A Long Axis Approach to the Femoral Artery Block (FAB) for Managing Tourniquet Pain and Hypertension in Below-the-Knee Fracture Surgery (FAB)

Turning the Probe, Changing the View: A Novel Long Axis Approach to the Femoral Artery Block (FAB) for Managing Tourniquet Pain and Hypertension in Below-the-Knee Fracture Surgery: A Prospective, Randomized, Double-Blind Controlled Trial

This is a prospective, randomized, double-blind controlled trial evaluating an ultrasound-guided femoral artery block (FAB) using a long-axis in-plane approach compared with a short-axis approach and a control group.

The study will include adult patients (ASA I-III) undergoing below-the-knee fracture surgery with tourniquet application. All patients will receive standardized anesthesia including sciatic nerve block and total intravenous anesthesia.

Participants will be randomized into three groups: short-axis FAB, long-axis FAB, or control (saline injection). The primary aim is to assess the effectiveness of the long-axis FAB in reducing tourniquet-induced hypertension. Secondary outcomes include hemodynamic stability, analgesic requirements, pain scores, block characteristics, and procedural performance metrics.

Study Overview

• Status: Not yet recruiting
• Conditions: Tourniquet Hypertension
• Intervention / Treatment: Procedure: Femoral artery block - short-axis; Procedure: Femoral artery block - long-axis; Other: Normal saline injection (control)

Detailed Description

Tourniquet application during lower limb orthopedic surgery is associated with significant hemodynamic responses, including pain and tourniquet-induced hypertension (TH), which may increase perioperative cardiovascular risk. Femoral artery block (FAB) is a novel ultrasound-guided regional anesthesia technique targeting the perivascular sympathetic plexus surrounding the femoral artery to attenuate these responses.

Previous studies have described FAB using a short-axis in-plane ultrasound approach. This study proposes a novel long-axis in-plane ultrasound technique, hypothesizing that longitudinal visualization of the femoral artery may improve anatomical alignment with perivascular sympathetic structures, resulting in more effective sympathetic blockade, improved safety, and enhanced clinical efficacy.

This is a prospective, randomized, double-blind controlled trial including adult patients (ASA I-III) scheduled for below-the-knee fracture surgery requiring tourniquet application for at least 45 minutes. After informed consent and baseline assessment, patients will be randomized into three groups: (1) short-axis FAB with ropivacaine, (2) long-axis FAB with ropivacaine, and (3) control group receiving normal saline injection.

All patients will receive standardized anesthetic management including sciatic nerve block at the popliteal level and total intravenous anesthesia using propofol and remifentanil via Target-Controlled Infusion (TCI) under BIS monitoring. Hemodynamic variables (blood pressure and heart rate) will be recorded at predefined intraoperative and postoperative time points. Tourniquet-induced hypertension will be defined as a >30% increase in systolic blood pressure from baseline.

Secondary outcomes include intraoperative opioid and vasopressor requirements, incidence of femoral and saphenous nerve spread, procedural performance metrics (imaging and needling time), postoperative pain scores (VAS), and opioid consumption in the recovery unit.

Data will be analyzed using repeated-measures and comparative statistical models to evaluate differences between groups over time and between interventions.

• Study Type: Interventional
• Enrollment (Estimated): 84
• Phase: Not Applicable

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• Age >18 years
• Physical status ASA I-III
• Fluent in Greek or English
• Scheduled surgery: below-knee fractures
• Tourniquet duration ≥45 minutes

Exclusion Criteria:

• Refusal to participate
• Local inflammation at block site
• Known allergy to study drugs
• Morbid obesity (BMI >40)
• Communication inability
• Systemic neurological disease affecting peripheral nerves
• Chronic pain therapy
• Diabetic neuropathy
• Uncontrolled hypertension

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Short-axis femoral artery block; Ultrasound-guided femoral artery block using short-axis in-plane technique with 10 mL ropivacaine 0.5%.	Procedure: Femoral artery block - short-axis; Ultrasound-guided femoral artery block using short-axis in-plane technique with 10 mL ropivacaine 0.5%.
Experimental: Long-axis femoral artery block; Ultrasound-guided femoral artery block using long-axis in-plane technique with 10 mL ropivacaine 0.5%.	Procedure: Femoral artery block - long-axis; Ultrasound-guided femoral artery block using long-axis in-plane technique with 10 mL ropivacaine 0.5%.
Placebo Comparator: Saline control injection; Ultrasound-guided femoral artery injection using in-plane technique with 10 mL 0.9% normal saline.	Other: Normal saline injection (control); Ultrasound-guided femoral artery injection using 10 mL 0.9% normal saline.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence of tourniquet-induced hypertension	Tourniquet-induced hypertension defined as an increase in systolic blood pressure greater than 30% from baseline values during tourniquet application.	From tourniquet inflation to 90 minutes intraoperatively

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Heart rate	Changes in heart rate during tourniquet application at predefined time points.	From tourniquet inflation to 90 minutes intraoperatively
Intraoperative esmolol consumption	Total dose of esmolol administered for treatment of hypertension during surgery.	Intraoperative period
Intraoperative remifentanil consumption	Total remifentanil dose administered during surgery.	Intraoperative period
Postoperative pain score (VAS)	Pain intensity measured using Visual Analog Scale (0-10) in the recovery unit.	0-60 minutes postoperative
Morphine consumption in recovery unit	Total morphine dose required for rescue analgesia in the postoperative recovery period.	0-60 minutes postoperative
Femoral nerve block spread	Incidence of unintended femoral nerve blockade assessed by quadriceps strength and sensory testing.	Immediate postoperative period
Saphenous nerve block spread	Incidence of sensory block in saphenous nerve distribution assessed by pinprick test.	Immediate postoperative period
Imaging time	Time from ultrasound probe placement to optimal image acquisition.	During FAB block procedure
Needling time	Time from needle insertion to completion of local anesthetic or saline injection.	During FAB block procedure
Total block performance time	Total time required for ultrasound imaging, needle placement and completion of local anesthetic or saline injection.	During FAB block procedure

Collaborators and Investigators

• Sponsor: National and Kapodistrian University of Athens

Study record dates

Study Major Dates

• Study Start (Estimated): May 1, 2026
• Primary Completion (Estimated): October 1, 2027
• Study Completion (Estimated): February 1, 2028

Study Registration Dates

• First Submitted: April 16, 2026
• First Submitted That Met QC Criteria: April 16, 2026
• First Posted (Actual): April 23, 2026

Study Record Updates

• Last Update Posted (Actual): April 30, 2026
• Last Update Submitted That Met QC Criteria: April 29, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: randomized controlled trial; sciatic nerve block; Tourniquet pain; FAB block; Tourniquet-induced hypertension; Below-knee fracture surgery; Sympathetic blockade; intraoperative hypertension
• Additional Relevant MeSH Terms: Pharmaceutical Preparations; Crystalloid Solutions; Isotonic Solutions; Solutions; Saline Solution
• Other Study ID Numbers: 802/30-12-2025

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No