Letters to the Editor
Hebl et al. (1) found that the success rate of epidural analgesia and anesthesia in patients who have undergone dural puncture to be similar to that of patients who have undergone two previous epidural anesthetics. Those findings were different from an earlier report by Ong et al. (2), in which epidural analgesia was often impaired after dural puncture with and without subsequent blood patch. The contrary results may be explained by differences in patient groups and technical differences in identifying the epidural space.
The patients of Ong et al. (2) were all parturients who had dural puncture with 16-gauge Tuohy needles. Seventy-one of the 87 patients for Hebl et al. (1) had dural puncture for spinal anesthesia. The spinal anesthesia was probably performed with finer needles.
The mean ages of patients of Ong et al. (2) ranged from 22 to 27 years, whereas the mean ages of patients of Hebl et al. (1) ranged from 34 to 40 years.
The most common technique for identification of the epidural space for Ong et al. (2) was by loss of resistance to air. Hebl et al. (1) used the saline loss of resistance technique.
Further studies controlling the variations in the study patients and the loss of resistance techniques for identification of epidural space may explain the different observations in the two studies.
Bill Ong 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.