An interventional study of Ultrasound-Guided Upper Rectus Sheath Block (20 mL) and Ultrasound-Guided Upper Rectus Sheath Block (30 mL) in Cutaneous Sensory Blockade, sponsored by Chiang Mai University. Not yet recruiting at 1 site in Thailand. Open to participants aged 20 Years and older. Per ClinicalTrials.gov, last updated 2026-10-15.
Sponsored by Chiang Mai University · Not applicable, Interventional, and Treatment
This randomized controlled study aims to evaluate the effects of local anesthetic injection volume and injection site on cutaneous sensory distribution following ultrasound-guided rectus sheath block (RSB). Participants undergoing laparoscopic abdominal surgery will be randomized to receive RSB using different injection sites and volumes (20 mL or 30 mL per side). Injection sites will be selected according to the surgical location, including upper, middle, or lower rectus sheath approaches. Cutaneous sensory distribution will be assessed to determine the extent and pattern of sensory blockade associated with each technique.
The findings may help optimize injection techniques and local anesthetic volumes to achieve adequate sensory coverage for abdominal surgery.
Rectus sheath block (RSB) is an ultrasound-guided regional anesthesia technique used to provide analgesia for laparoscopic abdominal surgery. Local anesthetic is injected between the rectus abdominis muscle and the posterior rectus sheath to block the anterior cutaneous branches of the thoracoabdominal nerves. Although RSB is commonly used for perioperative analgesia, the optimal injection site and local anesthetic volume required to achieve adequate cutaneous sensory distribution remain uncertain.
This prospective, randomized study aims to investigate the effects of local anesthetic injection volume and injection site on the extent and pattern of cutaneous sensory blockade following ultrasound-guided RSB in patients undergoing laparoscopic abdominal surgery.
A total of 120 participants will be enrolled and stratified according to the surgical location into two strata: upper abdominal surgery (US) and lower abdominal surgery (LS). Within each stratum, participants will be randomly allocated to one of four groups using a computer-generated randomization sequence with variable block sizes and a 2:2:1:1 allocation ratio.
In the upper abdominal surgery stratum, participants will receive one of the following interventions:
In the lower abdominal surgery stratum, participants will receive one of the following interventions:
All blocks will be performed under ultrasound guidance using 0.25% bupivacaine with epinephrine, according to the assigned injection site and volume.
Following block administration, cutaneous sensory distribution will be systematically assessed to determine the extent and pattern of sensory blockade. The sensory distribution achieved with different injection volumes and injection sites will be compared within each surgical stratum.
The findings of this study may provide evidence to guide the selection of injection sites and local anesthetic volumes for ultrasound-guided RSB and help optimize sensory coverage in patients undergoing abdominal surgery.
1,269 studies on the registry are indexed under Agnosia; 524 are open to participants now.
This study's planned enrollment of 120 is above the median of 75 across 1,089 interventional studies indexed under Agnosia.
Browse Agnosia studies →Chiang Mai University is the lead sponsor of 119 studies on the registry; 12 are open to participants now.
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Exclusion Criteria:
Participants undergoing laparoscopic upper abdominal surgery will receive bilateral ultrasound-guided upper rectus sheath block using 20 mL of local anesthetic per side.
Procedure: Ultrasound-Guided Upper Rectus Sheath Block (20 mL)
Participants undergoing laparoscopic upper abdominal surgery will receive bilateral ultrasound-guided upper rectus sheath block using 30 mL of local anesthetic per side.
Procedure: Ultrasound-Guided Upper Rectus Sheath Block (30 mL)
Participants undergoing either laparoscopic upper or lower abdominal surgery will receive bilateral ultrasound-guided middle rectus sheath block using 20 mL of local anesthetic per side.
Procedure: Ultrasound-Guided Middle Rectus Sheath Block (20 mL)
Participants undergoing either laparoscopic upper or lower abdominal surgery will receive bilateral ultrasound-guided middle rectus sheath block using 30 mL of local anesthetic per side.
Procedure: Ultrasound-Guided Middle Rectus Sheath Block (30 mL)
Participants undergoing laparoscopic lower abdominal surgery will receive bilateral ultrasound-guided lower rectus sheath block using 20 mL of local anesthetic per side.
Procedure: Ultrasound-Guided Lower Rectus Sheath Block (20 mL)
Participants undergoing laparoscopic lower abdominal surgery will receive bilateral ultrasound-guided lower rectus sheath block using 30 mL of local anesthetic per side.
Procedure: Ultrasound-Guided Lower Rectus Sheath Block (30 mL)
Bilateral ultrasound-guided upper rectus sheath block will be performed using 20 mL of 0.25% bupivacaine with epinephrine per side. The local anesthetic will be injected into the plane between the rectus abdominis muscle and the posterior rectus sheath at the upper abdominal injection site.
Bilateral ultrasound-guided upper rectus sheath block will be performed using 30 mL of 0.25% bupivacaine with epinephrine per side. The local anesthetic will be injected into the plane between the rectus abdominis muscle and the posterior rectus sheath at the upper abdominal injection site.
Bilateral ultrasound-guided middle rectus sheath block will be performed using 20 mL of 0.25% bupivacaine with epinephrine per side. The local anesthetic will be injected into the plane between the rectus abdominis muscle and the posterior rectus sheath at the middle abdominal injection site.
Bilateral ultrasound-guided middle rectus sheath block will be performed using 30 mL of 0.25% bupivacaine with epinephrine per side. The local anesthetic will be injected into the plane between the rectus abdominis muscle and the posterior rectus sheath at the middle abdominal injection site.
Bilateral ultrasound-guided lower rectus sheath block will be performed using 20 mL of 0.25% bupivacaine with epinephrine per side. The local anesthetic will be injected into the plane between the rectus abdominis muscle and the posterior rectus sheath at the lower abdominal injection site.
Bilateral ultrasound-guided lower rectus sheath block will be performed using 30 mL of 0.25% bupivacaine with epinephrine per side. The local anesthetic will be injected into the plane between the rectus abdominis muscle and the posterior rectus sheath at the lower abdominal injection site.
Cutaneous Sensory Blockade Area Assessed by Pinprick Testing
The extent of cutaneous sensory blockade following ultrasound-guided rectus sheath block will be assessed using pinprick testing. Areas with reduced or absent pinprick sensation will be identified and mapped to determine the total cutaneous sensory blockade area (CSBA).
Time frame: 30 minutes after surgery
Cutaneous Sensory Blockade Area Assessed by Pinprick Testing
The extent of cutaneous sensory blockade following ultrasound-guided rectus sheath block will be assessed using pinprick testing. Areas with reduced or absent pinprick sensation will be identified and mapped to determine the total cutaneous sensory blockade area (CSBA).
Time frame: 24 hours after block completion
Cutaneous Sensory Blockade Area Assessed by Cold Testing
The extent of cutaneous sensory blockade will be assessed using cold sensation testing. Areas with reduced or absent cold sensation will be identified and mapped to determine the total cutaneous sensory blockade area (CSBA).
Time frame: 30 minutes after surgery and 24 hours after block completion
Number of Dermatomes With Sensory Blockade
The number of dermatomes demonstrating reduced or absent cutaneous sensation following rectus sheath block will be recorded using standardized sensory testing. The total number of dermatomes with sensory blockade will be compared between groups.
Time frame: 30 minutes after surgery and 24 hours after block completion
Dermatomal Distribution of Sensory Blockade
The anatomical distribution of sensory blockade will be evaluated by identifying the dermatomal levels demonstrating reduced or absent sensation following rectus sheath block.
Time frame: 30 minutes after surgery and 24 hours after block completion
Regression of Cutaneous Sensory Blockade Over Time
Changes in cutaneous sensory blockade area over time will be assessed through repeated sensory testing following rectus sheath block.
Time frame: 30 minutes after surgery and 24 hours after block completion
Cumulative Opioid Consumption During the First 24 Postoperative Hours
Total opioid consumption during the first 24 hours after surgery will be recorded and converted to intravenous morphine milligram equivalents (MME).
Time frame: From completion of surgery to 24 hours postoperatively
Postoperative Pain Intensity
Postoperative pain intensity will be assessed using the Numerical Rating Scale (NRS), ranging from 0 (no pain) to 10 (worst imaginable pain).
Time frame: At 2, 6, 12, and 24 hours postoperatively
Time to First Rescue Analgesic Administration
The time from completion of surgery to the first administration of rescue analgesic medication will be recorded in minutes. Participants who do not require rescue analgesia during the observation period will be documented accordingly.
Time frame: From completion of surgery to 24 hours postoperatively.
Incidence of Block-Related Adverse Events
The number and proportion of participants experiencing block-related adverse events will be recorded.
Time frame: From block administration to 24 hours postoperatively
Plan to share: No
Start is estimated for Oct 2026; primary completion for Dec 2027, 14 months later.
Of 606 non-industry interventional studies with no phase under Agnosia, half reached primary completion within 12 months of starting (the median), counting those still running; a quarter within 5 and three quarters within 27. This study's planned 14 months is above that.
Counting every sponsor, half of 615 studies reached it within 12 months; a quarter within 5 and three quarters within 26.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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