Analysis of Factors Influencing Epidural Depth in Patients Undergoing Percutaneous Nephrolithotomy and Development of a Predictive Model

July 5, 2026 updated by: Hongbo Zheng, Tongji Hospital
Accurate estimation of epidural depth is critical for safe epidural anesthesia during percutaneous nephrolithotomy (PCNL). Although various imaging modalities can predict epidural depth, they increase healthcare burden and are not always feasible in emergency or bedside settings. Identifying simple, easily obtainable clinical parameters-such as sex, age, and body mass index (BMI)-for predicting epidural depth has become a research priority. However, systematic investigations specifically targeting the Chinese population remain scarce. This retrospective study aims to identify independent factors influencing epidural depth in PCNL patients and to develop simple, level-specific predictive models for different puncture sites, thereby providing a practical reference for clinical epidural anesthesia.

Study Overview

Status

Not yet recruiting

Conditions

Detailed Description

Percutaneous nephrolithotomy (PCNL) is the standard minimally invasive surgical procedure for removal of kidney stones larger than 2 cm and is established as the gold standard for the management of complex renal calculi. This procedure may be performed under either general anesthesia or regional anesthesia, including epidural or spinal anesthesia. Accumulating meta-analyses have demonstrated that, compared with general anesthesia, regional anesthesia is associated with reduced postoperative pain scores and lower total hospital costs, without compromising the stone-free rate. Furthermore, in awake patients undergoing regional anesthesia, respiratory movements may generate a so-called "respiratory-synchronous stone fragmentation effect," which facilitates the expulsion of stone debris.

Successful epidural anesthesia relies critically on accurate identification of the epidural space and precise control of puncture depth. Insufficient puncture depth may result in improper catheter placement and subsequent block failure, whereas excessive puncture depth increases the risk of dural puncture, leading to cerebrospinal fluid leakage and post-dural puncture headache. In severe cases, inadvertent injection of a large dose of local anesthetics into the subarachnoid space can cause life-threatening cardiovascular and respiratory depression. Therefore, preprocedural estimation of the skin-to-epidural space distance is of considerable clinical importance.

Although racial differences in epidural depth have been reported, systematic investigations specifically targeting the Chinese population remain scarce. Various imaging modalities, including computed tomography, magnetic resonance imaging, and ultrasound, can be used to predict epidural depth. However, these examinations increase healthcare burden and are not always feasible in emergency or bedside settings. Consequently, identifying simple, easily obtainable clinical parameters-such as sex, age, and body mass index (BMI)-for predicting epidural depth has become a research priority.

In this context, the present study aimed to identify factors influencing epidural depth through a retrospective analysis of clinical data from PCNL patients and to develop simple, level-specific predictive models for different puncture sites, thereby providing a practical reference for clinical epidural anesthesia.

Study Type

Observational

Enrollment (Estimated)

3278

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

Study Locations

  • China
    • Hubei
      • Wuhan, Hubei, China, 430030
        • Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology
        • Contact:
        • 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

Sampling Method

Non-Probability Sample

Study Population

This study retrospectively enrolled adult patients who underwent percutaneous nephrolithotomy (PCNL) under continuous epidural anesthesia between January 2014 and December 2025. Inclusion criteria were: (1) age ≥ 18 years; (2) successful epidural puncture and catheter placement using the midline approach; (3) clear documentation of puncture level and puncture depth in the anesthesia record. Exclusion criteria were: (1) dural puncture during anesthesia (including those who subsequently had a successful repuncture); (2) use of the paramedian approach for epidural puncture; (3) uncertain epidural anesthesia effect requiring combined general anesthesia; (4) incomplete clinical data.

Description

Inclusion Criteria:

  • (1) age ≥ 18 years; (2) successful epidural puncture and catheter placement using the midline approach; (3) clear documentation of puncture level and puncture depth in the anesthesia record.

Exclusion Criteria:

  • (1) dural puncture during anesthesia (including those who subsequently had a successful repuncture); (2) use of the paramedian approach for epidural puncture; (3) uncertain epidural anesthesia effect requiring combined general anesthesia; (4) incomplete clinical data.

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

Cohorts and Interventions

Group / Cohort
T11-T12
On operating room admission, after providing written informed consent for anesthesia, patients underwent standard monitoring (ECG, NIBP, pulse oximetry). Baseline demographic and anthropometric data, including hospital admission ID, sex, height, and weight, were recorded, and body mass index (BMI) was calculated. After positioning in the lateral decubitus position, the T11-T12 interspace was selected for puncture using a midline approach, and the loss-of-resistance technique confirmed epidural space entry. Puncture depth (skin-to-epidural space) was recorded from needle shaft markings to the nearest 0.1 cm.
T12-L1
On operating room admission, after providing written informed consent for anesthesia, patients underwent standard monitoring (ECG, NIBP, pulse oximetry). Baseline demographic and anthropometric data, including hospital admission ID, sex, height, and weight, were recorded, and body mass index (BMI) was calculated. After positioning in the lateral decubitus position, the T12-L1 interspace was selected for puncture using a midline approach, and the loss-of-resistance technique confirmed epidural space entry. Puncture depth (skin-to-epidural space) was recorded from needle shaft markings to the nearest 0.1 cm.
L1-L2
On operating room admission, after providing written informed consent for anesthesia, patients underwent standard monitoring (ECG, NIBP, pulse oximetry). Baseline demographic and anthropometric data, including hospital admission ID, sex, height, and weight, were recorded, and body mass index (BMI) was calculated. After positioning in the lateral decubitus position, the L1-L2 interspace was selected for puncture using a midline approach, and the loss-of-resistance technique confirmed epidural space entry. Puncture depth (skin-to-epidural space) was recorded from needle shaft markings to the nearest 0.1 cm.
L2-L3
On operating room admission, after providing written informed consent for anesthesia, patients underwent standard monitoring (ECG, NIBP, pulse oximetry). Baseline demographic and anthropometric data, including hospital admission ID, sex, height, and weight, were recorded, and body mass index (BMI) was calculated. After positioning in the lateral decubitus position, the L2-L3 interspace was selected for puncture using a midline approach, and the loss-of-resistance technique confirmed epidural space entry. Puncture depth (skin-to-epidural space) was recorded from needle shaft markings to the nearest 0.1 cm.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
epidural depth
Time Frame: during epidural anesthesia
epidural depth
during epidural anesthesia

Collaborators and Investigators

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

Sponsor

Tongji Hospital

Investigators

  • Principal Investigator: Hongbo Zheng, MM, Tongji Hospital

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)

June 30, 2026

Primary Completion (Estimated)

August 31, 2026

Study Completion (Estimated)

August 31, 2026

Study Registration Dates

First Submitted

July 5, 2026

First Submitted That Met QC Criteria

July 5, 2026

First Posted (Actual)

July 10, 2026

Study Record Updates

Last Update Posted (Actual)

July 10, 2026

Last Update Submitted That Met QC Criteria

July 5, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Other Study ID Numbers

  • EDPN

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

Individual participant data that underlie the results reported in this article, after deidentification (text, tables,figures, and appendices).

IPD Sharing Time Frame

Immediately followingpublication. No end date.

IPD Sharing Access Criteria

Anyone who wishes to access the data.

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL
  • SAP

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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