An observational study in Postoperative Pain, Postoperative Analgesia and Opioid Analgesic Requirement, sponsored by Chaw Sook Hui. Not yet recruiting at 1 site in Malaysia. Open to participants aged 18 Years to 75 Years. Per ClinicalTrials.gov, last updated 2026-09-03.
Sponsored by Chaw Sook Hui · Observational
Postoperative pain remains a common challenge after abdominal surgery despite the use of standard multimodal pain management strategies. Poorly controlled pain can delay recovery, limit early mobilisation, reduce patient comfort, and increase the risk of longer-term pain problems.
This study aims to develop a predictive model to better understand and anticipate patients' postoperative pain relief needs after abdominal surgery. The study will observe adults undergoing elective abdominal surgery and collect information on their pain scores, pain medication use, surgical characteristics, and recovery during the first 48 hours after surgery.
Participants will receive standard postoperative pain management according to usual clinical practice. The study will analyse patterns of rescue pain medication use, including when and how often additional pain relief is required after surgery. The collected information will be used to develop a model that can predict factors associated with increased pain medication requirements.
The goal of this research is to improve understanding of individual differences in postoperative pain and provide a foundation for more personalised pain management strategies in the future. The findings may help healthcare providers identify patients who are more likely to require additional pain relief and support the development of safer and more effective approaches to postoperative pain control.
Postoperative pain remains a significant clinical challenge following abdominal surgery. Although multimodal analgesic strategies are widely implemented, many patients continue to experience moderate-to-severe pain during the early postoperative period and require repeated rescue analgesic administration. Current approaches to evaluate postoperative analgesic requirements often rely on total opioid consumption or time to first rescue analgesia. However, these methods may not fully capture the dynamic and repeated nature of postoperative pain and analgesic demand.
This study aims to develop a predictive model to characterise postoperative analgesic requirements in adults undergoing elective abdominal surgery. The study will use repeated time-to-event pharmacokinetic-pharmacodynamic modelling to analyse the timing and pattern of rescue morphine administration during the first 48 hours after surgery.
This is a prospective observational cohort study involving adult patients undergoing elective open or laparoscopic abdominal surgery under general anaesthesia. Participants will receive standard postoperative analgesic management according to routine clinical practice. No changes to clinical care will be introduced as part of the study.
Data collected will include patient demographics, surgical characteristics, anaesthetic details, postoperative pain scores, and analgesic administration records. Rescue analgesic events will be captured from patient-controlled analgesia (PCA) device records, including the timing and dose of successful morphine administrations. Individual morphine exposure will be estimated using documented dosing histories and published population pharmacokinetic parameters.
The collected data will be analysed using repeated time-to-event pharmacokinetic-pharmacodynamic modelling. The model will evaluate factors influencing the likelihood of requiring rescue analgesia over time, including temporal patterns, circadian effects, morphine exposure, and patient or surgical characteristics. Model performance will be assessed using simulation-based evaluation methods, including predictive checks and bootstrap analysis.
The expected outcome of this study is the development of a validated predictive framework for postoperative analgesic requirements after abdominal surgery. This model may provide a foundation for future personalised analgesic strategies, allowing earlier identification of patients at higher risk of inadequate pain control and supporting safer, more effective postoperative pain management.
Adults undergoing elective abdominal surgery under general anaesthesia will be enrolled in this prospective observational cohort study. The study population represents patients experiencing the early postoperative recovery phase, where pain trajectories and analgesic requirements vary substantially between individuals. Participants will be observed during the first 48 hours after surgery to characterise patterns of rescue analgesic use and postoperative pain.
The study aims to develop a predictive model of postoperative analgesic requirements by integrating analgesic administration patterns with patient and surgical characteristics. The findings will support a better understanding of individual variability in postoperative pain management and provide a foundation for future personalised analgesic strategies.
Exclusion Criteria:
Adult patients aged 18-75 years undergoing elective open or laparoscopic abdominal surgery under general anaesthesia will be enrolled in this prospective observational cohort. Participants will receive standard postoperative analgesic management according to routine clinical practice. Rescue analgesia will be provided using intravenous morphine via patient-controlled analgesia (PCA), and the timing and dose of successful analgesic administrations will be recorded during the first 48 hours after surgery. Patient demographics, surgical characteristics, pain scores, and analgesic administration data will be collected to develop a predictive model of postoperative analgesic requirements.
Drug: Intravenous Morphine Patient-Controlled Analgesia
Participants will receive intravenous morphine via patient-controlled analgesia (PCA) as part of standard postoperative analgesic management following elective abdominal surgery. The study does not assign or modify analgesic treatment. Morphine PCA usage, including timing and dose of successful administrations, will be recorded to characterise postoperative analgesic requirements using repeated time-to-event modelling.
Rescue Analgesic Administration Events During the First 48 Hours After Abdominal Surgery
The number and timing of successful rescue analgesic events following elective abdominal surgery. A rescue analgesic event is defined as each successful patient-controlled analgesia (PCA) activation resulting in intravenous morphine delivery. The repeated occurrence and timing of rescue analgesic events will be analysed using repeated time-to-event modelling to characterise postoperative analgesic requirements.
Time frame: Up to 48 hours after completion of surgery
Postoperative Pain Scores
Pain intensity measured using the Numerical Rating Scale (NRS; 0-10) at predefined postoperative time points, including before and after rescue analgesic administration.
Time frame: At PACU arrival/ every 15 minutes during PACU stay/ every 4 hours up to 48 hours after surgery
Morphine Exposure and Relationship With Rescue Analgesic Hazard
Relationship between predicted morphine plasma concentration derived from individual dosing histories and the hazard of subsequent rescue analgesic administration.
Time frame: Up to 48 hours after completion of surgery
Documents are hosted by the registry — open the source record to download them.
Plan to share: Undecided — A formal plan for sharing individual participant data has not yet been established. Any future data sharing will be considered after completion of the study, publication of the primary findings, and approval by the relevant institutional ethics committee. If data sharing is undertaken, only de-identified data will be considered, and access will be subject to appropriate data protection measures and institutional requirements.
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