Association of Optic Nerve Sheath Diameter and Postoperative Delirium

December 16, 2025 updated by: Mauricio Giraldo, London Health Sciences Centre Research Institute OR Lawson Research Institute of St. Joseph's

Correlation Between Optic Nerve Sheath Diameter Measured by Ultrasound and Delirium in Cardiac Surgery

Postoperative delirium is a sudden and reversible disturbance of mental function, occurring after surgery, characterized by confusion, inattention, and fluctuating mental status, which can manifest as agitation or lethargy. It is a common post-operative complication, especially in older adults, and is associated with longer hospital stays and worse recovery outcomes. Validated delirium screening tools such as the Intensive Care Delirium Screening Checklist (ICDSC) and the Richmond Agitation and Sedation Scale (RASS) are widely used tools to assess delirium. However, the sensitivity of these screening tools can be variable when used in real-world practice and may miss early cases of delirium. The optic nerve sheath is a protective sheath that encloses part of the optic nerve that is located at the back of the eye. Measurement of the optic nerve sheath diameter is usually done using ultrasound to detect increased cranial pressure. Previous studies that have been conducted have shown that increased ONSD may be associated with occurrence of postoperative delirium. The purpose of this study is to determine if there is an association between optic nerve sheath diameter (ONSD) and the occurrence of delirium after surgery. This study will be conducted at the London Health Sciences Centre and will include 300 patients.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

Delirium is one of the most frequent and serious complications after cardiac surgery, with reported incidence between 15-30% depending on patient population, procedure type, and diagnostic method. It is associated with prolonged ICU and hospital length of stay, increased risk of institutional discharge, higher readmission rates, long-term cognitive impairment, and mortality. Validated delirium screening tools such as the Confusion Assessment Method for the ICU (CAM-ICU) and the Intensive Care Delirium Screening Checklist (ICDSC) are widely used, but their sensitivity in real-world practice can be variable, sometimes missing early cases despite high specificity. This contributes to delayed recognition and potentially worse outcomes.

Ultrasound measurement of the optic nerve sheath diameter (ONSD) has emerged as a non-invasive surrogate marker for intracranial pressure (ICP). Several meta-analyses confirm good diagnostic accuracy of ONSD ultrasound compared to invasive ICP monitoring. Concordance studies also demonstrate strong agreement between ultrasound and MRI ONSD measurements, particularly when standardized measurement protocols are used (e.g., 3 mm posterior to the retina, bilateral averaging). These findings support the reliability of ONSD ultrasound as a bedside monitoring tool.

In critical care, early broadening of ONSD has been associated with delirium, coma, and death within 28 days. Importantly, the first cardiac surgery-specific study that prospectively examined patients undergoing open-heart surgery and found that increased peri-operative ONSD was independently associated with postoperative delirium. Their findings suggest that ONSD may serve not only as a marker of raised ICP but also as a predictive biomarker for delirium in the cardiac surgical population. Taken together, the burden of postoperative delirium in cardiac surgery, the limitations of current screening methods, and the growing evidence supporting ONSD as a surrogate of cerebral dynamics provide the rationale for this study. We hypothesize that perioperative or early ICU ONSD enlargement will be associated with the development of delirium, and that ONSD monitoring may help identify high-risk patients earlier, guiding preventive strategies.

Informed, written consent will be obtained prior to the start of surgery. The participant's surgical plan will not be altered in any way. Participants that are enrolled in this study will have their surgery proceed according to plan and will be placed under general anesthesia using standard of care practices. Cardiopulmonary bypass will be implemented in accordance with standard of care practices.

For the ONSD ultrasound, the ultrasound will be performed using a linear probe 7.5-13 MHz and will follow standard practice for this procedure. Patients will have closed eyelids covered with a Tegaderm adhesive for eye protection. Ultrasound gel will be applied to the patient's eyelids. The ultrasound probe will be gently placed on the patient's eyelids and to locate the optic nerve and measure ONSD. The ultrasound scan will be performed 3 mm posterior to retina with 4 measurements taken at each time point to allow for a mean result to be determined. Average time for each measurement is 1 minute. Each ultrasound will take 10-15 minutes to complete. This ONSD ultrasound will be performed at the following time points:

  1. Prior to the start of surgery
  2. At the start of cardiopulmonary bypass (CPB)
  3. At the end of cardiopulmonary bypass
  4. Admission to the ICU
  5. 1 hour after ICU admission
  6. 6 hours after ICU admission
  7. 24 hours after ICU admission
  8. Daily until hospital discharge for delirious patients or daily until discharge from the ICU for non-delirious patients.

Delirium will be assessed by administering the Intensive Care Delirium Screening Checklist (ICDSC) to patients twice daily until discharge from ICU. This ICDSC will be administered in person. The study team will also collect information such as the patient's age, biological sex, height, weight, medications, medical history, surgical details, results of preoperative and postoperative blood work, pain scores that are collected as part of standard of care practices, and details of their postoperative recovery.

Study Type

Interventional

Enrollment (Estimated)

300

Phase

  • Not Applicable

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

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

Description

Inclusion Criteria:

  • A d u l t s ≥ 1 8 y e a r s .
  • Scheduled for cardiac surgery requiring cardiopulmonary bypass (CPB) (e.g., Coronary artery bypass graft (CABG), valve, combined procedures, aortic surgery).
  • Anticipated postoperative admission to the Cardiac ICU with expected stay >48 hours.
  • Preoperative ability to undergo ocular ultrasound examination (closed-eyelid scanning).
  • Provided informed consent to participate in this study.

Exclusion Criteria:

  • Known or suspected open-globe injury, penetrating ocular trauma, or intraocular foreign body.
  • Recent ocular surgery or intravitreal intervention within the past 6 weeks (if surgeon advises against periocular pressure).
  • Ocular conditions that invalidate ONSD measurement (e.g., severe proptosis, advanced optic neuropathies, orbital tumors) or obstruct ultrasound window (extensive periocular dressings, severe periorbital edema).
  • Known intracranial pathology expected to significantly alter baseline ONSD (e.g., large mass lesion with midline shift, obstructive hydrocephalus) or presence of external ventricular drain at baseline.
  • Severe facial trauma or unstable cervical spine precluding safe positioning for ocular ultrasound.
  • P r e g n a n c y .
  • Inability to perform serial ONSD assessments at scheduled timepoints (e.g., continuous prone positioning) despite reasonable accommodations.
  • Enrollment in a conflicting interventional trial that mandates deviations from delirium assessment or ONSD protocol.
  • Inability to communicate in the English language.

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

  • Primary Purpose: Diagnostic
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Optic nerve sheath diameter (ONSD) ultrasound

Optic nerve sheath diameter (ONSD) ultrasound to be performed at the following time points:

  1. Prior to the start of surgery
  2. At the start of cardiopulmonary bypass (CPB)
  3. At the end of cardiopulmonary bypass
  4. Admission to the ICU
  5. 1 hour after ICU admission
  6. 6 hours after ICU admission
  7. 24 hours after ICU admission
  8. Daily until hospital discharge for delirious patients or daily until discharge from the ICU for non-delirious patients.

Delirium will be assessed by administering the Intensive Care Delirium Screening Checklist (ICDSC) to patients twice daily until discharge from ICU.
Procedure: Optic nerve sheath diameter (ONSD) ultrasound
Optic nerve sheath diameter (ONSD) ultrasound to be performed to measure diameter of the optic nerve sheath. Administration of the Intensive Care Delirium Screening Checklist (ICDSC) twice daily until discharge from the ICU.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Impact of optic nerve sheath diameter on postoperative delirium
Time Frame: Days 1-3 postoperatively
This will be measured by comparing the diameter of the optic nerve sheath to the results of the Intensive Care Delirium Screening Checklist (ICDSC) that will be used to measure delirium in patients. The ICDSC will provide a score of 0-8 for patients. Scores of 4 or higher will be considered to be indicative of postoperative delirium.
Days 1-3 postoperatively

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Impact of optic nerve sheath diameter on hospital length of stay
Time Frame: Days 1-7 postoperatively
This will be measured by noting how long the patient is in hospital following surgery and comparing that to optic nerve sheath diameter.
Days 1-7 postoperatively
Impact of optic nerve sheath diameter on mortality
Time Frame: Days 1-7 postoperatively
This will be measured by noting if a participant has died and comparing that to optic nerve sheath diameter.
Days 1-7 postoperatively
Impact of optic nerve sheath diameter on time spent on a ventilator
Time Frame: Days 1-7 postoperatively
This will be measured by noting how long the patient is required to use a ventilator (if applicable) following surgery and comparing that to optic nerve sheath diameter.
Days 1-7 postoperatively
Impact of optic nerve sheath diameter on the need for re-intubation
Time Frame: Days 1-7 postoperatively
This will be measured by noting if a participant requires re-intubation following surgery and comparing that to optic nerve sheath diameter.
Days 1-7 postoperatively

Collaborators and Investigators

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

Sponsor

London Health Sciences Centre Research Institute OR Lawson Research Institute of St. Joseph's

Investigators

  • Principal Investigator: Mauricio Giraldo, MD, London Health Sciences Centre

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)

February 1, 2026

Primary Completion (Estimated)

December 1, 2027

Study Completion (Estimated)

December 31, 2027

Study Registration Dates

First Submitted

November 17, 2025

First Submitted That Met QC Criteria

November 21, 2025

First Posted (Estimated)

November 25, 2025

Study Record Updates

Last Update Posted (Actual)

December 23, 2025

Last Update Submitted That Met QC Criteria

December 16, 2025

Last Verified

December 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • ONSD & Delirium

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

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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