Continuous Spinal Anesthesia

Continuous spinal anesthesia has many potential advantages when compared with single-shot spinal or epidural techniques. The classic technique required the use of large-bore epidural needles; newer techniques use a 32-gauge microcatheter inserted through a 26-gauge spinal needle.^[189] The technique rapidly gained in popularity despite technical difficulties, but as previously described, it was abandoned after withdrawal of these catheters by the FDA. The advantages of continuous spinal anesthesia, however, remain, and macrocatheters (e.g., placing an epidural catheter intrathecally) can be used in high-risk parturients. To perform continuous spinal anesthesia, the anesthesiologist pierces the dura with an epidural needle and then threads the epidural catheter 3 to 4 cm within the intrathecal space. Catheter placement can be tested by aspiration of CSF. Because a catheter is being used, smaller doses can be given in an incremental fashion. Such administration is particularly advantageous in high-risk parturients such as those with cardiac disease, respiratory disease, morbid obesity, and neuromuscular disease. To reduce the risk of headache after this technique, the epidural needle should be turned so that it is parallel to the dural fibers at the time of insertion. In addition, to further reduce the risk of headache, it has been suggested that several steps be taken, including leaving the epidural catheter in situ for more than 12 hours and injecting a bolus of preservative-free normal saline before removal of the catheter. ^[190]