Learning Objectives:After participating in this continuing education activity, the provider should be better able to:
1. Describe the effects of epidural analgesia on labor progress, cesarean delivery rate, and fetal heart rate.
2. Identify the clinical presentation of adverse effects and complications associated with labor epidural analgesia.
3. Review management of adverse effects associated with epidural analgesia for obstetric patients.
This article is the second of 2 parts.
This is the second of 2 consecutive review articles discussing epidural analgesia for obstetric patients. The first article focused on the neurophysiology of pain, assessment of laboring patients for epidural analgesia, and the fundamental principles of labor epidural administration. In this review, we discuss the side effects and complications of labor epidural analgesia. The article focuses on the effects of labor epidural on the labor process and fetal heart rate, identification of complications associated with labor epidural analgesia, and management of these complications.
Effect of Labor Progress and Cesarean Delivery Rate
Labor Progress
The duration of the first-stage labor and the epidural effect is difficult to assess. The duration of the first stage is defined as the time from the beginning of regular uterine contraction to complete cervical dilatation. Women who received epidural analgesia may not feel the rectal pressure with complete cervical dilation and fetal descent. This may artificially prolong the duration of the first stage of labor by delaying cervical examination and timely recognition of complete dilatation. A recent meta-analysis addressed whether or not epidural analgesia prolongs the duration of the first stage of labor. The quality of the evidence was considered low with significant heterogeneity in the outcome.1
Epidural analgesia can prolong the second stage of labor. In one retrospective study of 15,500 deliveries, epidural analgesia significantly prolonged the second stage of labor to approximately 82 minutes (95th percentile).1 However, epidural analgesia does not significantly prolong the second stage of labor when a low concentration of local anesthetics (LCLA) is used. A recent meta-analysis did not show a significant difference in duration of the second stage labor between the group that had epidural analgesia with LCLA and the group that was administered nonepidural analgesia.2
Assisted Vaginal Delivery Rate
Epidural analgesia has been associated with high assisted vaginal delivery rate. The recent meta-analysis found that more women who received epidural analgesia experienced instrumental vaginal delivery, on the basis of 30 studies.3 However, when the authors reanalyzed the trials conducted after 2005, the higher rate of assisted vaginal delivery rate was no longer present, which suggests that modern epidural medication with LCLA may not cause an increase in instrumental vaginal delivery rate. The studies comparing early versus late epidural analgesia did not show any difference in assisted vaginal delivery rate (Table 1).
Cesarean Delivery Rate
About 32% of pregnant women deliver by cesarean delivery in the United States. Multiple randomized controlled trials have been conducted to assess the effect of epidural analgesia on the cesarean delivery rate and have not demonstrated a significant difference when compared with nonepidural analgesia or no analgesia.1 In a population-based, retrospective cohort study from the Netherlands, there was no significant association between epidural analgesia and cesarean delivery rate. A meta-analysis of the impact of epidural analgesia before and after the availability of epidural analgesia did not show any significant change in the cesarean delivery rate with an increase in epidural analgesia. Overall, the epidural analgesia has no significant effect on the cesarean delivery rate.4
Fetal Heart Rate Effects
Fetal effects of epidural analgesia can be divided into direct and indirect effects. Most of the medications used to provide epidural analgesia readily crosses the placenta. However, there is little evidence of the direct effects of these drugs when administered via the epidural route. Transient changes in fetal heart rate variability and periodic decelerations have been reported during labor epidural analgesia in the absence of hypotension.5-7 These fetal heart tone changes are most likely the result of a reduction in maternal circulating catecholamines and loss of sympathomimetic-induced relaxation of the myometrium.8 Data suggest that, in the absence of maternal hypotension, epidural local anesthesia has been shown to have minimal effect on umbilical vasculature and has been associated with improved intervillous blood flow and neonatal acid-base status.1,9,10 Epidural opioid administration as a continuous infusion rarely results in accumulation and neonatal depression.
Indirect effects of epidural analgesia on fetal well-being primarily result from the effect on maternal physiologic parameters. Sustained untreated maternal hypotension from sympathetic blockade can lead to fetal hypoxia, acidosis, and bradycardia. Maternal severe respiratory depression resulting from systemic effect of opioids can lead to fetal hypoxia and acidosis. More common is fetal bradycardia after initial neuraxial anesthesia due to decreased plasma concentration of catecholamines. This is more commonly observed after administration of intrathecal sufentanil as a component of combined spinal epidural for labor analgesia. However, it was not reported to increase the rate of cesarean delivery.11
Side Effects of Labor Epidural Analgesia
Maternal Hypotension
Aortocaval compression by the gravid uterus against lumbar vertebral bodies leads to a reduction in the venous return to the heart and is responsible for a 30% decrease in cardiac output in the supine position at term. Aortocaval compression also leads to an increase in the venous pressure in the lower extremities, decreasing its blood flow. Blood flow in the upper extremities is normal. However, only 10% to 15% of obstetric patients experience supine hypotensive syndrome because most obstetric patients develop collateral venous flow through the interosseous, azygos, vertebral, paravertebral, and epidural veins to maintain venous return. Patients with conditions such as multiple gestation, polyhydramnios, and fetal macrosomia are more likely to experience supine hypotensive syndrome during the third trimester. Epidural analgesia induces a sympathetic block, which results in hypotension due to peripheral vasodilation. The vasodilation resulting from epidural block exacerbates the supine hypotension syndrome. The resulting vasodilation leads to a reduction in the venous return to the heart, with the resultant reduction in stroke volume and cardiac output. The incidence of hypotension after initiation of neuraxial analgesia during labor is up to 24%. It is important to note that maternal blood pressure is usually measured in the upper extremities. This measurement may reflect the effects of vena caval compression but not aortic compression, which can directly reduce uterine blood flow despite a normal reading in the upper extremity. A 15- to 30-degree left lateral tilt of the patient is recommended to relieve compression by the gravid uterus. Left uterine displacement may not consistently reduce the occurrence of maternal hypotension; however, it has been shown that it leads to higher umbilical arterial blood pH and better neonatal outcomes than the supine position, indicating that maternal blood pressure measured at the level of the brachial artery may not always predict uteroplacental perfusion.12
It is prudent to attempt at preventing neuraxial-induced hypotension during epidural placement. Interventions to maintain maternal blood pressure during epidural analgesia include maintaining a 15-degree left uterine displacement during the infusion of epidural medications, administration of IV fluid preload, using lower leg compression, and IV ondansetron. If hypotension ensues after administration of the loading dose, the patient should be immediately placed in a 15- to 30-degree left lateral tilt. A noninvasive blood pressure measurement should be obtained after 1 minute and every 1 minute thereafter, until normalization of maternal blood pressure. In many occasions maintaining the left lateral tilt is sufficient to improve maternal blood pressure. If maternal hypotension persists beyond 1 minute and despite a lateral tilt, administration of IV fluids and the use of vasopressors should be implemented immediately to avoid compromise of the uteroplacental blood flow. Phenylephrine is considered the first-line drug, but ephedrine is still used. Phenylephrine leads to reflex bradycardia, so it is more appropriate for patients with tachycardia or normal heart rate. Ephedrine leads to an increase in heart rate and thus is more appropriate for patients with significant bradycardia. A recent study suggested norepinephrine infusion or bolus can be used safely.13 Fetal heart tones should be monitored continuously during the administration of labor epidural medications. The obstetric team should be notified and close observation of fetal heart tones should occur until hypotension resolves.
Postdural Puncture Headache
Postdural puncture headache (PDPH) is induced by loss of cerebrospinal fluid (CSF) due to inadvertent dural puncture. Overall, the risk of accidental dural puncture with epidural insertion in parturients is 1.5% approximately, and about half of them develop PDPH.2 PDPH is diagnosed with a headache that has developed within 5 days of the dural puncture and disappears up to 48 hours after an epidural blood patch (EBP) or spontaneously within 1 week. The pathognomonic symptom is a positional headache that worsens within 15 minutes of sitting or standing and is relieved within 15 minutes in the supine position. Other symptoms of PDPH include neck stiffness, tinnitus, hearing alteration, photophobia, blurry vision, and nausea.14 Loss of CSF volume and pressure may cause caudal displacement of cranial contents and an increase in blood flow and vasodilation to compensate for the intracranial hypotension. Blurry vision and other visual disturbances occur due to the traction of cranial nerves (III, IV, and VI). Hearing alteration, vertigo, and tinnitus may also result from the transmission of abnormal CSF pressure to the perilymph of the cochlea and disruption of hair cells within the inner ear. The complications of PDPH include the difficulty to perform the activities of daily living, increase in hospital length of stay, and neurologic complications such as subdural hematoma, dural sinus thrombosis, hearing loss, or chronic headache.14,15
Treatment of PDPH includes hydration, EBP, sphenopalatine ganglion block, and drug therapy such as caffeine, gabapentin, or a theophylline.14,15 An EBP is the most reliable treatment for PDPH. EBP entails injecting autologous blood into the epidural space under strict sterile conditions. The exact mechanism of action of alleviation of PDPH symptoms with EBP is not completely understood. Possible mechanisms include increasing the pressure in the epidural space to minimize CSF leak and restore CSF pressure subsequently. Proinflammatory effect accelerating healing of dural tear is another mechanism. Alternatively, a transnasal sphenopalatine ganglion block can relieve PDPH successfully.16 It is important to follow up with the patient if any symptoms develop. Early diagnosis with appropriate management is crucial to avoid further complications related to PDPH. Delaying EBP to at least 24 hours after the dural puncture may increase the likelihood of treatment success.
Intrathecal Injection
Unrecognized intrathecal injection via epidural needle or catheter can occur. The incidence of the high neuraxial blockade after the initiation of epidural analgesia in obstetric patients is highly variable. It ranges between 1:4567 and 1:16,200.4,17 If a large dose of epidural anesthetics is administered unintentionally into intrathecal space, it may cause respiratory distress, hypotension, loss of consciousness, cardiac arrest, and fetal distress. The mainstay of high neuraxial blockade management is cardiopulmonary support, which consists of maintaining an airway, ventilation with 100% oxygen, vasopressors, IV fluid administration, and avoid aortocaval compression. CSF lavage was reported and showed the effectiveness of managing high spinal anesthesia.18 However, there is only limited evidence available to support the lavage technique and safety concerns such as infectious risks.
Intravascular Injection and Local Anesthetic Systemic Toxicity
The incidence of intravascular injection of local anesthetics is approximately 1.04 to 1.8/1000, and about 13% of local anesthetic systemic toxicity (LAST) cases occur as a result of neuraxial blockade.4,19 Neurologic symptoms of LAST include restlessness, dizziness, tinnitus, perioral numbness, difficulty speaking, seizures, and unconsciousness. Cardiac toxicity manifests as bradycardia, ventricular dysfunction, ventricular tachycardia and fibrillation, and cardiac arrest.4 The management of LAST in obstetric patients is listed in Table 2.4,20 To prevent LAST, incremental local anesthetic administration and intermittent aspiration should be used. Aspiration and test dose after placing an epidural catheter can detect accidental intravascular placement. Low-dose epinephrine in the test solution can increase the heart rate more than 10 beats/min and the systolic blood pressure more than 15 mm Hg, if the dose is administered intravascularly.19 Sensory level should be checked after the epidural, especially if the local anesthetic solution contains opioid such as fentanyl. Lack of a sensory level after the loading dose may be an indication of intravascular placement of the catheter and medication. In this case, the patient may obtain pain relief from the systemic action of opioids, but LAST ensues over time due to systemic accumulation of the local anesthetic.
Failure
Epidural failure has been defined as those epidurals that either are aborted or do not provide analgesia after 45 minutes' postplacement.21 In a retrospective study of more than 19,000 deliveries, the overall failure rate in patients receiving either epidural or combined spinal epidural anethesia was 12%.22 Some risk factors associated with increased likelihood of epidural failure include operator inexperience, higher patient body mass index, lack of patient cooperation, history of epidural failure, and prolonged labor periods.23
Back Pain
Although long-term back pain is uncommon, patients with a history of low back pain are more likely to experience back pain after epidural analgesia.24 Short-term back discomfort is more common. Back pain is less common in nulliparous women.24
One-Sided Block
A unilateral block can occur as a result of catheter misplacement (whether off midline or threaded too far into the epidural space) or patient positioning favoring one side (less likely). The most appropriate length of the epidural catheter has been shown to be 5 cm in the epidural space. Catheter depth exceeding 5 cm in the epidural space may lead to a higher incidence of unilateral sensory block.25 Unilateral sensory block can be managed by increasing demand bolus dose or withdrawing the epidural catheter out of the epidural space to a length of 4 to 5 cm under strict sterile conditions.
Infection
Epidural abscess is a rare but significant complication of epidural analgesia. The reported incidence of epidural abscess after labor epidural analgesia for obstetric procedures is 1 in 302,757 procedures.26 Risk factors for epidural abscess include prolonged catheterization periods, administration of opioid without local anesthetic, traumatic insertion, diabetes, immunosuppression, and the presence of blood in the epidural space. Symptoms of epidural abscess usually manifest between 4 and 10 days after catheter removal. Symptoms include fever and back pain. Neurologic symptoms such as radiating pain, leg weakness, and bladder dysfunction indicate significant compromise of the neural elements and warrant an urgent surgical intervention. Treatment of epidural abscess includes antibiotics (2-4 weeks), percutaneous, or surgical drainage (laminectomy).
Hematoma
Although very rare in obstetric patients, the risk of spinal hematoma is increased in cases of maternal coagulopathy and anticoagulation use. In a 2016 review of over 2 million laboring patients, the incidence of spinal hematoma was estimated to be 0.6 in 100,000.27 Even rarer is the occurrence of an intracranial hematoma. Risk factors for epidural hematoma include traumatic placement, difficult placement, coagulopathy, therapeutic anticoagulation, spinal deformity, and spinal tumors. Manifestations of epidural hematoma include neurologic deficits and back pain. Early identification using MRI, neurosurgical consultation, and proper surgical evacuation while correcting underlying coagulopathy is crucial to avoid permanent neurologic deficits.
Neurologic Injury
Neurologic injury attributed to epidural is extremely rare. Also, most neurologic deficits associated with epidural anesthesia are transient resolving within 72 hours. More common are nerve injuries associated with labor and delivery including fetal head compression, instrumentation, or patient positioning in lithotomy.
Pruritus
Pruritus is the most common side effect associated with administration of neuraxial opioids. The incidence and severity are higher when opioids are administered via the intrathecal rather than the epidural route. Most commonly it affects the head and neck, especially the face. Pruritis associated with epidural opioid is usually not severe and is self-limited, requiring no intervention. Severe pruritus can be effectively treated with small doses of IV nalbuphine without affecting the analgesic effect of epidural opioids.28
Maternal Fever
Multiple studies report an association between the use of epidural analgesia and maternal fever. The increase in maternal temperature is usually around 1[degrees]C and rarely exceeds 38[degrees]C. This rise in body temperature was noticed to be greater in patients with warmer ambient temperatures.29 The cause of this phenomenon is not completely understood. Although the significance of these temperature changes remains unclear, a subsequent rise in fetal temperature can occur making the diagnosis of fetal infection more of a challenge.
Urinary Retention
Urinary retention is a side effect of neuraxial blockage due to blockade of sacral nerve roots S2, S3, and S4. These sacral nerve roots control the detrusor muscle and internal and external sphincter function.1 Urinary retention is less common with LCLA solutions compared with higher concentration solutions. Urinary retention usually ensues when the epidural block is established. If the patient is unable to ambulate, void, or perceive bladder distension, a bladder catheter should be placed.
Conclusion
Knowledge of the clinical presentation and management of the side effects and complications of epidural analgesia in obstetric patients is pivotal to maternal and fetal safety. All disciplines involved in the care of the obstetric patient should effectively communicate to promptly identify and manage these complications.
Practice Pearls
* Labor epidural analgesia has not been shown to increase the incidence of cesarean delivery.
* Epidural analgesia has been shown to prolong the second stage of labor.
* Epidural analgesia has not been shown to increase the rate of assisted instrumental vaginal delivery.
* The most reliable treatment of PDPH is EBP performed at least 24 hours after the dural puncture.
* Management of a one-sided epidural block includes increasing the volume of the demand bolus or pulling the catheter out of the space to maintain 4 to 5 cm in the epidural space.
* Patients experiencing fever, back pain, and lower extremity neurologic symptoms within 4 to 10 days after epidural catheter removal should receive an urgent neurologic evaluation to diagnose and treat epidural abscess.
* Patients with back pain and neurologic defects after resolution of the effect of epidural medications should receive an emergency neurologic evaluation and MRI to exclude spinal hematoma.
* Patients with suspected LAST should be managed by supporting airway breathing, and circulation. Lipid emulsion should be administered intravenously at the first sign of LAST.
* If the patient receiving labor epidural analgesia is unable to ambulate, void, or perceive bladder distension, a bladder catheter should be placed.
* Patients receiving epidural opioids and reporting severe pruritus can be effectively treated with small doses of nalbuphine without significantly affecting the analgesic effect of epidural opioids.
REFERENCES