Does Combined Spinal-Epidural Analgesia Alter the Incidence of Paresthesia During Epidural Catheter Placement?

Abstract

To the Editor: Combined spinal-epidural analgesia (CSE) is becoming an increasingly popular method for obtaining labor analgesia. It allows for the rapid onset of spinal analgesia while an epidural catheter is placed. Because the epidural catheter in CSE is placed after the induction of spinal analgesia, there is some concern that patients may not feel paresthesias and, consequently, may be more prone to neurologic injury if catheters are advanced or injected. Indeed, the injection of anesthetic through an epidural catheter in the setting of a persistent paresthesia has previously been linked to severe neurologic injury [1]. Although complication rates for CSE compared with epidural anesthesia with regard to dural puncture, hypotension, pruritus, nausea, and vomiting have been previously reviewed [2], the incidence of paresthesia with placement of the epidural catheter during CSE has not been examined. To test the hypothesis that a patient's ability to sense paresthesias is reduced when an epidural catheter is placed after the induction of spinal analgesia, we retrospectively analyzed data collected on 4202 patients requesting labor analgesia at Brigham and Women's hospital during 1994. After formal approval of our hospital's review board, we randomly selected six 1-mo blocks. We analyzed the records of all patients receiving epidural analgesia (n = 3910) or CSE (n = 292) for the occurrence of paresthesia during placement of the epidural catheter. Blocks were placed by residents and fellows with attending supervision using our usual technique, loss of resistance to air with a Weiss needle. Power analysis suggested a greater than 80% likelihood of detecting a 10% difference in the incidence of paresthesia at alpha = 0.05. We found no significant difference in the incidence of paresthesia between the group: 30.7% in the epidural group and 32.2% in the CSE group (chi squared, P = 0.59). Although the retrospective design of this analysis does not guarantee that the anesthetics or the anesthesiologists performing them were comparable in all respects, we believe that any difference in paresthesia risk between epidural and CSE techniques is likely to be minimal. Because the process of threading an epidural catheter during a CSE is identical to the process of threading an epidural catheter in the absence of spinal anesthesia, our reported 30% incidence of paresthesia probably represents the true incidence of paresthesias in both groups. The incidence of paresthesia seen in this study agrees with previously reported rates of paresthesia with epidural catheter placement, ranging from 20% to 44% [3-5]. Our results only apply to CSE performed for labor analgesia in which sensory blockade is limited. CSE performed with subarachnoid local anesthetic sufficient to produce surgical anesthesia may induce sensory blockade profound enough the limit patients' ability to accurately report paresthesias when an epidural catheter is placed. Similar concerns have been raised regarding placement of an epidural catheter cephalad to the termination of the spinal cord in anesthetized patients [6]. In conclusion, placing an epidural catheter immediately following induction of spinal analgesia for labor as part of CSE does not alter the incidence of paresthesia. Aaron Levin, MD Scott Segal, MD Sanjay Datta, MD Department of Anesthesia; Brigham and Women's Hospital; Harvard Medical School; Boston, MA 02115