RESUMEN
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 (SpO2) <95%. Secondary outcomes included: AUC per hour at SpO2<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 (SpO2<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 SpO2<95% up to 48 hours after surgery. TRIAL REGISTRATION NUMBER: ChiCTR2100054317.