Continuous Versus Intermittent Ward Monitoring (CONSTANT)

Continuous Versus Intermittent Ward Monitoring on Vital Sign Abnormalities, Clinical Interventions, and Serious Complications: the CONSTANT Trial

The investigators will randomize adults having major non-cardiac inpatient surgery to blinded versus unblinded continuous postoperative vital sign monitoring (saturation, ventilation, and heart rate). The investigators will use a wearable, untethered, and battery-powered sensor (Masimo Radius PPG, Masimo, Irvine, CA) that wirelessly connects to a Masimo monitor and continuously records saturation, ventilation, and pulse rate.

The primary outcome will be areas-exceeding-thresholds for desaturation (<85%), bradypnea (<7 breaths/min), tachypnea (>30 breaths/min), tachycardia (heart rate >130 beats/min), and bradycardia (heart rate <45 beats/min). These exposure thresholds represent a balance between events that are clinically meaningful and excessive alarms that will discourage clinician participation. The investigators expect about 1 alert per patient per day with these thresholds, with most being considered informative or actionable by nurses. In unblinded patients, clinician alerts will be activated at these thresholds.

Study Overview

• Status: Not yet recruiting
• Conditions: Surgery
• Intervention / Treatment: Device: Blinded continuous vital sign monitoring; Device: Unblinded continuous vital sign monitoring

Detailed Description

Postoperative cardiovascular mortality remains common, and two-thirds occurs during the initial hospitalization. Deterioration typically occurs over hours but is usually unrecognized because vital signs are evaluated a 4-6-hour intervals, just as they were a half-century ago when patient acuity was much lower. Recognition of even subtle changes in basic vital signs may allow clinicians to detect cardiopulmonary deterioration well before serious adverse events occur. Consequent clinical interventions may in turn prevent complications, or at least moderate their severity. The investigators therefore propose a single-center randomized trial of continuous ward monitoring.

The investigators will randomize adults having major non-cardiac inpatient surgery to blinded versus unblinded continuous saturation, ventilation, and heart rate monitoring. Postoperative cardiovascular mortality remains common, and a third occurs during the initial hospitalization. Deterioration occurs over many hours but is usually unrecognized because vital signs are evaluated 4-6-hour intervals, just as they were a half-century ago when patient acuity was much lower. Recognition of even subtle changes in basic vital signs may allow clinicians to detect cardiopulmonary deterioration well before serious adverse events occur. Consequent clinical interventions may in turn prevent complications, or at least moderate their severity. The investigators therefore propose a single-center randomized trial of continuous ward monitoring.

The Investigators will randomize adults having major non-cardiac inpatient surgery to blinded versus unblinded continuous postoperative vital sign monitoring (saturation, ventilation, and heart rate). The investigators will use a wearable, untethered, and battery-powered sensor (Masimo Rad-97 with Radius PPG Tetherless Pulse oximetry system, Masimo, Irvine, CA) that wirelessly connects to a work station and continuously records saturation, ventilation, and pulse rate.

The primary outcome will be areas-exceeding-thresholds for desaturation (<85%), bradypnea (<7 breaths/min), tachypnea (>30 breaths/min), tachycardia (heart rate >130 beats/min), and bradycardia (heart rate <45 beats/min). These exposure thresholds represent a balance between events that are clinically meaningful and excessive alarms that will discourage clinician participation. The investigators expect about 2 alerts per patient per day with these thresholds, with most being considered informative or actionable by nurses. In unblinded patients, clinician alerts will be activated at these thresholds.

Secondarily, the investigators will evaluate a composite of clinical interventions for desaturation, bradypnea, tachypnea, tachycardia, and bradycardia. On an exploratory basis, as a pilot for a future major multi-center outcome trial, The investigators will evaluate a composite of major complications including naloxone administration, rapid-response team activation, unplanned ICU transfer, and mortality within 7 postoperative days.

The innovative long-term goal is to reduce in-hospital postoperative cardiovascular and pulmonary mortality. Specifically, The investigators expect to show that continuous rather than intermittent postoperative vital sign monitoring identifies unstable patients which will allow clinicians to intervene and prevent serious complications and death - thus promoting longer and healthier lives.

• Study Type: Interventional
• Enrollment (Estimated): 492
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Valerie L Anderson, BS; Phone Number: (713) 500-4383; Email: Valerie.L.Anderson@uth.tmc.edu
• Study Contact Backup: Name: Daniel Sessler, MD; Phone Number: 713-500-3062; Email: Daniel.Sessler@uth.tmc.edu

Study Locations

• United States
  • Texas
    • Houston, Texas, United States, 77030
      • The University of Texas Health Science Center at Houston
      • Contact: Valerie L Anderson, BS; Phone Number: (713) 500-4383; Email: Valerie.L.Anderson@uth.tmc.edu
      • Principal Investigator: Daniel I Sessler, M.D.

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

1. Are admitted to one of the wards equipped with the Masimo Radius PPG and Rad-97 monitors;
2. Are ≥18 years old;
3. Are designated American Society of Anesthesiologists physical status 1-4;
4. Had major noncardiac surgery lasting at least 1.5 hours;
5. Are expected to remain hospitalized at least two postoperative nights;
6. Had general anesthesia with or without neuraxial anesthesia.

Exclusion Criteria:

1. Have language, vision, or hearing impairments that may compromise continuous monitoring;
2. Are designated Do Not Resuscitate, hospice, or receiving end of life care;
3. Have previously participated in the study.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Sham Comparator: Blinded continuous vital sign monitoring; Continuous ward monitoring with vital signs recorded but not available to patients, clinicians, or investigators.	Device: Blinded continuous vital sign monitoring; Continuous ward monitoring with vital signs recorded but not available to patients, clinicians, or investigators.
Experimental: Unblinded continuous vital sign monitoring; Continuous ward monitoring with vital signs available to clinicians and investigators.	Device: Unblinded continuous vital sign monitoring; Continuous ward monitoring with vital signs available to clinicians and investigators.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Vital sign abnormalities with routine hospital monitors	Area of vital sign abnormalities exceeding defined thresholds.	48 postoperative hours

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Interventions	The incidence of a composite of clinical interventions for desaturation, hypoventilation, tachypnea, tachycardia, bradycardia, and hypotension within 48 hours after major non-cardiac surgery.	48 postoperative hours

Collaborators and Investigators

• Sponsor: The University of Texas Health Science Center, Houston
• Collaborators: Masimo Corporation
• Investigators: Principal Investigator: Daniel Sessler, MD, The University of Texas Health Science Center, Houston

Study record dates

Study Major Dates

• Study Start (Estimated): June 1, 2026
• Primary Completion (Estimated): July 1, 2028
• Study Completion (Estimated): March 1, 2029

Study Registration Dates

• First Submitted: January 22, 2024
• First Submitted That Met QC Criteria: January 22, 2024
• First Posted (Actual): January 31, 2024

Study Record Updates

• Last Update Posted (Actual): May 28, 2026
• Last Update Submitted That Met QC Criteria: May 24, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Surgery; Postoperative; monitoring; Vital signs
• Other Study ID Numbers: HSC-MS-24-0978

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Data will be shared on a collaborative basis with approval of the Steering Committee and data-use agreement.

Drug and device information, study documents

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