Iliohypogastric-ilioinguinal peripheral nerve block for post-Cesarean delivery analgesia decreases morphine use but not opioid-related side effects.

Abstract

To examine if ilioinguinal-iliohypogastric nerve block could reduce the need for post-Cesarean delivery morphine analgesia and thus reduce the incidence of opioid related adverse-effects. A multi-level technique for performing the nerve block with bupivacaine was developed and then utilized in this two-part study. Part one was a retrospective assessment of Cesarean delivery patients with and without ilioinguinal-iliohypogastric blocks to determine if the technique reduced patient controlled analgesia morphine use and thus would warrant further study. The second phase was a randomized double-blind placebo-controlled trial to compare post-Cesarean morphine use and the appearance of opioid-related side effects between the anesthetic and placebo-injected groups. Both phases demonstrated that our method of ilioinguinal-iliohypogastric nerve block significantly reduced the amount of iv morphine used by patients during the 24 hr following Cesarean delivery. In the retrospective assessment, morphine use was 49 +/- 30 mg in the block group vs 79 +/- 25 mg in the no block group (P = 0.0063). For the prospective trial, patients who received nerve blocks with bupivacaine had a similar result, self-administering 48 +/- 27 mg of morphine over 24 hr compared to 67 +/- 28 mg administered by patients who received infiltrations of saline. However, despite the significant decrease in morphine use, there was no reduction in opioid-related adverse effects: the incidences of nausea were 41% and 46% (P = 0.70) and for itching were 79% and 63% (P = 0.25) in the placebo and nerve block groups, respectively. A multi-level ilioinguinal-iliohypogastric nerve block technique can reduce the amount of systemic morphine required to control post-Cesarean delivery pain but this reduction was not associated with a reduction of opioid related adverse effects in our study group.