We evaluated the effect of 1, 20, and 40 mL of epidural saline flush on recovery from lidocaine epidural anesthesia. Eight volunteers were studied for three study periods, each separated by 72 h. The volume of saline was randomized, and a new catheter was inserted for each study period. A standardized dose of 20 mL of 2% plain lidocaine was injected for 10 min, followed by an epidural saline flush 30 min later. Sensory block was assessed by pinprick and transcutaneous electrical stimulation and motor block by a modified Bromage scale and isometric maximal force contraction. Times to void and ambulate independently before discharge were recorded. Peak plasma lidocaine concentrations and time to peak concentration were determined. Results from six volunteers showed that epidural saline, 40 mL, significantly altered anesthetic resolution, accelerating the time of complete sensory and motor block regression (P < 0.05). Median peak levels of sensory and motor block and times to void and ambulate were similar among treatment groups. Peak plasma lidocaine concentrations were similar in all treatment groups. Our data suggest that a 40-mL epidural saline injection 30 min after the induction facilitates regression of epidural lidocaine anesthesia, but a 20-mL bolus does not. Epidural saline injection does not affect vascular absorption of epidural lidocaine.
Implications: Epidural catheter flushing with 40 mL of saline, after establishment of epidural lidocaine anesthesia, can facilitate sensory and motor block recovery. However, this does not affect vascular absorption of epidural lidocaine.