Alteration of renal blood flow during epidural anesthesia in normal subjects

The cardiovascular consequences of epidural anesthesia secondary to sympathetic blockade are well documented; however, their repercussions on renal hemodynamics in humans have not been reported. We investigated the effect of epidural anesthesia on renal blood flow (RBF) in 13 healthy volunteers 18-45 yr of age. RBF was measured using paraaminohippurate clearance before and after bilateral T6 epidural sensory block (to ensure adequate sympathetic renal nerve blockade). Epidural anesthesia was established using 22 +/- 3 mL of 2% plain lidocaine (without epinephrine) via L1-L2 epidural catheter; urine output was measured using a three-way Foley catheter. Mean arterial pressure remained > or = 70 mm Hg in all subjects without any pharmacologic intervention. Mean RBF before epidural anesthesia was 16.1 +/- 6.8 mL.kg-1.min-1 and 14.3 +/- 2.9 mL.kg-1.min-1 after bilateral T6 epidural blockade. We conclude that the institution of epidural anesthesia in healthy subjects does not result in a significant change in RBF (P > 0.25).