Evaluating the Efficacy and Utility of the Automated Pupillometer in Pain Assessment and Opioid Administration Guidance During the Perioperative Period: A Randomized Controlled Trial

Effective intraoperative and postoperative pain management is critical for patient comfort and recovery, yet traditional methods for assessing pain under general anaesthesia are limited by their subjective nature and reliance on vital signs. Automated pupillometry, which gives the parameters of the pupillary light reflex (PLR) components, offers an objective and quantitative approach to evaluating nociception and pain.

This study aims to evaluate the effectiveness of the automated pupillometry in enhancing early postoperative pain control and to assess its utility in guiding opioid administration during the perioperative period.

A prospective, non-blinded randomized controlled trial will be conducted with 68 patients undergoing laparotomy for gastrointestinal surgery. Participants will be randomly assigned to either an interventional group, where analgesia is guided by automated pupillometry measurements, or a control group receiving standard pain management. Key outcomes include the time to first rescue analgesia, self-reported pain scores, opioid consumption. The automated pupillometry measurements will be taken at key surgical moments, including before induction, pre-incision, and during recovery.

Pain scores and rescue analgesia use will be compared between groups using appropriate statistical tests, and Kaplan-Meier survival curves will analyze time to first rescue analgesia. Regression analyses will explore the relationship between pupillometry readings and postoperative pain.

It is anticipated that the automated pupillometry guided group will experience longer intervals before requiring rescue analgesia and report lower pain scores, suggesting improved pain management and reduced opioid use.

This study could validate automated pupillometry as an innovative tool for optimizing postoperative pain management, potentially improving patient outcomes by enabling more precise and effective analgesia in surgical settings.

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Key information

Conditions

Postoperative Pain Neurologic Manifestations Pain Pain, Postoperative Pathologic Processes Pathological Conditions, Signs and Symptoms Postoperative Complications Postoperative Pain Management Signs and Symptoms

Age range

18 year–70 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Universiti Malaya Medical Centre

Kuala Lumpur, 59100, Malaysia

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

1. Patients aged 18 - 70 years old scheduled for elective/emergency laparotomy with clear awareness and good communication
2. ASA (American Society of Anaesthesiologists) physical status I-III
3. Expected to have moderate to severe pain in the early postoperative period

Exclusion criteria

1. Patient with known pupillary abnormality (such as anisocoria, pharmacologic dilation, previous intraocular surgery)
2. Pre-existing neurological disorder affecting pupillary reflexes
3. Patients on chronic opioid therapy or with a history of substance abuse
4. Non-consenting patients or those with cognitive impairments affecting informed consent

Treatment and study plan

Opioid Analgesic

Drug

Participants in the interventional group will receive an initial dose of 100 mcg IV fentanyl during induction. Remifentanil will be administered via effect-site target-controlled infusion (TCI), with a concentration effect (Ce) ranging from 2 to 8 ng/ml. TCI remifentanil is increased by 0.5 ng/ml if pupillary diameter changes > 20% of the baseline after induction. The automated pupillometry measurement is repeated 5 mins after increment. Prior to skin closing, IV morphine 0.1 mg/kg during skin closing and automated pupillometry measurement is repeated to aim pupillary diameter is within 20% of baseline. Analgesics is titrated according to the anaesthetist's discretion and reason is documented if it is deviated from the protocol.

automated pupillometry

Device

For both arms, automated pupillometry will be measured before induction , after induction(baseline), before the surgical incision, after surgical incision, during skin closure, at PACU 10 mins and at PACU 30 mins.

For intervention arm only, the additional automated pupillometry measurement will be performed after administration of analgesia.

Primary outcomes

post operative opioid consumption

Time frame: first 24 hours post operatively

the amount of post operative opioid consumption including rescue analgesia and patient controlled analgesia morphine usage would be recorded

Secondary outcomes

The correlation between pupillary response metrics (% change, constriction velocity, dilatation velocity, NPi) and opioid dosage administered.

Time frame: automated pupillometry measurements will be done before induction, after induction, before skin incision, during skin incision, after skin incision, during skin closure, and at post anaesthesia recovery unit 10 min and 30 min.

To find the measurement changes or correlation with opioiod administration, and to analyse it statistically

Sponsors and collaborators

Lead sponsor

University of Malaya

Other

Registry information

Important dates

Study start: 2026
Primary completion: 2026
Study completion: 2027
First posted: May 29, 2026
Registry last updated: May 29, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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