Combined spinal-epidural analgesia (CSE) has gained in popularity over the past decade. The epidural space is identified in the conventional manner with a Touhy or Weiss needle, and then a 26 or 27 gauge (5 inch) pencil point needle is passed though the epidural needle until the dura is pierced, signified by the free return of cerebrospinal fluid. At this point, medication consisting of a narcotic (typically sufentanil or fentanyl) alone or in combination with a small amount of local anesthetic, usually bupivacaine, is injected into the subarachnoid space. The spinal needle is removed and then a catheter is placed into the epidural space. There are also specialized epidural/spinal combination needles available; in which the epidural needle has a special hole or channel through which the spinal needle can pass1.
This technique achieves the goals of rapid onset of analgesia with minimal effects on lower extremity motor function, to a much greater extent than can be accomplished with a conventional epidural. This technique also allows more reliable placement of the epidural catheter. CSE is effective in late, rapidly progressing labor, and it permits the patient to ambulate if she desires to2. The disadvantages of the technique include pruritus, transient fetal bradycardia, hypotension, and respiratory depression. In addition, since the catheter is not routinely dosed until patient discomfort returns, catheter function is not immediately confirmed after placement; this may pose a management dilemma if urgent cesarean section is required.
The earliest reference to CSE described a technique that consisted of injecting local anesthetic into the epidural space and subsequently into the subarachnoid space3. When CSE was rediscovered for laboring parturients, narcotics alone were used 4, 5,6. Early studies described the use of morphine 0.25 mg. This provided prolonged analgesia, but delayed respiratory depression was a concern. Fentanyl 25 mcg and sufentanil 10 mcg proved to be effective analgesics with less risk of respiratory depression. Fentanyl and sufentanil were both found to produce significant pruritus, which could be treated with diphenhydramine, but usually more effectively with naloxone. The analgesia produced by these agents lasted from 90 to 120 minutes. In the earliest version of this technique, medications were not injected via the epidural catheter until the patient began to complain of pain. Attempts to prolong the duration of intrathecal analgesia, and thus the time to initial dosing through the catheter, led to the supplementation of the narcotic with a small amount of local anesthetic (bupivacaine 1.25-2.5 mg, ropivacaine 1 to 2 mg). This did indeed lengthen the duration of analgesia7,8. It was discovered, however, that even with the addition of local anesthetic to the intrathecal narcotic, there would be patients, whose length of labor exceeded the duration of analgesia. These patients would require supplementation via the catheter. Many practitioners began to initiate dilute local anesthetic/opioid infusions soon after the placement of the epidural. This is a safe practice as long as the level of sensory blockade levels is closely monitored9. With the immediate initiation of an epidural infusion, the duration of analgesia after the initial dose is less important. This permits the use of lower doses of intrathecal narcotic10. This should decrease the incidence of side effects, since in many cases these are dose related11.
The technique used in our practice has evolved over time. We have found that fentanyl 10-15 mcg or sufentanil 5-7.5 mcg in combination with bupivacaine 1.5-2.5 mg or ropivacaine 1-2 mg provides rapid, reliable analgesia. This is followed by a standard lidocaine-epinephrine test dose, and an infusion of bupivacaine 0.125% with fentanyl 2 mcg/ml (at a rate of 8 to 10 cc/hr depending on the analgesic level) is then initiated. We have found that this regimen provides good long term analgesia and allows ambulation if desired in most cases. An additional suggested advantage of CSE in early labor is more rapid cervical dilation in nulliparous women12. It has also been suggested that return of CSF via the spinal needle provides more reliable identification of the epidural space13.
Most of the practitioners who are opposed to the routine use of CSE cite its side effects and complications. I will address each of these concerns
1. Pruritus: While common, the incidence appears to be decreased when smaller initial doses of narcotic are used. Treatment with diphenhydramine or naloxone is effective, but seldom required. Patient satisfaction with the rapid onset and high quality of analgesia outweighs this relatively minor complication.
2. Respiratory depression: The incidence has been reported to be 0.01% to 0.1%. Respiratory depression usually occurs soon after drug administration. Close monitoring for 15-30 minutes after drug administration should ensure that appropriate treatment will be initiated before respiratory compromise occurs.
3. Hypotension: Most of the recent studies have shown that the incidence of hypotension is similar to that for conventional epidural analgesia14, 15. In our practice, the need for ephedrine appears to be greater in patients receiving conventional epidural analgesia.
4. Transient fetal bradycardia: It has been suggested that the cause of fetal bradycardia is the sudden decrease in circulating catecholamines secondary to the rapid onset of profound analgesia. As epinephrine levels decrease, its beta agonist effects rapidly diminish as well, especially tocolytic effects on uterine muscle. This will potentially lead to uterine tetany, which will decrease uterine blood flow and fetal oxygen delivery, leading to fetal bradycardia 8, 14,15,16. This is typically transient and can be treated with nitroglycerin or terbutaline 17,18. The incidence is small and it is extremely unusual for this bradycardia to lead to cesarean delivery. Changes in fetal heart rate have been reported to be extremely common during conventional epidural analgesia14, 15,16.
5. Unconfirmed epidural function: It is true that if a catheter has not been dosed, it is not certain that it will function if rapid extension of the block is necessary for emergent cesarean section. However, even apparently well-functioning labor epidurals occasionally fail to provide adequate anesthesia for surgery. I have been able to top up CSE catheters as reliably as conventional epidural catheters for urgent C-section. Additionally, one study confirmed an overall decreased failure rate for epidural catheters placed via CSE for both labor analgesia and surgical anesthesia19. In our practice, we have found both a decreased need to replace epidurals inserted with the CSE technique, as well as a decreased incidence of one-sided blocks.
In conclusion, CSE provides rapid and reliable labor analgesia while preserving lower extremity motor function, and in many cases allowing ambulation. The side effects and risks are comparable to conventional epidurals and are easily manageable. For this reason, combined spinal epidural analgesia should be offered to all routine laboring parturients.
Vernon Ross, M.D.
Virginia Commonwealth University/Medical College of Virginia