epidural (CSE) labor analgesia for an uncomplicated vaginal delivery. Following evaluation, emergency room physicians make a diagnosis of postdural puncture headache (PDPH). Five hundred milligrams of caffeine are administered intravenously without improvement of symptoms. The obstetric anesthesia service is called to evaluate the patient for placement of an epidural blood patch (EBP). Evaluation reveals a nonpositional headache without diplopia, tinnitus, or relieving factors. The patient is also complaining of epigastric pain. Before caffeine administration, the patient’s blood pressure was 160/110. The obstetric anesthesiologist suggests obtaining a urine sample for evaluation of urine protein. In addition, an obstetric consult is recommended to evaluate the patient for possible postpartum preeclampsia. The urine dipstick reveals 3+ proteinuria, and the patient is admitted for treatment of postpartum preeclampsia. On her way to the ward, she has an eclamptic seizure.
What Are the Complications Associated with Analgesia for Labor?
Many parturients choose neuraxial analgesia to alleviate pain associated with labor and delivery. More than 50% of women in the United States receive either an epidural or CSE analgesia during labor.1 The popularity of these neuraxial techniques has increased because they are the most effective forms of providing analgesia for labor. Although the techniques to perform and administer this form of analgesia are generally safe for mother and fetus, there are several associated complications with which consulting anesthesiologists should familiarize themselves. The parturient should be well informed of the associated risks including failure of analgesia, noninfectious maternal fever, neurologic injury, hypotension, alteration of progress of labor, and PDPH.
▪ FAILURE OF ANALGESIA
One of the most important and common complications of neuraxial techniques is failure of or inadequate analgesia. The overall failure rate of epidural catheters used during labor has been reported to be as high as 12%.2 The term, failure, itself is quite broad and includes elements such as failure to produce an adequate block, need for catheter replacement, catheter migration/dislodgment, and inability to insert a catheter despite cannulation of the epidural space. By making an attempt to identify the etiology of failure, it may be possible to improve the effectiveness of a neuraxial blockade.
Mechanisms of Failed Analgesia
Midline Structures
Several factors may contribute to epidural block failure. The presence of epidural midline structures may be responsible for some failed blocks. Autopsy, imaging, and endoscopy have confirmed the existence of the plica mediana dorsalis, a midline band in the epidural space. This band may cause a deflection of the Touhy needle to one side of the epidural space, uneven spread of local anesthetic, or unilateral block. The variability in spinal nerve root diameter also may play a role in some block failures. Larger spinal nerve roots such as sacral roots have longer diffusion distances for local anesthetics, which could result in incomplete blockade of those nerves. Failure of sacral nerve root blockade can occur up to 17% of the time. A body
mass index >30 and extremes of stature have been associated with higher failure rates and greater probability of pain, respectively; however, it is unclear how these variations in body habitus contribute to epidural failure.3
mass index >30 and extremes of stature have been associated with higher failure rates and greater probability of pain, respectively; however, it is unclear how these variations in body habitus contribute to epidural failure.3
Catheter Position and Defects
Several factors related to methodology and equipment should be considered as well. Initial catheter misplacement can occur. In a study identifying failed catheter placement using epidurograms, three types of malpositions were revealed, including transforaminal escape, passage to the anterior epidural space, and paravertebral location. Catheter migration or dislodgment results in the local anesthetic not being delivered to the epidural space. Catheter defects such as reduced patency of the ports and aberrant placement of the distal hole in the catheter also have been reported in failed epidural blocks. The number of catheter ports (uniport vs. multiport) has been found to affect block failure rates, with single-orifice and multi-orifice catheters having a 14.3% and 9.3% failure rate, respectively. Other evidence has, however, suggested no difference in the block failure rate between the two catheter types.3
Catheter Placement Techniques
The preferences of those placing the epidural catheters can also affect the incidence of catheter failure. A randomized study in parturients found that use of air for loss of resistance resulted in a higher incidence of inadequate analgesia compared with using saline.4 In addition, the volume of local anesthetic injected into the epidural space may be important for block success. Using the same milligram amount of the drug, a higher volume has been found to provide better analgesia compared to a smaller volume.
The distance of catheter insertion also influences the incidence of failed block. The optimal distance of catheter insertion into the epidural space is probably in the range of 2 to 6 cm, although 5 cm is the distance that many clinicians use to reduce the risk of dislodgment, provide adequate analgesia, and reduce the risk of intravascular cannulation.
Lastly, the technical skill and experience of the anesthesiologist, which integrates some of the aforementioned factors, may greatly contribute to the success of the block. Indeed, failure of blockade varies inversely with experience.3
Is a Combined Spinal Epidural Better Than Epidural Analgesia?
One factor that may be overlooked when considering the etiology of neuraxial failure is the choice of either epidural or CSE for labor analgesia. There is a growing body of evidence suggesting that CSE provides more effective analgesia. In addition, CSE is faster in onset5 and has a lower failure and “wet tap” rate.6,7 In a series of more than 19,000 patients, the failure rate for CSE was found to be 10% compared with 14% when epidural catheters are used alone.2 Despite these results, there are several theoretic disadvantages to CSE, including the following:
Unproven epidural catheter effectiveness
The risk of threading the epidural catheter intrathecally
Excessively high blocks
Increased risk of PDPH
Increased risk of fetal bradycardia from spinal opioids
Maternal respiratory depression
The risk of introduction of metal into the subarachnoid space
Increased equipment costs
Nonetheless, these potential disadvantages and/or complications do not occur at a greater rate than with epidural catheters alone.5 In addition, one study found that CSE did not result in lower catheter failure rates;8 however, these investigators did not administer a subarachnoid drug after dural puncture. Although the potential etiologies for failure of neuraxial analgesia (including choice of technique) are many, it is important to effectively manage a failed block to maximize patient safety and satisfaction.
What Is the Approach for the Patient with Failed Labor Analgesia?
▪ HISTORY AND PHYSICAL EXAMINATION
Failures of both CSE and epidural catheters are evaluated similarly. Soliciting a detailed history of the nature of the pain is the first step. Questions that focus on the location (e.g., unilateral, perineal, abdominal), temporal association, and intensity may help further elucidate the etiology. The physical examination should focus on the bilateral levels of sensory and motor blockade in the lower extremities. It is important to rule out symptoms of femoral, obturator, and sciatic neuropathies as potential etiologies of motor blockade. The history and physical examination will usually guide the anesthesiologist toward the proper treatment, even if the etiology remains unclear. Ultimately, the specific etiology of the pain may never be discovered, but more importantly, adequate analgesia should be achieved.
▪ TREATMENT
Volume of Anesthetic
One of the most common maneuvers employed in the treatment of inadequate labor analgesia is to bolus
the epidural catheter with a local anesthetic and/or opioid (see Fig. 47.1). This is most appropriate when the level of sensory blockade is bilateral but of limited extension, or when the progress of labor has changed so significantly that it triggers an increase in pain intensity. In these cases, there are many potential choices for treatment including type, volume, and concentration of local anesthetic. A higher volume may be more effective than a lower volume in maximizing dermatomal spread because volume is a major determinant of block height in epidural analgesia and anesthesia.9 Lidocaine, bupivacaine, or ropivacaine can be administered as a bolus, but bupivacaine may be a superior choice because of its longer duration and minimal effects on motor blockade. Ropivacaine has similar properties to bupivacaine, except it is less potent and more expensive. Lidocaine, on the other hand, is extremely effective in alleviating pain, but can produce motor blockade. Another disadvantage is that after a lidocaine bolus, it may be impossible to achieve analgesia with a more dilute solution if the patient develops further breakthrough pain. Given the short duration of lidocaine, this is a common scenario with its use. Overall, 10 to 20 mL of dilute bupivacaine may be the best choice when a bolus dose is administered for breakthrough pain. It is important to administer incremental doses of local anesthetics, regardless of the solution chosen, to avoid total spinal anesthesia or local anesthetic toxicity.
the epidural catheter with a local anesthetic and/or opioid (see Fig. 47.1). This is most appropriate when the level of sensory blockade is bilateral but of limited extension, or when the progress of labor has changed so significantly that it triggers an increase in pain intensity. In these cases, there are many potential choices for treatment including type, volume, and concentration of local anesthetic. A higher volume may be more effective than a lower volume in maximizing dermatomal spread because volume is a major determinant of block height in epidural analgesia and anesthesia.9 Lidocaine, bupivacaine, or ropivacaine can be administered as a bolus, but bupivacaine may be a superior choice because of its longer duration and minimal effects on motor blockade. Ropivacaine has similar properties to bupivacaine, except it is less potent and more expensive. Lidocaine, on the other hand, is extremely effective in alleviating pain, but can produce motor blockade. Another disadvantage is that after a lidocaine bolus, it may be impossible to achieve analgesia with a more dilute solution if the patient develops further breakthrough pain. Given the short duration of lidocaine, this is a common scenario with its use. Overall, 10 to 20 mL of dilute bupivacaine may be the best choice when a bolus dose is administered for breakthrough pain. It is important to administer incremental doses of local anesthetics, regardless of the solution chosen, to avoid total spinal anesthesia or local anesthetic toxicity.
 FIGURE 47.1 Suggested algorithm for troubleshooting epidural catheters. IV, intravenous; PCA, patient-controlled analgesia. |
Bolus Dosages
It is not uncommon for the initial bolus of local anesthetic to be inadequate in producing satisfactory analgesia, even in the presence of a functional epidural catheter. One particular scenario is when the parturient has effective analgesia after an initial bolus, but it is short-lived. Pain may only be relieved by repeat boluses; in this case, it may be effective to increase the concentration or rate of the continuous epidural infusion. The need for a repeat bolus at frequent intervals serves as an indicator for higher doses of local anesthetic to match the intensity of pain at a particular point in labor. This goal can be achieved by either an increase in rate or concentration of the infusion; however, the risk associated with higher concentrations is a potential increase in motor blockade or the development of systemic toxicity.
Patient-Controlled Analgesia
Another option is the use of patient-controlled epidural analgesia (PCEA), if available. Major advantages include decreased local anesthetic use, and increased patient satisfaction. In addition, because the patient can self-administer a bolus of the drug to the point of comfort, the workload for the anesthesiologist is reduced.5
Catheter Replacement
The parturient may also experience inadequate pain relief after one or more boluses. In these cases, early catheter replacement should be considered because any patient in labor is considered at risk for cesarean delivery.2 As discussed earlier, it may be impossible to achieve adequate analgesia with a particular catheter. If a catheter is ineffective during labor, there is an increased chance that anesthesia will be inadequate for the cesarean section.9 Early catheter replacement usually results in effective analgesia.
The rate of multiple epidural catheter replacements has been reported to be approximately 1.9% with a standard epidural technique and <1% when a CSE is performed.2 Catheter replacement may very well be the least time-consuming maneuver to achieve adequate analgesia and is likely to maximize overall patient satisfaction with anesthetic care.
Intravenous Analgesia
Unfortunately, although rare, there are cases in which adequate analgesia cannot be achieved with epidural blockade despite the maneuvers discussed. In these situations, it may be necessary to supplement inadequate blockade with, or completely convert to, intravenous (IV) analgesia. IV agents such as opioids or ketamine are effective for labor analgesia; however, they have significant side effects when compared to neuraxial blockade, including respiratory depression and excessive sedation in both
the mother and neonate. Opioids are most effective when administered by patient-controlled analgesia (PCA). Fentanyl is a good choice for PCA administration because of its rapid onset and short duration. The use of PCA also leads to greater patient satisfaction and lower overall opioid consumption when compared to intermittent bolus dosing by nurses.10 Ketamine also can be added to the PCA to reduce fentanyl use or as an excellent alternative for short-term analgesia (usually during late stage 2 of labor). When administered by intermittent bolus, doses of 10 mg up to 1 mg per kg produce intense analgesia with minimal respiratory depression. Doses >1 mg per kg may result in oversedation or unconsciousness with loss of airway reflexes. This is an undesirable situation, especially in the obstetric population.
the mother and neonate. Opioids are most effective when administered by patient-controlled analgesia (PCA). Fentanyl is a good choice for PCA administration because of its rapid onset and short duration. The use of PCA also leads to greater patient satisfaction and lower overall opioid consumption when compared to intermittent bolus dosing by nurses.10 Ketamine also can be added to the PCA to reduce fentanyl use or as an excellent alternative for short-term analgesia (usually during late stage 2 of labor). When administered by intermittent bolus, doses of 10 mg up to 1 mg per kg produce intense analgesia with minimal respiratory depression. Doses >1 mg per kg may result in oversedation or unconsciousness with loss of airway reflexes. This is an undesirable situation, especially in the obstetric population.
Inadequate analgesia is, unfortunately, a common scenario for labor and delivery, and there are numerous potential etiologies. Regardless of the cause, troubleshooting should be promptly performed to ensure patient satisfaction and safety. Catheter replacement should be considered early because all parturients are at risk for cesarean delivery. Fentanyl PCA and IV ketamine should be considered options of last resort when effective neuraxial analgesia cannot be achieved.
What Are the Effects of Labor Analgesia on the Progress and Outcome of Labor?
The influence of epidural analgesia on the progress and outcome of labor and delivery has been one of the most controversial areas of obstetric anesthesia. Many studies have evaluated the effects of epidural analgesia on the progress of labor and rates of cesarean and instrumental deliveries, as well as fetal and neonatal outcome. Limitations in the design of many studies—including small sample size, lack of randomization and retrospective analysis—have led to erroneous interpretations and conclusions with respect to the effects of epidural analgesia on labor and outcome of delivery.11
A series of retrospective studies from 1989 to 1996 first suggested that epidural analgesia was associated with increased rates of cesarean delivery secondary to dystocia.11 These studies demonstrated up to a sixfold increase in rates of cesarean delivery in parturients receiving epidural analgesia compared with those receiving systemic opioids or no analgesia. This group of studies suffered from several design flaws that make it difficult to draw any definitive conclusions. First, there are inherent biases attributed to retrospective study designs. Most importantly, the two groups being compared may not have shared equivalent risks, which was the case in several studies. In most retrospective studies, women receiving epidural analgesia more often had induced labor, were frequently nulliparous, and had a smaller pelvis with larger babies.
One group of population-based studies that were inherently less biased demonstrated no difference in cesarean rates between parturients who received epidural analgesia and those who did not.11 These studies arose from a policy change in the Department of Defense, which ruled that all military hospitals providing obstetric care must make epidural analgesia available to all patients in labor who request it. In military hospitals, before 1993, very few women received epidural analgesia for labor. Shortly thereafter, most parturients elected to have epidural analgesia. This type of study design should ensure that at least the characteristics of the patient population are similar. Because these studies were not controlled for changes in the practice style (e.g., increased instrumental deliveries by obstetricians because patients had good analgesia) that may have incited increased epidural administration, these studies were flawed, thereby limiting their capacity in drawing definitive conclusions.
Fortunately, included in the aforementioned studies was a series of randomized, controlled trials conducted to analyze the question of whether the administration of epidural analgesia for labor increases the rate of cesarean delivery.11 Randomized, controlled trials (preferably double-blinded) serve as the gold standard for answering these types of clinical research questions. However, blinding in these studies is impossible, considering that epidural analgesia clearly is superior when compared with systemic opioids or no analgesia. Of more than 12 clinical trials, only 1 has shown an increased rate of cesarean delivery with epidural administration.12 That study has been criticized for being underpowered to make its primary conclusion from the data. The study was terminated early for an unacceptably high cesarean rate in the epidural group, and one more cesarean delivery in the control group would have eliminated statistical significance. The other trials and meta-analyses of these trials have shown that epidural analgesia does not increase cesarean delivery rates.10,13
A recent study by Wong et al. further substantiated the conclusion that epidural analgesia does not increase rates of cesarean delivery.14 In this randomized controlled trial, two groups were compared. In the first group, parturients received intrathecal fentanyl at their first request for analgesia if cervical dilation was <4 cm. At the second request for analgesia, the women were administered epidural analgesia with bupivacaine. In the second group, IV hydromorphone was administered at first request if cervical dilation was <4 cm. Epidural analgesia was then administered when the cervical dilation was >4 cm or at the third request for analgesia. No significant differences were found in rates of cesarean delivery between the two groups. Collectively, these randomized controlled trials strongly suggest that epidural analgesia does not increase the cesarean delivery rate compared to systemic opioid analgesia.
▪ LENGTH OF LABOR
The study by Wong et al. also demonstrates important secondary outcome results (e.g., duration of labor).14 The median time from initiation of analgesia to complete dilation and to vaginal delivery was significantly reduced in
the early epidural group compared with the late epidural group (90 and 80 minutes, respectively). It should be noted that the women in the systemic analgesia group had lesser degrees of cervical dilation at first request for analgesia, thereby explaining some of the differences in time to complete dilation and vaginal delivery. Before this study, most agreed that epidural analgesia prolonged both stage 1 and 2 of labor by approximately 20 to 50 minutes and 15 to 30 minutes, respectively.11 This was observed in both randomized trials and meta-analyses. However, these studies were significantly affected by high patient crossover rates from systemic analgesia to epidural analgesia. Intention-to-treat analysis still has demonstrated a significant difference. Overall, the data suggests that epidural analgesia prolongs stage 1 and 2 of labor, but further study may be necessary to determine whether this increase in length of labor is clinically relevant. Since there is no evidence that links early epidural placement to adverse outcomes, the American Society of Anesthesiologists and the American College of Obstetricians and Gynecologists issued a joint statement declaring that a woman’s request for pain relief at any time during labor is sufficient indication to provide such relief.15
the early epidural group compared with the late epidural group (90 and 80 minutes, respectively). It should be noted that the women in the systemic analgesia group had lesser degrees of cervical dilation at first request for analgesia, thereby explaining some of the differences in time to complete dilation and vaginal delivery. Before this study, most agreed that epidural analgesia prolonged both stage 1 and 2 of labor by approximately 20 to 50 minutes and 15 to 30 minutes, respectively.11 This was observed in both randomized trials and meta-analyses. However, these studies were significantly affected by high patient crossover rates from systemic analgesia to epidural analgesia. Intention-to-treat analysis still has demonstrated a significant difference. Overall, the data suggests that epidural analgesia prolongs stage 1 and 2 of labor, but further study may be necessary to determine whether this increase in length of labor is clinically relevant. Since there is no evidence that links early epidural placement to adverse outcomes, the American Society of Anesthesiologists and the American College of Obstetricians and Gynecologists issued a joint statement declaring that a woman’s request for pain relief at any time during labor is sufficient indication to provide such relief.15
▪ OTHER CONCERNS
In addition to rates of cesarean delivery and length of labor, there are other concerns regarding the effects of epidural analgesia for labor. Given that parturients with epidurals tend to have longer labors, there has been an increase in oxytocin use and rate of operative vaginal delivery.16 However, it is unclear whether obstetricians are more comfortable with inducing labor or performing operative vaginal deliveries in the setting of excellent pain relief. The increase in operative vaginal delivery, particularly forceps delivery, has resulted in a higher rate of perineal injury, leading to fecal incontinence in those women who receive epidural analgesia for labor.16 There has also been speculation that epidural analgesia results in more fetal head malposition.17,18 Current evidence regarding fetal malposition has been controversial, with some studies showing an increased rate of occiput posterior presentation, whereas others have not.
▪ EFFECTS ON FETUS AND NEONATAL OUTCOME
Neonate
Considering that some evidence shows that epidural analgesia affects the length of labor and use of operative vaginal delivery, one could assume epidural analgesia also affects neonatal outcome. Several studies have attempted to characterize the effects of epidural analgesia on the neonate with measurements, such as umbilical cord blood gases and Apgar scores.16 To date, no adverse effects of regional anesthesia have been found. One meta-analysis of five randomized, controlled trials found that neonates born of mothers who had epidural analgesia had increased fetal base excess compared to those of mothers who received systemic opioids.19 These results are not surprising, given that systemic opioids readily cross the placenta to a greater degree than epidural medications. Another finding determined that fetal base excess at birth was improved when epidural analgesia was administered during labor.19
Fetus
An additional area of concern has been the effect of epidural analgesia on fetal heart tones (FHT). There is a theoretic risk of fetal bradycardia in the setting of epidural analgesia, secondary to hypotension induced by sympathetic blockade. One study comparing the effects of epidural analgesia on FHT to IV meperidine demonstrated no evidence of adverse effects.20 However, CSE techniques have produced different results with regard to FHTs. The use of CSE has been shown to increase the rate of emergency cesarean delivery for fetal bradycardia in several studies, especially when intrathecal opioids are administered;21 on the other hand, other studies have found no such relation.22,23 Collectively, the evidence to date suggests that epidural analgesia and CSE have minimal effects on fetal and neonatal outcome.
Most of the controversy surrounding the effects of epidural analgesia on the progress of labor has abated. Current evidence suggests that epidural analgesia for labor does not result in higher rates of cesarean delivery. The length of labor is likely prolonged by epidural analgesia, but the clinical significance of this increase is unclear. Operative vaginal delivery, perineal injury, and oxytocin use occur at increased rates when parturients receive epidural analgesia. Despite these concerns, there is no evidence in the literature to suggest that adverse fetal or neonatal effects result from epidural analgesia administered to the laboring mother.
What Are the Neurologic Complications Associated with Neuraxial Labor Analgesia?
INCIDENCE
Although rare, both parturients and anesthesiologists fear neurologic complications as a result of neuraxial labor analgesia and anesthesia. Overall estimates for the incidence of neurologic injury vary widely, from 1 per 10,000 to 1 per 500,000.24 However, the true incidence is difficult to quantify because injuries are rare, and estimates cannot be obtained from randomized, controlled trials in a practicable manner. Periodically, retrospective and prospective studies are published that have analyzed the risk factors associated with neurologic injury in the setting of neuraxial analgesia and anesthesia. A recent retrospective study from Sweden, in which approximately 255,000
neuraxial blocks were administered over a 10-year period, determined that the incidence of injury in parturients was approximately 1 per 25,000 for epidural blockade.25 More neurologic complications occurred with epidural than with spinal anesthesia. Additionally, more complications were found in surgical blocks than obstetric blocks. These injuries included spinal hematoma, epidural abscess, spinal cord lesions, subdural hematoma, permanent abducens paralysis, and Horner’s syndrome with facial pain.
neuraxial blocks were administered over a 10-year period, determined that the incidence of injury in parturients was approximately 1 per 25,000 for epidural blockade.25 More neurologic complications occurred with epidural than with spinal anesthesia. Additionally, more complications were found in surgical blocks than obstetric blocks. These injuries included spinal hematoma, epidural abscess, spinal cord lesions, subdural hematoma, permanent abducens paralysis, and Horner’s syndrome with facial pain.
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
