A Predictive Model for Postoperative Analgesic Requirements After Abdominal Surgery

September 1, 2026 updated by: Chaw Sook Hui

Quantitative Analysis of Postoperative Analgesia Following Abdominal Surgery Using Repeated Time-to-Event Modelling of Rescue Analgesic Administration

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.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

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.

Study Type

Observational

Enrollment (Estimated)

65

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

  • Name: Tsyr Xiang Teoh, Master of Anaesthesiology
  • Phone Number: +603-79494422
  • Email: teohtx@um.edu.my

Study Locations

  • Malaysia
      • Kuala Lumpur, Malaysia, 59100
        • Universiti Malaya Medical Centre
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

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.

Description

Inclusion Criteria:

  • Adult patients aged 18-75 years
  • American Society of Anesthesiologists (ASA) physical status I-III
  • Elective open or laparoscopic abdominal surgery under general anaesthesia
  • Expected postoperative ward or high-dependency unit (HDU) stay of ≥ 48 hours
  • Ability to provide written informed consent in Bahasa Malaysia or English
  • Ability to comprehend and self-report pain using the Numerical Rating Scale (NRS, 0-10)

Exclusion Criteria:

  • Chronic opioid therapy, defined as regular opioid use for ≥ 4 weeks prior to surgery
  • Severe hepatic impairment (Child-Pugh Class B or C) or severe renal impairment (eGFR < 30 mL/min/1.73 m²)
  • Known allergy or hypersensitivity to morphine or any opioid analgesic
  • Cognitive impairment (documented diagnosis of dementia or delirium), language barrier, or communication deficit precluding reliable NRS self-report
  • Documented history of substance use disorder (including opioid use disorder)
  • Withdrawal of informed consent at any point

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Adult Patients Undergoing Elective Abdominal Surgery
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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Rescue Analgesic Administration Events During the First 48 Hours After Abdominal Surgery
Time Frame: Up to 48 hours after completion of 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.
Up to 48 hours after completion of surgery

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Postoperative Pain Scores
Time Frame: At PACU arrival/ every 15 minutes during PACU stay/ every 4 hours up to 48 hours after surgery
Pain intensity measured using the Numerical Rating Scale (NRS; 0-10) at predefined postoperative time points, including before and after rescue analgesic administration.
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
Time Frame: Up to 48 hours after completion of surgery
Relationship between predicted morphine plasma concentration derived from individual dosing histories and the hazard of subsequent rescue analgesic administration.
Up to 48 hours after completion of surgery

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Chaw Sook Hui

Collaborators

University of Malaya

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

January 1, 2027

Primary Completion (Estimated)

July 1, 2027

Study Completion (Estimated)

June 1, 2028

Study Registration Dates

First Submitted

July 25, 2026

First Submitted That Met QC Criteria

September 1, 2026

First Posted (Actual)

September 3, 2026

Study Record Updates

Last Update Posted (Actual)

September 3, 2026

Last Update Submitted That Met QC Criteria

September 1, 2026

Last Verified

September 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 2026223-16373
  • NMRR ID-26-02772-RUY (Registry Identifier: NMRR)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

IPD Plan Description

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.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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