Background: Children undergoing selective dorsal rhizotomy (SDR) experience severe pain postoperatively; a pain related to both the extensive surgical exposure with multilevel laminectomy and nerve root manipulation. We sought to define an optimal dose of continuous intrathecal (IT) morphine and bupivacaine to treat this severe pain. The aim of this study was to compare two different concentrations of morphine in a fixed dose of bupivacaine with regard to the analgesic effect and survey if they differed in side effects.
Methods: Twenty-six children, aged 2.7–7.4 years undergoing SDR were included in this study. Postoperatively 11 children received a continuous infusion of morphine 0.4 μg.kg−1.h−1 and bupivacaine 40 μg.kg−1.h−1 (low-dose group) and 15, a continuous infusion of morphine 0.6 μg.kg−1.h−1 and bupivacaine 40 μg.kg−1.h−1 (high-dose group). The Behavioral Observational Pain Scale (BOPS) was used to evaluate pain.
Results: Better pain relief was obtained in the high-dose group seen in lower BOPS score compared with the low-dose group [P = 0.03, Fisher's permutation test and P = 0.06 Wilcoxon–Mann–Whitney (WMW) test]. The low-dose group received seven times as much ketobemidone 0.43 ± 0.54 mg.kg−1 48 h−1 compared with 0.06 ± 0.09 mg.kg−1 48 h−1 in the high-dose group (P = 0.0005 Fisher's permutation test, P = 0.0017 WMW test). There was no statistical difference in pruritus and postoperative nausea and vomiting between the groups. Respiratory and hemodynamic depression was not found.
Conclusion: This study shows that, compared with low-dose, the higher dose of continuous IT morphine combined with bupivacaine, significantly reduce pain score and postoperative intravenous analgesic requirements without increasing adverse effects.