3The extent of the CSF volume reduction induced by epidural saline, however, is unclear. 1Epidural saline injection compresses the dural sac. 1–9The volume effect occurs when the volume of the fluid injected into the epidural space compresses the dural sac, squeezes the cerebrospinal fluid (CSF) compartment, and displaces the CSF cephalad, thus raising the cephalad spread of spinal drugs. 2–9Although the exact mechanism by which an epidural “top-up” reinforces anesthesia in CSE is not fully understood, this mechanism can be explained partly by the effect of the local anesthetic and partly by an epidural volume effect. 1Injecting local anesthetic or saline into the epidural space after spinal anesthesia speeds the onset, increases the sensory block level, or both.
(2) The maximum reduction of the sum of the total of seven disk areas occurred 5 min after epidural saline injection thereafter, dural compression was gradually restored but did not return to the value before injection for 30 min.ĬOMBINED spinal–epidural anesthesia (CSE) allows for a rapid onset of neuraxial blockade, which can be subsequently modified. However, there was no significant relation between measures of CSF velocity waveform and dural area in any patient.
After the saline injection, the synchronization between the CSF velocity waveform and the cardiac cycle disappeared in significantly more patients in the 10-ml group (7 of 9 patients) than in the other groups (P < 0.05). There were significant differences among the three groups (P < 0.05 approximately 0.001). The mean reductions in CSF volume were 2.0 +/- 1.0 ml in the 5-ml group, 4.4 +/- 1.4 in the 10-ml group, and 7.2 +/- 2.6 in the 15-ml group. (1) Saline injected through the epidural catheter compressed the dural sac with variability of the extent of compression, resulting in a significantly decreased CSF volume in all patients (P <= 0.001).
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