Acute Pain, Postoperative Pain, Acute
Conditions
Keywords
Rectus Sheath Block, Abdominal Block, Fascial Plane Block, RSB
Brief summary
Regional anesthesia techniques (or nerve blocks) are used to provide sensory blockade over the abdominal wall. The most established technique is thoracic epidural. This provides bilateral spread but is also associated with neuraxial complications, which has led to a decrease in clinical usage. The rectus sheath block (RSB) is an established regional anesthesia technique used to provide somatic analgesia to the midline anterior abdominal wall by depositing local anesthetic in the posterior rectus sheath, thereby targeting the terminal anterior branches of the lower thoracic intercostal nerves. The conventional approach involves placing the ultrasound (US) probe transversely across the rectus abdominis muscle and advancing the needle in-plane either lateral-to-medial or medial-to-lateral. While this technique achieves spread within the sheath, the cephalocaudal distribution of local anesthetic may be suboptimal, potentially limiting the extent of dermatomal coverage. A longitudinal probe orientation, with needle insertion from cephalad to caudad, may theoretically facilitate a more extensive cranio-caudal spread by aligning the injection axis with the anatomical fascial plane of the posterior rectus sheath. However, the relative efficacy of these two approaches has not been investigated in a controlled, comparative setting. Thus, this randomized, single-blinded trial aims to evaluate the dermatomal sensory distribution and ultrasound-assessed local anesthetic spread achieved by the transverse versus longitudinal in-plane approaches to ultrasound-guided RSB in healthy adult volunteers. To compare the dermatomal sensory block distribution, investigators will use dermatomal mapping with pinprick, and cold.
Detailed description
A total of 14-18 adult volunteers will be included. Each participant will receive bilateral rectus sheath blocks at a standardized supraumbilical level. The side receiving the transverse approach (US probe perpendicular to muscle fibers; needle in-plane lateral-to-medial) and the side receiving the longitudinal approach (US probe parallel to muscle fibers; needle in-plane cephalad-to-caudad) will be randomized. The blocks will be performed with a standardized volume and concentration of local anesthetic, under real-time US guidance by the same experienced anesthesiologist. The research team member assessing the block will be blinded. Immediately after injection of each block, US imaging will be used to assess and measure the length and pattern of spread within the posterior rectus sheath. At baseline and at 60 minutes post-block, dermatomal sensory mapping will be performed using standardized cold and pinprick stimuli over the anterior abdominal wall.
Interventions
DRUG1.0% lidocaine with epinephrine (1:100,000)
The block will be performed by advancing the needle into the posterior rectus sheath compartment, with the local anesthetic deposited posterior to the rectus abdominis muscle and anterior to the posterior rectus sheath. Drug: 20 mL injection of 1.0% lidocaine with epinephrine (1:100,000) on each side (40mL total/subject)
Sponsors
Duke University
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
OTHER
Masking
DOUBLE (Subject, Outcomes Assessor)
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
1. Ability to provide written informed consent 2. Ability and willingness to comply with the study procedures and duration requirements 3. ASA physical status 1 or 2 4. Age ≥ 18 years 5. Weight \> 60kg
Exclusion criteria
1. BMI \> 40kg.m-2 2. Use of analgesics within 24 hours before the procedure 3. History of abdominal trauma or surgery 4. Abdominal deformities or abnormalities that may prevent proper block performance 5. Abdominal tattoos in the supraumbilical area 6. Systemic neuromuscular disease 7. Contraindications to regional anesthesia (e.g., infection, allergy) 8. Structures are unable to be visualized by ultrasound 9. Pregnancy 10. Other known health conditions that would affect the participant's ability to successfully complete the study
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Temperature discrimination | 60 to 90 minutes post-block | Skin temperature assessment using gloved ice on the chest wall, to discriminate blocked vs unblock areas. |
| Mechanical discrimination | 60 to 90 minutes post-block | Mechanical assessment using a neuropin (pinprick) on the chest wall, to discriminate blocked vs unblock areas. |
| Cutaneous distribution mapping | 60 to 90 minutes post-block | Mapping the blocked area (using the previous temperature and mechanical assessments, demarcating lines on the skin) to provide a visual map and, to calculate the area blocked. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Direct visualization of the local anesthetic spread | Immediately post-block | Direct visualization of the local anesthetic spread cephalad and caudad, marking the highest and lowest dermatomes where local anesthetic was still seen on the US, with the US oriented longitudinally. |
| Measurement of the local anesthetic spread in each dermatome with the US | Immediately post-block | Measurement of the local anesthetic spread in each dermatome with the US oriented transversely, by measuring hypoecoic area produced by the presence of local anesthetic. |
Contacts
CONTACTDavid MacLeod, MBBS
CONTACTSara Amaral, MD
Outcome results
None listed