1) A history of the reliability of E.A. for labor should be confirmed.
2) The patient's back should be examined to ensure that an appropriate length of the catheter is still present. The catheter may be displaced by too much movement of the patient, inadequate taping or perspiration.
3) The first 10 ml of the local anesthetic should be injected with the patient on her side to exclude leakage of the catheter or superficial position of its tip, which can lead to subcutaneous crepitus or swelling.
4) If epidural injection of an adequate dose of a local anesthetic (e.g. 20 to 30 ml of 3% chloroprocaine) cannot achieve an adequate bilateral level of block (i.e. at least T6 dermatomal level), spinal anesthesia should be considered rather than struggling with an inadequate block and exposing the patient to its dangers.
The use of spinal anesthesia immediately after verification of inadequate E.A. and after administration of a large dose of a local anesthetic sometimes leads to an excessively high block. The mechanism of this occurrence is multifactorial. C.S.F. volume may have decreased owing to its compression by the epidurally injected large volume of local anesthetic; both techniques may have had an additive effect; or leakage of the epidurally injected local anesthetic into the subarachnoid space through the hole created in the dura. The dose of spinal should be reduced by one third, or the epidural block should be allowed to wear off before administering a spinal anesthetic.
II. Combined Spinal and Epidural Technique (CSE) (Chapter 62): This technique for both delivery and tubal ligation is an excellent alternative. The analgesia for early labor can be conducted using intrathecal 10 mcg sufentanil with or without 2.5 mg bupivacaine (1ml 0.25%). (1, 2) The analgesia begins almost instantaneously. Although the addition of a small dose of bupivacaine (2.5 mg) does not have any significant effect on motor power, it does prolong the duration and improve the quality of analgesia . After the spinal component of the block wears off, the epidural part can be initiated in the regular manner. To avoid a period of pain between the two parts of the technique, the epidurally injected local anesthetic should be started as soon as the patient feels discomfort. After delivery, E.A. can also be used for tubal ligation as described earlier.
III. Continuous Spinal Anesthesia (C.S.A): With C.S.A, analgesia for labor can be obtained by the use of an intrathecal narcotic with or without a local anesthetic as described above for C.S.E. After delivery, the level and intensity of the block can be achieved by titrating hyperbaric bupivacaine dosage (0.75% in 8.25% dextrose) to achieve a T4 dermatomal level. C.S.A. can be initiated from the start or an attempted E.A. can be converted to C.S.A. after inadvertent dural puncture. This alternative is simpler and safer than a repeated attempt to perform E.A.
References:
1. Abouleish A., Abouleish E, Camann W: Combined spinal-epidural analgesia in advanced labour. Can J Anaesth 1994; 41: 575-578.
2. Campbell DC, Camann WR, Datta S: The addition of bupivacaine to intrathecal sufentanil for labor analgesia. Anesth Analg; 81: 305-309.