Letters to the Editor
We would like to thank Dr. Ong for his interest in our recent article addressing subsequent epidural anesthesia and analgesia in patients who have a history of dural puncture, with or without epidural blood patch (1). In his letter to the editor, Dr. Ong suggested that differences in patient age, needle size during dural puncture, and technique of epidural needle placement (air versus saline loss of resistance) may account for the significant difference in epidural success rates reported in our investigation (95%) compared with those of Ong et al. (65%) (2). Although differences in needle size (during dural puncture) and age existed between the two studies, a review of the current literature provides no evidence that these variables contribute to epidural success rates. An additional study by Blanche et al. (3) had similar results as ours, namely that previous dural puncture did not affect the efficacy of subsequent epidural analgesia. They reported a subsequent epidural success rate of 91% in parturients whose age and size of dural puncture were similar to those of Ong et al. (2).
Finally, Dr. Ong has suggested that their loss of resistance technique with air (as compared with saline in our parturients) may have contributed to their lower subsequent epidural success rates. Although this may explain subsequent epidural failure in patients who have undergone recent (within days) epidural needle placement with air (4), it seems unlikely that this would have any long-term implications. Currently, there is no evidence that suggests epidural needle placement with small volumes of air has any significance on subsequent epidural efficacy several months or years later.
Therefore, it is improbable that the differences in subsequent epidural success rates can be attributed to needle size, age, or technique. As a result, we conclude that previous dural puncture, with or without epidural blood patch, does not affect the success rate of subsequent epidural anesthesia or analgesia.
James R. Hebl
MD Terese T. Horlocker
MD Robert C. Chantigian MD
1. Hebl JR, Horlocker TT, Chantigian RC, Schroeder DR. Epidural anesthesia and analgesia are not impaired after dural puncture with or without epidural blood patch. Anesth Analg 1999; 89:390–4.
2. Ong BY, Graham CR, Ringaert KR, et al. Impaired epidural analgesia after dural puncture with and without subsequent blood patch. Anesth Analg 1990; 70:76–9.
3. Blanche R, Eisenach JC, Tuttle R, Dewan DM. Previous wet tap does not reduce success rate of labor epidural analgesia. Anesth Analg 1994; 79:291–4.
4. Dalens B, Bazin J, Haberer J. Epidural bubbles as a cause of incomplete analgesia during epidural anesthesia. Anesth Analg 1987; 66:679–83.