Case Study
A 28-year-old primigravida at 39 weeks of gestational age with 5 cm of cervical dilation in labor requested epidural analgesia for painful contractions. She was noted to be obese by the obstetric team with a body mass index (BMI) of 40 kg/m2 but no other comorbidities .The anesthesiologist arrived and assessed the patient, after which he explained the procedure and took informed consent. He started the procedure using a 16-gauge epidural needle with a loss of resistance to saline technique with the patient in the left lateral position. After multiple attempts, he was unable to identify the epidural space and therefore tried again with the patient in the sitting position. After two attempts, he successfully identified the epidural space at 7 cm from the skin at the L3–L4 level using a midline approach. He then threaded a multiorifice epidural catheter, leaving 5 cm within the epidural space (12 cm at the skin surface). He went on to confirm the epidural catheter position with a negative aspiration to CSF or blood. He then asked the patient to sit upright and then to lie down in the left lateral position so that he could securely fix the epidural catheter with a clear sterile dressing. A patient-controlled epidural analgesia (PCEA) pump was started using 0.1% levobupivacaine with 2 µg/ml fentanyl (basal rate of 5 ml/h and a PCEA demand dose of 10 ml with a lockout time 20 minutes). The patient became comfortable within 20 minutes. Unfortunately, after 3 hours, she started complaining of pain in her right lower abdomen. The anesthesiologist assessed her and decided to give her a bolus dose with 10 ml 0.125% levobupivacaine manually. He advised her to lie down in the right lateral position for approximately 20 minutes. Her pain was relieved after 15 minutes. The patient continued to be comfortable and extremely happy with her pain relief and used the PCEA for additional analgesia until the delivery of her baby several hours later.
Key Points
Proper positioning of the patient during an epidural procedure is important.
Securing the epidural catheter after the procedure can prevent catheter movement within the epidural space, which sometimes results in suboptimal analgesia.
Breakthrough pain can be managed occasionally by changing the patient’s position, withdrawing the epidural catheter, and delivering a manual bolus of low-dose epidural local anesthetic mixture such as 0.1% levobupivacaine with 2 µg/ml fentanyl.
Follow-up of patients with epidurals in the delivery suite is advisable at regular intervals during labor so that timely interventions can be made if needed for inadequate analgesia.
Discussion
It is not uncommon to have a failed epidural that has previously been administered for labor analgesia. In the literature, the largest case series, which was published in 2004 by Pan et al.,1 reports an overall failure rate of 12 percent, with 6.8 percent of patients requiring reinsertion of the epidural catheter. Other studies by Paech et al.,2 Eappen et al.,3 and Crawford4 show failure rates of 4.7, 13.1, and 15.5 percent, respectively
There can be different reasons for failed epidural analgesia.
Predicting Epidurals that May Become Suboptimal or Fail
A study by Lecoq et al.5 in 456 labor epidurals showed that a lack of effect of the first epidural drug dose, posterior presentation of the fetus, radicular pain during catheter insertion, and a duration of labor of more than 6 hours are risk factors for inadequate analgesia. Another trial by Agaram et al.6 identified a cervical dilation of more than 7 cm, epidural insertion by a trainee, history of opioid tolerance, and a previous failed epidural were risk factors. A systematic review and meta-analysis of observational studies by Bauer et al.7 regarding risk factors for failed conversion of labor epidural analgesia to provide anesthesia for cesarean delivery showed that an increased number of epidural drug boluses, care provided by a nonobstetric anesthetist, and an enhanced urgency for cesarean delivery are predictors of failed conversion. In 2006, Orbach-Zinger et al.8 showed that the chances of a failed epidural top-up for cesarean delivery is higher in younger, more obese parturients with a greater gestational age. These patients also required more epidural top-ups during labor and had high Visual Analogue Scale (VAS) scores 2 hours before their cesarean delivery.
Improving Techniques for Labor Epidural Analgesia
Maternal Position during an Epidural Procedure: Sitting versus Lateral
There is no conclusive evidence in the literature that patient positioning affects the efficacy of subsequent epidural analgesia. Although the sitting position makes it much easier to identify the midline and epidural space, it may not be comfortable for patients experiencing labor pain. The sitting position may increase the chance for orthostatic hypotension. The epidural venous plexus is also thought to be more engorged in this position, leading to a higher rate of venous puncture with the epidural catheter. Although the lateral position may be more comfortable for the patient, it is often technically difficult for the obstetric anesthetist, especially in obese patients, to locate the midline and the epidural space.
Loss-of-Resistance Technique: Air versus Saline
There are controversies regarding the loss-of-resistance (LOR) technique with saline or air and the subsequent success of epidural analgesia. A 2011 meta-analysis suggested an increased risk of unblocked segments when loss of resistance to air (LORA) was used due to air bubbles in the intervertebral foramina.9 However, another study by Segal and Arendt10 showed that there was no significant difference in neuraxial block success whether you use loss of resistance to air or saline. These days, the consensus appears to be that anesthetists should always use a technique (LORA or LORS) that is familiar to them.
There are other devices such as the Epidrum or Episure that have been used to identify the epidural space. A trial comparing the Epidrum with a standard LOR technique for inserting an epidural for labor analgesia did not show any difference in success or complication rate.11 A 2008 pilot study of 325 patients compared the Episure Auto Detect syringe with a glass syringe.12 Eight residents performed 291 procedures (90 percent) and two consultants performed 34 procedures (10 percent). Overall, epidural analgesia failed in five subjects in the glass syringe group, whereas there were no failures in the spring-loaded Episure Auto Detect syringe group (P = 0.025).
Type of Epidural Catheter
There is evidence in the literature that polyurethane multiorifice catheters have a lower risk of inadequate analgesia.13 Segal et al.14 showed that replacement rates were less when multiorifice catheters were used with fewer episodes of paresthesia when compared with single-orifice catheters.
Wire-reinforced epidural catheters are available that are designed with fewer coils in the distal tip, which reportedly confers greater flexibility to minimize paresthesias and perforations of the dura mater and epidural blood vessels. There are in addition distal and proximal flashback windows for visualization of CSF or blood. A few studies have compared traditional multiport catheters and the newer wire-reinforced catheters in terms of both analgesic efficacy and the incidence of complications. In a prospective quality assurance study, Jaime et al.15 compared clinical complications in 2,612 obstetric patients who received epidural analgesia with either a 20-gauge closed-tipped multiport (three lateral ports) nylon catheter or a 19-gauge open-end uniport spring-wound polyurethane catheter. Although the incidence of unsatisfactory block was similar in both groups, the incidence of paresthesias, venous cannulation, and reinsertion related to venipuncture was significantly higher in the patients who received the non-wire-reinforced nylon catheters.
Combined Spinal-Epidural (CSE) or Epidural
There is good evidence that a CSE technique provides more rapid and reliable analgesia initially than an epidural technqiue16 (see Chapter 7). However, this initial benefit in terms of analgesia may not apply for the duration of labor. Many studies demonstrate lower VAS scores for labor pain with CSE compared with epidural. There are many, mainly retrospective trials that show that the reliability of epidural catheters following CSE is significantly increased compared with an epidural technique alone. Interestingly, a recent Cochrane review16 found no difference in overall maternal satisfaction despite a slightly faster onset time with a CSE technique. Fetal bradycardia is often reported to be a significant drawback after a CSE for labor analgesia. Following a meta-analysis of 24 trials demonstrated an increase in the incidence of fetal bradycardia in patients receiving intrathecal opioids, some clinicians recommended avoiding intrathecal opioids when a nonreassuring fetal status is present before performing a CSE technique for labor analgesia.17 However, a 2014 study by Patel et al.18 showed no significant difference in fetal heart rate changes, Apgar scores, or umbilical artery and vein acid-base status between epidural and CSE groups.
Epidural Catheter Length to Be Left within the Epidural Space
Berlin et al.19 found that leaving 5 cm of a multiorifice catheter within the epidural space provided superior analgesia compared with 3 and 7 cm. A nonobstetric study by Afsan et al.20 showed no change in postoperative pain scores in patients who underwent abdominal hysterectomy between groups with 3, 5, or 7 cm of epidural catheter left in the epidural space. A patient in the 7-cm group had unilateral sensory analgesia. Of note, there was a much higher rate of epidural catheter dislodgement in the 3-cm group. It seems that the most appropriate length should be 5 cm.
Fixation of the Epidural Catheter
The position of the patient during fixation of an epidural catheter is important. The evidence from the literature21 shows that the epidural catheter position within the epidural space can change significantly with patient movement. If the epidural catheter is secured while the patient is sitting up in a flexed position, the catheter may be pulled outward later once the patient straightens her back because there is no space for soft tissue movement. Therefore, it is important to keep the patient in a neutral position (whether the patient is sitting or lying down in a lateral position for her initial epidural procedure) before fixing the epidural catheter to prevent dislodgement. This may be more important in obese patients.
A randomized, controlled trial investigated the efficacy of Epi-Fix, LockIt Plus (Figure 5.1), and Tegaderm as fixation devices for intrapartum epidural catheters and showed that those secured with the LockIt Plus device exhibited less epidural catheter migration compared with fixation using either Epi-Fix and Tegaderm clear adhesive dressing.22
