An epidural is a common and highly effective method of regional anesthesia used to manage pain during labor. The procedure involves placing a thin, flexible catheter into the epidural space, which is just outside the protective membrane of the spinal cord. This catheter delivers a continuous flow of pain-relieving medication to the nerves responsible for sensation in the lower body.
Sustaining Pain Relief: Continuous Infusion and Bolus
The goal of the initial epidural placement is to establish a single, long-lasting delivery system for analgesic medication. Once the catheter is secured, the anesthesiologist uses it to maintain a consistent level of pain control. This maintenance phase relies on two primary techniques for medication delivery.
Continuous Infusion and Bolus
One common method is the Continuous Epidural Infusion (CEI), which involves a slow, steady drip of a local anesthetic, often combined with an opioid, delivered by an automated pump. Another technique is Programmed Intermittent Epidural Bolus (PIEB), where the pump automatically injects a small volume of medication at regular intervals. The bolus technique achieves a more uniform spread of the medication across the epidural space compared to continuous infusion.
Many systems also incorporate Patient-Controlled Epidural Analgesia (PCEA). This allows the patient to self-administer a small, pre-set dose of medication on demand when they feel a breakthrough in pain. Since the initial catheter remains in place, these techniques are all considered part of the single epidural procedure.
Addressing Epidural Failure and Re-placement
While an epidural is highly effective, the initial placement may sometimes be inadequate, or the catheter may cease to function optimally during labor. Intervention is necessary in these cases.
Causes of Failure
A common issue is an asymmetric block, often referred to as a “hot spot,” where one side of the body continues to experience pain while the rest is numb. This can occur if the catheter tip is positioned laterally, causing the medication to pool on one side of the epidural space. Failure can also result from catheter migration, where the thin tube shifts after its initial placement, leading to a complete loss of pain relief.
An anesthesiologist may first attempt to fix the issue by injecting a larger, corrective dose of medication through the existing catheter or by slightly adjusting its position. If these corrective measures fail to restore effective pain relief, the catheter is deemed non-functional and requires a complete re-insertion. This re-insertion involves a new needle stick and the placement of a new catheter, which is considered a second, distinct procedure. Re-placement is a viable and necessary option when the initial attempt is unsuccessful.
Timing Constraints and Safety Considerations
There is no strict medical milestone that dictates the latest point an epidural can be administered. An epidural can be safely requested at any stage of labor, and waiting does not necessarily improve outcomes or shorten labor duration. The true constraint for receiving an epidural or a re-placement is the speed of labor progression. If the mother is progressing very rapidly, there may not be enough time for the anesthesiologist to perform the procedure and for the medication to take effect before delivery.
While the procedure is generally safe, multiple attempts to place the epidural needle, which would occur in the event of a re-placement, carry a slightly increased chance of complications. The most recognized risk is an accidental dural puncture, where the needle enters the membrane surrounding the spinal cord, which can lead to a post-dural puncture headache. Anesthesiologists work quickly to resolve issues, but there is a practical limit to the number of re-insertions they will attempt before considering alternative pain management options.