The Safety of Continuous Spinal Anesthesia

In Response: The letter by Dr. Standl is of special interest because it supports the ongoing use of continuous spinal anesthesia using a 28-gauge microcatheter. The introduction of microcatheters in 1989 allowed the advantages of continuous spinal anesthesia to be extended to younger patients without the associated high frequency of post-dural puncture headache (PDPH). However, many of the touted advantages of continuous spinal anesthesia were not present with a microcatheter technique. There were frequent technical problems, including catheter kinking and breakage (resulting in retained intrathecal fragments) [1]. The frequency of PDPH was as high as 40% in partutients, a population targeted for microcatheter techniques [2,3]. Consequently, many anesthesiologists reserved microcatheter placement primarily for elderly patients [4,5], with a debatable reduction in PDPH compared with a macrocatheter technique [3,5]. Finally, a total of 14 cases of cauda equina syndrome occurring over a 30-mo period (compared with only 1 associated with the use of a macrocatheter in the previous 5 yr) led to the recall of all catheters 27-gauge or smaller in May 1992. Dr. Standl states that he has uneventfully inserted more than 1200 28-gauge microcatheters in orthopedic or trauma patients, regardless of patient age or gender. We applaud his safety record and encourage him to report his results in a peer-reviewed journal. However, with the current published information, it is difficult to justify the use of continuous spinal anesthesia in all patients, given the number of alternative regional anesthetic techniques available and the technical problems, frequency of PDPH, and risk of neurologic complications associated with the microcatheter technique. In addition, the lack of definite benefits of microcatheters compared with macrocatheters makes a continuous microcatheter technique even less appropriate for general use. A large prospective study is needed to determine variables associated with the safe use of microcatheters. Until then, we recommend that continuous spinal anesthesia be performed after a risk/benefit assessment and comparison with other regional anesthetic techniques. Terese T. Horlocker, MD Department of Anesthesiology; Mayo Clinic; Rochester, MN 55905