Case Study
A healthy primigravidous patient with an uncomplicated pregnancy was induced at 41 weeks’ gestation. Her booking blood pressure was 125/75 mmHg. Following cervical ripening with prostaglandins, artificial rupture of membranes, and initiation of an oxytocin infusion, the patient requested neuraxial analgesia when at 5 cm of cervical dilation and in active labor. A combined spinal-epidural (CSE) was performed at the L3–L4 interspace using the loss of resistance to saline needle-through-needle technique. The spinal injectate consisted of ropivacaine 4.5 mg and sufentanil 2.25 µg. Following threading of the epidural catheter, patient-controlled epidural analgesia (PCEA) with a bolus of 4 ml and a 15-minute lockout was started immediately, combined with programmed intermittent boluses (PIEBs) of 10 ml hourly as a fixed maintenance regimen. The fixed bolus was administered 30 minutes after the initial spinal dose. The epidural solution was ropivacaine 0.1% with sufentanil 0.5 µg/ml.
The patient reported visual analogue scores (VAS) for pain of 0 within minutes and of below 20 mm throughout labor and delivery. The patient was positioned in the supine position with left lateral tilt by the anesthesiology trainee immediately after the CSE had been placed. Seven minutes after the spinal injection, a sustained fetal bradycardia (70 beats/min) was recorded on the cardiotocogram (CTG). Simultaneously, uterine hypertonicity was noted. Maternal blood pressure was 110/65 mmHg. A consultant anesthesiologist was called while the midwife administered 5 mg ephedrine as per standing order. The patient was turned to the full left lateral position, and the oxytocin infusion was temporarily stopped. Six minutes into the fetal bradycardia, the fetal heart rate improved and returned to normal. Gradually, oxytocin was restarted. Three hours later the patient delivered a healthy baby with good Apgar scores and umbilical artery blood gases. She was discharged home 24 hours after delivery.
Key Points
CSE combines the fast onset of a single-shot spinal with the flexibility of an epidural technique.
The use of CSE remains a topic of controversy owing to the perceived imbalance of risks and benefits
In this case, fetal bradycardia was associated with administration of intrathecal local anesthetic and opioid while the patient was positioned supine with left lateral tilt.
Ephedrine and better positioning resolved the fetal bradycardia by improving uteroplacental perfusion and uterine hypertonicity.
Discussion
Combined spinal-epidural anesthesia/analgesia (CSE) has been around for many decades.1 It combines the fast onset of a single-shot spinal with the flexibility of an epidural technique. The technique has also gained significant popularity in obstetric anesthetic practice both for labor analgesia and for anesthesia for cesarean delivery.1–3 However, it remains a topic of controversy.4
CSE in Labor
Advantages of CSE over Epidurals
Onset Time of Analgesia. The most obvious advantage of the CSE technique is the rapid onset of analgesia.5–9 Consistently, effective labor analgesia is accomplished within 5 minutes following the intrathecal injection of drugs. With epidurals, analgesia is usually achieved between 15 and 25 minutes following injection, but onset time demonstrates a wide interpatient variability, depending on factors such as parity and stage of labor.6–10 Especially in advanced labor, epidural analgesia is often delayed, requiring large doses and volumes of epidural solution. With CSE, onset time is short in most patients irrespective of the stage of labor.
Quality of Pain Relief: VAS Scores, Satisfaction, and Anesthesiology Intervention Rate and Local Anesthetic Consumption. Lower VAS scores for labor pain with CSE compared with epidural analgesia have been consistently reported, especially during the initial period after the spinal injection and up to 120 minutes.7, 8, 11 Throughout the entire labor duration, CSE also provides better-quality analgesia. Patients treated with conventional epidural analgesia are more likely to experience recurrent breakthrough pain than CSE-treated women and have more problems with unilateral analgesia.11, 12 The presence of a dural puncture may facilitate the passage of drugs from the epidural space to the CSF.12 Furthermore, with CSE, local anesthetic requirements are significantly reduced compared with low-dose conventional epidural techniques.7
Epidural Catheter Reliability
Various investigators noted that the reliability of epidural catheters following CSE was similar or increased compared with stand-alone epidural catheters,13 reflected by lower catheter replacement rates, fewer failures when topping up the epidural catheters for cesarean delivery, and less unilateral analgesia. Unfortunately, epidural catheter reliability was never a primary outcome variable, making interpretation of available data difficult. When using a CSE technique, a perfect midline approach is required to identify the subarachnoid space, and consequently, more epidural catheters are reliably positioned in the epidural space. Thomas et al.14 interestingly noted that when no CSF was obtained following attempted CSE, subsequently many more epidural catheters required replacement compared with those placed when CSF was noted.
Potential Risks of CSEs
Pruritus, Nausea, and Hypotension
Pruritus is the most common side effect of intrathecal and epidural opioids. No difference in the incidence of nausea has between reported when comparing the two techniques. As with any neuraxial technique, hypotension can occur following labor analgesia. Both CSE and conventional epidural analgesia have been associated with usually mild hypotension, which is easily treated.6 In routine clinical practice, it is important with CSE to avoid the supine position. In my hospital, patients are positioned in the completely left lateral position immediately after the CSE to avoid any effect of aortocaval compression.
CNS Infections
Some authorities claim that the risk of CNS infections is increased secondary to the breach of the dura. However, at present, there is no scientific evidence supporting this claim. Following 30,000 obstetric CSEs performed in my institution over the last 25 years, no CNS infection has been noted.
Neurologic Complications
As with any regional technique, the potential for nerve damage is present. Several case reports in pregnant women of damage to the conus medullaris when using CSE have been published.15 Especially with CSE, it is imperative to perform the block as low as possible because the conus medullaris might extend below the L2 vertebral body. Up to 5 percent of parturients can have a conus that extends lower than the L2 vertebral body. To avoid conus damage, careful attention to the correct interspace is required. It is also important to remember that anesthesiologists miss the correct interspace in more than 50 percent of cases when determining the interspace by anatomic landmarks.16
Post–Dural Puncture Headache (PDPH)
Because CSE includes a dural puncture, there is a theoretical risk of post–dural puncture headache (PDPH). The incidence is not increased over that with conventional epidural analgesia.17
Fetal Heart Rate Changes
Abnormal fetal heart rate recordings and fetal bradycardia are worrisome side effects that may follow any type of effective labor analgesia. More abnormal cardiotocographic readings following CSE than with systemic analgesia are reported.18 Also compared with conventional epidural analgesia, CSE induces more fetal heart rate abnormalities.6 It is important to note that neonatal and obstetric outcome is not affected by the use of CSE.
The mechanism of fetal heart rate abnormalities is not completely resolved, but uterine hypertonicity is crucial. As a result of rapid analgesia, an imbalance occurs between norepinephrine and epinephrine levels (due to different half-lives), resulting in a brief higher concentration of norepinephrine, which is a uterine stimulant, resulting in uterine hypertonicity. Potentially also involved are intrathecal opioids, which have been shown to produce more fetal heart rate changes when higher doses are used.6, 19
CSE for Cesarean Delivery
Spinal anesthesia is the technique of choice for cesarean delivery, but spinal-induced hypotension is also a common problem, with the potential for causing serious maternal and fetal morbidity.20 In recent years, a shift in understanding of the pathophysiology of spinal-induced hypotension has occurred, with less emphasis on venodilation and more on peripheral vasodilation.21 Three strategies exist to prevent/treat hypotension: fluid loading, vasopressors and reducing the spinal local anesthetic dose.22 Strategies to increase fluid loading have minimal success (e.g., left lateral tilt, crystalloid or colloid loading, and leg wrapping). Furthermore, prophylactic volumes of IV fluids increase the risk of iatrogenic pulmonary edema. Vasopressors are more successful in preventing hypotension, but they also have side effects such as myocardial ischemia, fetal acidosis, bradycardia, and hypertension. The third option, to lower the spinal anesthesia dose, is also possible, especially when a CSE technique is used. The goal of lowering the spinal dose is to avoid hypotension while preserving good-quality anesthesia.
Less Hypotension
Studies have demonstrated that lowering the spinal anesthesia dose to less than 9 mg and more than 5 mg bupivacaine can significantly reduce the incidence and severity of hypotension, as was demonstrated by Arzola et al. in a recent meta-analysis.23 Several additional studies not included in the meta-analysis by Arzola produced similar results.24–27
Vercauteren et al.24–26 published three trials in which they evaluated the incidence of hypotension following CSE anesthesia with 6.6 mg hyperbaric bupivacaine and 3.3 µg sufentanil. Hypotension occurred for both studies combined in only eight of 102 patients (8 percent).
Van de Velde et al.27 performed a randomized comparison of patients treated with CSE using either 6.5 or 9.5 mg hyperbaric bupivacaine combined in both groups with 2.5 µg sufentanil. Patients in the 9.5-mg group experienced more pronounced and longer hypotensive periods than those in the 6.5-mg group. The mean lowest recorded systolic pressure was higher in the 6.5-mg group (102 ± 16 mmHg versus88 ± 16 mmHg in the 9.5-mg group; p < 0.05). More patients in the 9.5-mg group experienced hypotension than in the 6.5-mg group (68 versus 16 percent; p < 0.05). In the 9.5-mg group, 15 patients required pharmacologic treatment for hypotension versus five in the 6.5-mg group.
McNaught and Stocks28 concluded that epidural saline could extend a spinal block. They also found that the CSE technique itself results in a higher sensory level of the block. This is explained by a change in epidural pressure when the epidural space is identified with the Tuohy needle because negative epidural pressure is neutralized by the open connection to atmospheric pressure, resulting in a reduction in dural sac volume, similar to the injection of fluid.
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