Study of QL Analgesic Response and Extent (SQUARE)

Anterior Versus Posterior Versus Lateral Quadratus Lumborum Block: a Randomized Control Trial in Healthy Volunteers

A total of 14-18 healthy volunteers will be included. There will be three different procedure days, separated by at least one week. On each visit, the subjects will receive a QL block, according to the randomization process. Each volunteer will undergo pre-procedure screening on the first visit. The blocks will be performed on the same side, by the same anesthesiologist, with at least one week between each block. An anterior QL block will be administered on one day, a posterior QL block on another, and a lateral QL block on the third. The order will be randomized, and both the subject and the research team member assessing the block will be blinded. To compare the dermatomal sensory block distribution, the investigators will use detailed mapping with pinprick, cold, and heat stimuli. A handheld dynamometric assessment of lower extremity strength. The testing will be performed 60 to 90 minutes after performance of the blocks.

Study Overview

• Status: Not yet recruiting
• Conditions: Postoperative Pain; Acute Pain; Regional Anesthesia Block
• Intervention / Treatment: Combination product: Quadratus Lumborum with 1.5% Lidocaine

Detailed Description

Regional anesthesia techniques are widely employed to achieve sensory blockade of the abdominal wall. Among these, the epidural remains the most well-established approach, offering bilateral spread. However, its association with neuraxial complications has led to a decline in its clinical use. In contrast, fascial plane blocks, avoid neuraxial-related risks. The advent of ultrasound-guided blocks has sparked growing interest in novel fascial plane blocks, that can deliver multi-dermatomal with a lower rate of complications.

Three Quadratus Lumborum (QL) blocks are an example of these fascial plane blocks, commonly performed for abdominal and pelvic surgery. Despite their widespread clinical use, no prior studies have directly compared the three techniques in terms of their cutaneous distribution. Additionally, case reports note that lower extremity weakness can sometimes temporarily occur as a result of accidental spread to the lumbar plexus. Thus, this randomized, double-blinded trial aims to investigate the cutaneous distribution of these three blocks in healthy adult volunteers. Lastly, this study will assess the incidence and severity of lower extremity weakness that may occur with each technique. In addition, this study also seeks to investigate the pharmacokinetics (PK) of lidocaine in each technique. The rationale for this lies in the anatomical differences between the blocks. Theoretically, there may be a difference in the anatomical target for these blocks, but the investigators hypothesize that there is no difference in the local anesthetic absorption. Therefore, as the investigators expect similar systemic absorption, the chances of local anesthetic systemic toxicity (LAST) should be equally low, and all blocks should be similarly safe.

• Study Type: Interventional
• Enrollment (Estimated): 25
• Phase: Phase 4

Contacts and Locations

• Study Contact: Name: Brian Mendelson, MD; Phone Number: 818-456-7040; Email: brian.mendelson@duke.edu

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• Ability to provide written informed consent
• Ability and willingness to comply with the study procedures and duration requirements
• ASA physical status 1 or 2
• Age ≥ 18 years
• Weight > 70kg

Exclusion Criteria:

• BMI > 35kg.m2
• Use of analgesics within 24 hours before the procedure
• History of thoracic trauma or surgery
• Abdominal deformities or abnormalities that may prevent proper block performance
• Abdominal tattoos in the area of block performance
• Systemic neuromuscular disease
• Contraindications to regional anesthesia (e.g., infection, allergy, challenging sonoanatomy)
• Structures are unable to be visualized by ultrasound
• Pregnancy
• Other known health conditions that would affect the participant's ability to successfully complete the study

Study Plan

How is the study designed?

Design Details

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

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Lateral Quadratus Lumborum block; Participants receive quadratus lumborum block under ultrasound guidance, with 30mL of 1.5% lidocaine on one visit.	Combination product: Quadratus Lumborum with 1.5% Lidocaine; For the anterior QL block, a curvilinear probe and nerve stimulator will be used. Local anesthetic will be deposited anterior to the QL muscle but posterior to the psoas muscle. A nerve stimulator at 2 Hz frequency, 1.5 mA will be used to aid in identification of intramuscular placement of the needle. Local anesthetic will only be deposited if no twitch is seen in either the QL or psoas muscle with an appropriate circuit formed. For the posterior QL block, a linear or curvilinear probe will be used, at the discretion of the anesthesiologist. Local anesthetic will be deposited posterior to the QL muscle such that anterior depression of the muscle is seen. For the lateral QL block, local anesthetic will be deposited lateral to the QL muscle.
Experimental: Anterior Quadratus Lumborum Block; Participants receive anterior quadratus lumborum block under ultrasound guidance, with 30mL of 1.5% lidocaine on one visit.	Combination product: Quadratus Lumborum with 1.5% Lidocaine; For the anterior QL block, a curvilinear probe and nerve stimulator will be used. Local anesthetic will be deposited anterior to the QL muscle but posterior to the psoas muscle. A nerve stimulator at 2 Hz frequency, 1.5 mA will be used to aid in identification of intramuscular placement of the needle. Local anesthetic will only be deposited if no twitch is seen in either the QL or psoas muscle with an appropriate circuit formed. For the posterior QL block, a linear or curvilinear probe will be used, at the discretion of the anesthesiologist. Local anesthetic will be deposited posterior to the QL muscle such that anterior depression of the muscle is seen. For the lateral QL block, local anesthetic will be deposited lateral to the QL muscle.
Experimental: Posterior Quadratus Lumborum Block; Participants receive posterior quadratus lumborum block under ultrasound guidance, with 30mL of 1.5% lidocaine on one visit.	Combination product: Quadratus Lumborum with 1.5% Lidocaine; For the anterior QL block, a curvilinear probe and nerve stimulator will be used. Local anesthetic will be deposited anterior to the QL muscle but posterior to the psoas muscle. A nerve stimulator at 2 Hz frequency, 1.5 mA will be used to aid in identification of intramuscular placement of the needle. Local anesthetic will only be deposited if no twitch is seen in either the QL or psoas muscle with an appropriate circuit formed. For the posterior QL block, a linear or curvilinear probe will be used, at the discretion of the anesthesiologist. Local anesthetic will be deposited posterior to the QL muscle such that anterior depression of the muscle is seen. For the lateral QL block, local anesthetic will be deposited lateral to the QL muscle.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of participants with blocked areas as measured by skin temperature discrimination	Skin temperature assessment using gloved ice on the chest wall, to discriminate blocked vs unblock areas.	60 to 90 minutes post-block
Number of participants with blocked areas as measured by mechanical discrimination	Mechanical assessment using a neuropin (pinprick) on the chest wall, to discriminate blocked vs unblock areas.	60 to 90 minutes post-block
Blocked area as measured by cutaneous distribution mapping	Mapping the blocked area (using the previous temperature and mechanical assessments, demarcating lines on the skin) to calculate the area blocked.	60 to 90 minutes post-block

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Skin temperature of the chest wall	Infrared camera will assess skin temperature of the chest wall.	60 to 90 minutes post-block
Blocked area as measured by nociceptive discrimination	Nociceptive stimuli will be delivered using controlled heat to discriminate blocked versus unblocked areas on the chest wall.	60 to 90 minutes post-block
Lidocaine systemic absorption	Calculate lidocaine systemic absorption (Cmax).	0, 30, 60, 120, and 240 minutes after lidocaine administration

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of participants with block-related Adverse Events	Any block-related adverse events will be recorded.	End of study (2 days post blocks)

Collaborators and Investigators

• Sponsor: Duke University
• Investigators: Principal Investigator: Brian Mendelson, MD, Duke University

Study record dates

Study Major Dates

• Study Start (Estimated): May 1, 2026
• Primary Completion (Estimated): November 1, 2026
• Study Completion (Estimated): December 1, 2026

Study Registration Dates

• First Submitted: April 29, 2026
• First Submitted That Met QC Criteria: April 29, 2026
• First Posted (Actual): May 5, 2026

Study Record Updates

• Last Update Posted (Actual): May 5, 2026
• Last Update Submitted That Met QC Criteria: April 29, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Regional anesthesia; QL block; QL; Quadratus lumborum block; Quadratus lumborum; Fascial plane block; Abdominal blocks
• Additional Relevant MeSH Terms: Pain; Neurologic Manifestations; Postoperative Complications; Pathologic Processes; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Pain, Postoperative; Acute Pain; Organic Chemicals; Anilides; Amides; Aniline Compounds; Amines; Acetanilides; Lidocaine
• Other Study ID Numbers: Pro00118381

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