A comparison of the effect of intrathecal and extradural fentanyl on gastric emptying in laboring women.

We studied gastric emptying, using acetaminophen absorption, in 105 women in labor divided into three equal groups of 35 each, after intrathecal (IT) (25 μg, Group S) or extradural (50 μg, Group E) fentanyl in combination with bupivacaine and compared with a control group (Group C) receiving extradural bupivacaine only. The time to maximal acetaminophen concentration (tCa max ), maximal acetaminophen concentration (Ca max ), and areas under the acetaminophen concentration-time curve at 90 and 120 min (AUC 90 and AUC 120 , respectively) were determined. Median (range) tCa max values were 120 (15-180), 82.5 (15-180), and 90 (15-180) min in Groups S, E, and C, respectively (P < 0.05). Mean ± SD Ca max was 13.4 ± 8.82, 17.9 ± 8.06, and 15.0 ± 6.22 μg/mL in Groups S, E, and C, respectively (P < 0.05). Mean ± SD AUC 90 ) and AUC 120 were also significantly smaller in Group S than in the other two groups (430 ± 616, 736 ± 504, and 672 ± 453; and 649 ± 592, 1063 ± 627, and 1053 ± 616 μg. mL -1 . min -1 in Groups S, E, and C, respectively). We conclude that the administration of fentanyl 25 μg IT delays gastric emptying in labor compared with both extradural fentanyl 50 μg with bupivacaine and extradural bupivacaine alone. Implications: We examined emptying of the stomach in women in labor after administration of analgesics by the spinal or the epidural route. We observed that the analgesic, fentanyl, administered by the spinal route, although relieving pain rapidly, may delay emptying of the stomach. In theory, delayed gastric emptying may increase the chance of vomiting and aspiration of gastric contents.