Impact of Intraoperative Oxygenation Practices on Patient Outcomes (IntraOp Ox)

This multicenter, cluster-randomized, cluster-crossover clinical trial evaluates the impact of three intraoperative FiO2 (Fraction of Inspired Oxygen) oxygenation strategies-lower (FiO₂ 0.21-0.40), intermediate (FiO₂ 0.40-0.80), and higher (FiO₂ 0.80-1.00)-on postoperative organ injury and mortality in adult surgical patients. The trial aims to determine the optimal oxygenation strategy to improve perioperative outcomes.

Study Overview

• Status: Recruiting
• Conditions: Surgeries Undergoing General Anesthesia
• Intervention / Treatment: Other: Lower FiO2; Other: Intermediate FiO2; Other: Higher FiO2

Detailed Description

The Intraop Ox trial will enroll adult patients undergoing surgery with tracheal intubation. Participating hospitals will be randomly assigned (as a unit) to administer one of three oxygenation strategies during maintenance anesthesia (lower FiO₂ [0.21-0.40], intermediate FiO₂ [0.40-0.80], or higher [FiO₂ 0.80-1.00] each period (month). The primary outcome is a composite of organ injury (acute kidney injury, myocardial injury, lung injury, stroke) or death within 30 days. Secondary outcome is 30-day mortality. Exploratory outcomes are individual components of the composite primary endpoint, surgical site infection, length of stay, and hypoxemia. The study is conducted under a waiver of informed consent due to minimal incremental risk of participating and impracticability of obtaining consent in this cluster-randomized design.

• Study Type: Interventional
• Enrollment (Estimated): 54000
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Tracie Baker, CCRA; Phone Number: 6158751852; Email: tracie.d.baker@vumc.org

Study Locations

• United States
  • Michigan
    • Ann Arbor, Michigan, United States, 48109
      • Not yet recruiting
      • University of Michigan Hospital
      • Contact: Rebecca Pantis, MHSA; Phone Number: 734-834-8318; Email: repantis@med.umich.edu
      • Principal Investigator: Christa Vaughn, MD
  • Nebraska
    • Omaha, Nebraska, United States, 68105
      • Not yet recruiting
      • Nebraska Medical Center
      • Contact: Emely Sanchez, BS; Phone Number: 402-559-8299; Email: emsanchezrodriguez@unmc.edu
      • Principal Investigator: Levi Zehr, MD
  • Tennessee
    • Nashville, Tennessee, United States, 37212
      • Recruiting
      • Vanderbilt University Medical Center
      • Contact: Tracie Baker, CCRA; Phone Number: 6158751852; Email: tracie.d.baker@vumc.org
      • Principal Investigator: Meredith Kingeter, MD
  • Utah
    • Salt Lake City, Utah, United States, 84112
      • Not yet recruiting
      • University of Utah Huntsman Cancer Institute
      • Contact: Anne Mackey, MD; Phone Number: 801-580-6886; Email: Anne.mackey@utah.edu
      • Principal Investigator: Caroline Ruminski, MD

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Patient located in a participating operating room
• Planned surgery includes tracheal intubation

Exclusion Criteria:

• Patient is known to be less than 18 years old
• Patient is known to be pregnant
• Patient is known to be a prisoner.
• Patient is American Society of Anesthesiologists (ASA) classification-6 (i.e., organ donor)
• Patient's planned surgical case includes open heart surgery, defined as surgery on the heart or ascending aorta requiring sternotomy or thoracotomy.
• Patient's planned procedure requires prolonged apnea, bronchoscopy, airway surgery, or one-lung ventilation.
• Patient's planned surgical case includes use of extracorporeal membrane oxygenation (ECMO).
• Patient is known to have a history of bleomycin treatment.
• Patient was enrolled in the trial in the prior 30 days.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Single

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Lower FiO2	Other: Lower FiO2; FiO₂ 0.21-0.40 or lowest FiO₂ to maintain SpO₂ ≥ 94% during maintenance anesthesia
Experimental: Intermediate FiO2	Other: Intermediate FiO2; FiO₂ 0.40-0.80 or lowest FiO₂ to maintain SpO₂ ≥ 94% during maintenance anesthesia
Experimental: Higher FiO2	Other: Higher FiO2; FiO₂ > 0.80 to maintain SpO₂ ≥ 94% during maintenance anesthesia

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Composite of organ injury or in-hospital death within 30 days of surgery	This composite outcome measures the number of participants experiencing at least one of the following organ injuries or death within the defined study period: Acute Kidney Injury (AKI), defined according to creatinine based Kidney Disease Improving Global Outcomes criteria, specifically a 0.3 mg/dL or greater increase within 48 hours or a 50% or greater increase from baseline within seven days of surgery.; Myocardial injury, defined as >99th percentile of normal based on site-specific troponin assay within 72 hours of surgery.; Lung injury, defined using international classification of diseases, ninth revision or tenth revision (ICD-9 or ICD-10) diagnosis codes; Stroke, defined using international classification of diseases, ninth revision or tenth revision (ICD-9 or ICD-10) diagnosis codes; Death within 30 days of surgery	30 days post-surgery

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
30-day mortality	Death from any cause within 30 days of surgery	30 days post-surgery

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Acute kidney injury	Incidence of acute kidney injury (AKI), defined according to creatinine based Kidney Disease Improving Global Outcomes criteria, specifically a 0.3 mg/dL or greater increase from baseline within 48 hours or a 50% or greater increase from baseline within seven days of surgery	7 days post-surgery
Myocardial injury	Myocardial injury, defined as >99th percentile of normal plasma troponin based on site-specific troponin assay within 72 hours of surgery.	72 hours post-surgery
Lung injury	Lung injury, defined using international classification of diseases, ninth revision or tenth revision (ICD-9 or ICD-10) diagnosis codes	30 days post-surgery
Stroke	Stroke, defined using international classification of diseases, ninth revision or tenth revision (ICD-9 or ICD-10) diagnosis codes	30 days post-surgery
Surgical site infection	Surgical site infection, defined using National Surgical Quality Improvement Program (NSQIP) criteria and reported to NSQIP and also captured using international classification of diseases (ICD) diagnosis data.	30 days post-surgery
Hospital length of stay	Total number of calendar days from the date of surgery to the date of discharge following the index procedure.	Day of hospital discharge
Hypoxemia	Incidence and duration of SpO₂ values < 80% (in minutes) during maintenance anesthesia (from anesthesia induction to anesthesia emergence).	Perioperative

Collaborators and Investigators

• Sponsor: Frederic T Billings IV
• Collaborators: University of Michigan; Multicenter Perioperative Outcomes Group; The Association of University Anesthesiologists
• Investigators: Principal Investigator: Frederic T Billings, MD, Vanderbilt University Medical Center

Study record dates

Study Major Dates

• Study Start (Actual): December 1, 2025
• Primary Completion (Estimated): February 1, 2028
• Study Completion (Estimated): April 1, 2028

Study Registration Dates

• First Submitted: October 31, 2025
• First Submitted That Met QC Criteria: October 31, 2025
• First Posted (Actual): November 4, 2025

Study Record Updates

• Last Update Posted (Actual): April 7, 2026
• Last Update Submitted That Met QC Criteria: April 3, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: anesthesia; mechanical ventilation; stroke; myocardial injury; surgery; acute kidney injury; lung injury; oxygen; pragmatic; cluster; organ injury; Intraoperative oxygenation
• Additional Relevant MeSH Terms: Urogenital Diseases; Cerebrovascular Disorders; Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Vascular Diseases; Cardiovascular Diseases; Wounds and Injuries; Male Urogenital Diseases; Kidney Diseases; Urologic Diseases; Female Urogenital Diseases; Female Urogenital Diseases and Pregnancy Complications; Respiratory Tract Diseases; Lung Diseases; Renal Insufficiency; Thoracic Injuries; Stroke; Acute Kidney Injury; Lung Injury
• Other Study ID Numbers: 241806

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data cannot be removed from the MPOG servers where they are stored and analysed. We will review requests for data analyses that use individual patient data, but it would have to be performed inside these servers - i.e., IPD cannot not be shared with others.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No