Systemic vascular uptake of epinephrine from the lumbar epidural space in parturients

To assess the systemic vascular uptake of epinephrine from the lumbar epidural space in parturients during epidural anesthesia for cesarean delivery.

Thirty-eight healthy patients were randomly divided into two equal groups. In one group, bupivacaine-epinephrine (5 micrograms/mL) mixture was used to produce lumbar epidural anesthesia to a T6 level; in the other group, bupivacaine 0.5%. Maternal venous plasma epinephrine and norepinephrine concentrations were measured before anesthesia (baseline), at a T6 sensory level and at delivery; and 10, 20, 30, and 50 minutes after delivery. Statistical comparisons were made using nonparametric analysis of variance at P < .05.

In the bupivacaine-epinephrine group, the plasma epinephrine concentration increased approximately fourfold at T6 sensory level compared to the baseline value or to the corresponding value in the bupivacaine group (P < .01), and it remained elevated significantly for 20 minutes after delivery. In the bupivacaine group, no significant changes occurred in the epinephrine concentrations. In both groups, plasma norepinephrine concentration increased at T6 level approximately 1.8-fold compared to the baseline value (P < .01), with no intergroup differences.

Epinephrine is absorbed from the epidural space and raises the maternal circulating epinephrine concentration. Maternal plasma norepinephrine concentration rises during lumbar epidural anesthesia regardless of epinephrine use.