Feasibility and Clinical Utility of Paired Non-Invasive Hemodynamic and Tissue Oximetry Monitoring to Detect Limb Ischemia in Lithotomy-Positioned Surgeries (LIMB)

The LIMB Study is a prospective, observational pilot study evaluating the feasibility of combined non-invasive hemodynamic and lower-limb tissue oximetry monitoring during prolonged minimally invasive pelvic surgeries performed in lithotomy position. Thirty patients will undergo continuous intraoperative monitoring, with the primary outcome being the frequency and duration of tissue oxygen desaturation events and secondary outcomes examining correlations with postoperative limb pain, sensation, and motor function. The study is non-interventional, poses minimal risk, and aims to generate preliminary data to inform future strategies for early detection and prevention of limb ischemia and well-leg compartment syndrome

Study Overview

• Status: Recruiting
• Conditions: Neuropathy;Peripheral; Limb Ischemia
• Intervention / Treatment: Other: Lower-Extremity Perfusion Monitoring

Detailed Description

Well-leg compartment syndrome (WLCS) is a rare but potentially devastating complication associated with prolonged surgical procedures performed in the lithotomy position. Prolonged limb elevation, external compression, and reduced perfusion pressure can lead to muscle ischemia, nerve injury, and long-term functional impairment. Early clinical detection of limb ischemia is challenging in anesthetized patients, as classic signs and symptoms often present late in the disease course. As a result, subclinical ischemic events may go unrecognized until postoperative neurologic or motor deficits are identified.

Near-infrared spectroscopy (NIRS)-based tissue oximetry and continuous non-invasive hemodynamic monitoring have emerged as promising technologies for early detection of tissue hypoperfusion. The Edwards Acumen IQ non-invasive hemodynamic monitoring system provides continuous beat-to-beat blood pressure and derived cardiovascular parameters, while the ForeSight IQ tissue oximetry system provides absolute tissue oxygen saturation (StO₂) measurements without the need for a baseline calibration. These systems are FDA-cleared and currently used in clinical settings such as extracorporeal membrane oxygenation (ECMO), where reductions in tissue oxygenation have been shown to correlate with limb ischemia.

This prospective, observational pilot study is designed to evaluate the feasibility and clinical utility of combining continuous non-invasive hemodynamic monitoring with bilateral lower-extremity tissue oximetry in patients undergoing prolonged minimally invasive pelvic surgery in the lithotomy position. The study is non-interventional, and no changes to intraoperative or postoperative clinical management will be made based on monitoring data.

A total of 30 adult patients undergoing minimally invasive hysterectomy, myomectomy, or endometriosis surgery in lithotomy position with an anticipated operative duration greater than two hours will be enrolled at a single academic medical center. Patients who are pregnant, undergoing open procedures, expected to have surgery lasting less than two hours, or who have a known allergy to medical adhesives will be excluded. No vulnerable populations will be enrolled.

After informed consent is obtained in the preoperative area, patients will undergo standard anesthesia and surgical care. Following induction of anesthesia, bilateral ForeSight IQ tissue oximetry sensors will be placed longitudinally over the medial calf muscles, and an Acumen IQ finger cuff will be applied for continuous non-invasive hemodynamic monitoring. Devices will be calibrated, and baseline hemodynamic and tissue oxygenation values will be recorded prior to surgical positioning. Continuous monitoring will be maintained throughout the intraoperative period.

The primary outcome is the occurrence and duration of intraoperative lower-extremity tissue oxygen desaturation events, defined as either a greater than 15% decrease from baseline StO₂ or an absolute StO₂ value below 50% sustained for more than five minutes. These events will be recorded retrospectively from device output and analyzed descriptively.

Secondary outcomes include the correlation between intraoperative tissue oxygenation changes and postoperative lower-extremity symptoms. In the post-anesthesia care unit (PACU), patients will complete a brief standardized assessment rating limb sensation, pain, and motor function on a 5-point Likert scale prior to discharge. The electronic medical record will be reviewed for up to 30 days postoperatively to identify any documented neurologic or musculoskeletal complications related to lower-extremity perfusion.

Demographic data, surgical characteristics, and known risk factors for limb ischemia will be collected from the electronic health record and stored in a secure REDCap database. Data will be de-identified for analysis, with linkage logs stored separately and securely.

As this is an observational feasibility study, no direct clinical benefit is expected for participants. Risks are minimal and primarily related to potential skin irritation from adhesive sensors. No study-related interventions are performed. Study findings may inform future protocols aimed at early detection and prevention of limb ischemia during prolonged surgeries in lithotomy position.

• Study Type: Observational
• Enrollment (Estimated): 30

Contacts and Locations

• Study Contact: Name: Randa Jalloul, MD, MS; Phone Number: 7134867700; Email: randa.j.jalloul@uth.tmc.edu

Study Locations

• United States
  • Texas
    • Houston, Texas, United States, 77027
      • Not yet recruiting
      • Memorial Hermann Medical Center
      • Contact: Randa Jalloul, MD, MS; Phone Number: 7134867700; Email: randa.j.jalloul@uth.tmc.edu
    • Houston, Texas, United States, 77401
      • Recruiting
      • Memorial Hermann Hospital
      • Contact: Randa Jalloul, MD; Phone Number: (713) 486-7700; Email: randa.j.jalloul@uth.tmc.edu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult; Older Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

The study population consists of 30 adult patients undergoing minimally invasive pelvic surgery-including hysterectomy, myomectomy, or endometriosis surgery-performed in the lithotomy position at a single tertiary care center. Eligible patients are those whose procedures are expected to last longer than two hours, placing them at potential risk for lower-limb ischemia related to prolonged positioning. This cohort represents a typical gynecologic surgical population without inclusion of pregnant or other vulnerable individuals

Description

Inclusion Criteria:

1. Adult patients
2. Undergoing minimally invasive pelvic surgery (such as hysterectomy, myomectomy, or endometriosis surgery)
3. Surgery performed in lithotomy position
4. Expected surgical duration > 2 hours as determined by the primary surgeon

Exclusion Criteria:

1. Pregnant patients
2. Procedures expected to last < 2 hours
3. Open surgical approaches
4. Minor procedures
5. Known allergy or sensitivity to adhesives used for monitoring sensors
6. Vulnerable populations (incarcerated, elderly or pregnant)

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort

Intervention / Treatment

Prolonged Lithotomy Surgery Cohort

Other: Lower-Extremity Perfusion Monitoring; This study involves non-interventional physiologic monitoring only, with no alteration to standard surgical or anesthetic care. After induction of anesthesia, patients will have a non-invasive finger cuff applied for continuous beat-to-beat blood pressure and hemodynamic monitoring, along with bilateral lower-leg tissue oximetry sensors placed over the medial calf to continuously measure tissue oxygen saturation (StO₂) throughout surgery. The monitoring data are recorded for observational analysis only, and postoperative limb pain, sensation, and motor function are assessed once in the recovery unit using standardized 5-point Likert scales

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
StO₂ desaturation episodes	Intraoperative lower-limb tissue oxygenation events, defined as the number and duration of StO₂ desaturation episodes, including a drop >15% from baseline or an absolute StO₂ <50% lasting more than 5 minutes, recorded continuously during surgery	Duration of the surgery

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Postoperative lower-limb symptoms- Pain	Postoperative lower-limb symptoms assessed in the post-anesthesia care unit using the following rating scale range 1 through 5, the higher the better.; No sensation (completely numb); Severely reduced sensation; Moderately reduced sensation; Slightly reduced sensation; Normal sensation	up to 2 hours
Postoperative lower-limb symptoms-Motor	Rated using the following scale (range 1-5), higher is better,; No movement (complete paralysis); Severe motor impairment; Moderate motor impairment; Slight motor impairment; Normal movement	up to 2 hours post surgery
Post-operative Limb symptom- sensation	Using the following scale range 1-5, higher is worst.; No pain; Mild pain; Moderate pain; Severe pain; Worst possible pain	up to 2 hours after surgery

Collaborators and Investigators

• Sponsor: The University of Texas Health Science Center, Houston

Study record dates

Study Major Dates

• Study Start (Actual): January 29, 2026
• Primary Completion (Estimated): June 30, 2026
• Study Completion (Estimated): December 1, 2026

Study Registration Dates

• First Submitted: January 27, 2026
• First Submitted That Met QC Criteria: January 27, 2026
• First Posted (Actual): February 4, 2026

Study Record Updates

• Last Update Posted (Actual): May 14, 2026
• Last Update Submitted That Met QC Criteria: May 12, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: nerve injury; trendelemberg; position nerve injury; prolonged surgery
• Additional Relevant MeSH Terms: Nervous System Diseases; Neuromuscular Diseases; Peripheral Nervous System Diseases; Neuritis
• Other Study ID Numbers: HSC-MS-25-0372

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