Epidural Saline and Combined Epidural-Spinal Anesthesia

Abstract

To the Editor: We read with interest the article by Takiguchi et al. [1], in which they attributed the mechanism of more cephalad achievement of sensory analgesia from intrathecally injected local anesthetic solution to the "volume effect" of epidurally administered physiological saline. Although they have elegantly demonstrated, for the first time in the literature, the effects of epidural space expansion by saline on the cephalad spread of intrathecally injected contrast medium, their conclusion seems seriously confounded by the following three factors. First, the local anesthetic solution used in the surgical patients (0.3% dibucaine) and the contrast medium used in the volunteers were considerably different with respect to the volume (2.5-3 vs 7 mL) and specific gravity (1.035-1.039 vs 1.268-1.296), respectively. In addition, the surgical patients were resting supine, whereas the volunteers were recumbent, in a with 45[degree sign] head-up position. These factors are likely to affect the cephalad migration of intrathecally administered solutions. Second, the difference in analgesic levels between the control and saline groups in their surgical patients may simply be due to the additive effect of hypalgesia produced by epidurally administered saline [2]. Unless another group, i.e., patients receiving nothing intrathecally after dural puncture but saline epidurally, had been added and spatial and temporal analgesic spread verified, hypalgesic effect of epidural saline cannot be ruled out. Third, the time from intrathecally injected contrast medium to epidurally injected saline is not clear from the article. Unless control patients, i.e., patients receiving intrathecal contrast medium but nothing epidurally, are studied, cephalad spread of the contrast medium cannot be solely attributed to the volume effect of epidural saline. Makoto Tanaka, MD Toshiaki Nishikawa, MD Department of Anesthesia; Akita University, School of Medicine; Akita 010, Japan