Different doses of epidural morphine combined with multimodal analgesia strategies for postpartum pain management: study protocol for a single-centre, double-blind randomised, pragmatic clinical trial.

Abstract

The neuraxial morphine has been regarded as the gold standard for postpartum analgesia. However, the recent advancements in patient-controlled analgesia and various regional nerve blocks have led to the implementation of multimodal analgesia strategies, which aim to reduce opioid usage and associated complications while ensuring satisfactory pain relief. The objective of this research is to investigate the optimal dosage of epidural morphine for alleviating moderate and severe pain after caesarean sections in healthy parturients, as well as reducing unnecessary burden of respiratory monitoring resources. The present single-centre randomised controlled pragmatic clinical trial aims to enrol a total of 310 healthy parturients with American Society of Anesthesiologists grade I/II, who are scheduled for caesarean section under combined spinal and epidural anaesthesia at West China Second University Hospital of Sichuan University. The recruitment process has not yet commenced and is anticipated to commence in March 2024, concluding in September 2024. Enrolled patients will be evenly distributed into five groups, namely morphine groups (M1-M4) and the control group (M0). The primary outcome measure is the incidence rate of postoperative use Numerical Rating Scale (NRS) pain score ≥4 points within 24 hours, which will be primarily assessed through bedside follow-up conducted by investigators and patient self-assessment at 2, 4, 6, 8, 12 and 24 hours postoperatively. The secondary outcomes encompass the following: incidence of postoperative NRS score ≥4 within 48 hours, occurrence of SpO2 <90% (during air inhalation)/ SpO2 <95% (during nasal cannula oxygen inhalation) and respiratory rate (RR)＜10 breaths/min recorded on the bedside monitoring, Ramsay sedation score, administration of rescue analgesics and total usage of patient-controlled intravenous analgesia pump, time to first flatus and food intake, maternal and neonatal urinary morphine concentrations, and any other maternal adverse reactions such as nausea, vomiting, pruritus, urinary retention and neonatal depression. The administration of local anaesthetics, surgical procedures and the timing for administering rescue analgesics will not be subject to any restrictions. Ethical approval has been obtained from the Ethics Committee of West China Second University Hospital, Sichuan University (2022(269)). ChiCTR2400080350.