The epidural space is identified with a loss-of-resistance technique The epidural catheter is threaded 3 to 5 cm into the epidural space
A test dose of 3 mL of 1.5% lidocaine with 1 :200,000 epinephrine or 3 mL of 0.25% bupivacaine with 1 :200,000 epinephrine is injected after careful aspiration to avert injection and after a uterine contraction. This minimizes the chance of confusing tachycardia that results from labor pain with tachycardia from intravenous injection of the test dose.
If the test dose is negative, 10-15 mL of 0.0625-0.125% bupivacaine are injected to achieve a sensory TlO level.
Ater 15 to 20 minutes, the block is assessed using loss of sensation to cold or pinprick. If no block is evident, the catheter is replaced. If the block is asymmetrical, the epidural catheter is withdrawn 0.5 to 1s.0 cm and an additional 5 to 10 mL of 0.0625-0.125% bupivacaine is injected. If the block remains inadequate, the catheter is replaced.
The woman is positioned in the lateral or semilateral position to avoid aortocaval compression.
Subsequently, maternal blood pressure is recorded every 5 to 15 minutes. The fetal heart rate is monitored continuously. The level of analgesia and intensity of motor blockade are assessed at least hourly.
Reproduced with permission from Glosten B: Local anesthetic techniques. In Chestnut DH (ed): Obstetric Anesthesia: 2nd ed. St Louis, Mosby, 1999.
1988). As with spinal blockade, close monitoring, including the level of analgesia, is imperative and must be performed by trained personnel. Appropriate resuscitation equipment and drugs must be available during administration of epidural analgesia.
Higher or Total Spinal Blockade. In general, complications with epidural analgesia are similar to those with spinal analgesia (see Table 25-5). Dural puncture with inadvertent subarachnoid injection may cause total spinal blockade. Sprigge and Harper (2008) cited an incidence of 0.91 percent recognized accidental dural punctures at the time of epidural analgesia in more than 18,000 women. Personnel and facilities must be immediately available to manage this complication as described earlier (p. 491). In other aspects, however, complications are unique and inherent to epidural analgesia use.
Inefective Analgesia. Using currently popular continuous epidural infusion regimens such as 0.125-percent bupivacaine with 2-�g/mL fentanyl, 90 percent of women rate their pain relief as good to excellent (Sharma, 1997). lternatively, a few women ind epidural analgesia to be inadequate for labor. In a study of almost 2000 parturients, Hess and associates (2001) found that approximately 12 percent complained of three or more episodes of pain or pressure. Risk factors for such breakthrough pain included nullipariry and heavier fetal weights. Dresner and colleagues (2006) also reported that epidural analgesia was more likely to fail as body mass index increased. If epidural analgesia is allowed to dissipate before another Injection of anesthetic drug, subsequent pain relief may be delayed, incomplete, or both.