Effects of hydromorphone-based patient-controlled intravenous analgesia on postoperative hypoxaemia: a randomised controlled non-inferiority clinical trial

Objective This study aimed to compare the effects of patient-controlled intravenous analgesia (PCIA) with and without low-basal infusion on postoperative hypoxaemia. Design A randomised parallel-group non-inferiority trial. Setting The trial was conducted at a grade-A tertiary hospital from December 2021 to August 2022. Participants 160 adults undergoing gastrointestinal tumour surgery and receiving postoperative PCIA. Interventions Participants randomly received a low-basal (0.1 mg/hour of hydromorphone) or no-basal infusion PCIA for postoperative 48 hours. Primary and secondary outcome measures Primary outcome was area under curve (AUC) per hour for hypoxaemia, defined as pulse oxygen saturation (SpO(2)) <95%. Secondary outcomes included: AUC per hour at SpO(2)<90% and <85%, hydromorphone consumption, ambulation time and analgesic outcomes up to 48 hours after surgery. Results Among 160 randomised patients, 159 completed the trial. An intention-to- treat analysis showed that AUC per hour (SpO(2)<95%) was greater in the low-basal infusion group compared with the no-basal infusion group, with a median difference of 0.097 ( 95% CI 0.001 to 0.245). Non-inferiority (margin: ratio of means (ROM) of 1.25) was not confirmed since the ROM between the two groups was 2.146 (95% CI 2.138 to 2.155). Hydromorphone consumption was higher in the low-basal group than in the no-basal group (median: 5.2 mg versus 1.6 mg, p<0.001). Meanwhile, there were no differences in the AUC values at the other two hypoxaemia thresholds, in ambulation time, or pain scores between the groups. Conclusions Among the patients receiving hydromorphone PCIA after gastrointestinal tumour resection, low-basal infusion was inferior to no-basal infusion PCIA for postoperative hypoxaemia at SpO(2)<95% up to 48 hours after surgery. Trial registration number ChiCTR2100054317.