"Ultrasound vs. Landmark Technique for Spinal Anesthesia in Obese Women Undergoing Cesarean Section"

This clinical trial is designed to compare two techniques for performing subarachnoid block (SAB) in obese women undergoing elective cesarean sections. The study aims to evaluate the effectiveness and safety of ultrasound-assisted spinal anesthesia versus the traditional landmark-guided technique. Both techniques are commonly used for regional anesthesia, but the effectiveness of ultrasound assistance in improving procedural accuracy, reducing complications, and enhancing the overall success rate in obese parturient has not been sufficiently studied.

Study Design

This is a randomized controlled trial conducted at the Obstetric Operating Theatre of Bangladesh Medical University (BMU). Participants will be randomly assigned to one of two groups: Group A (landmark technique) and Group B (ultrasound-assisted technique). The study will evaluate the following:

Primary Objective:

To assess the number of needle attempts required for successful subarachnoid block in both groups.

Secondary Objectives:

To evaluate the procedure time, incidence of post-dural puncture headache (PDPH), chronic low back pain at the needle insertion site, and quality of life related to pain.

Interventions

Both groups will receive the same local anesthetic agents for the SAB: 0.5% hyperbaric bupivacaine with 25 μg fentanyl. The techniques will differ in how the intervertebral space is located.

Group A (Landmark Technique): In this technique, the L3-L4 or L4-L5 intervertebral spaces will be identified using the traditional landmark method. The anesthesiologist will palpate the iliac crests to find Tuffier's line and will estimate the intervertebral space based on these bony landmarks.

Group B (Ultrasound-Assisted Technique): In this group, ultrasound guidance will be used to locate the intervertebral space. A low-frequency (2-5 MHz) curvilinear probe will be employed to visualize the lumbar spine. The procedure will include scanning the area to identify the midline, the interlaminar spaces, and the depth of the epidural and spinal spaces, ensuring that the correct intervertebral level is identified before needle insertion.

Randomization

Participants will be randomly assigned to one of the two intervention groups using Block randomization schedule. This will ensure that both groups are comparable at baseline and that the results are unbiased.

Procedure

Before the procedure, participants will undergo routine preoperative assessment, including fasting for 6 hours, intravenous line establishment, and monitoring. They will be positioned in a sitting position with a pillow for lumbar flexion. After preparing the skin with aseptic techniques, the spinal needle will be inserted according to the assigned technique.

In Group A, after identifying the L3-L4 or L4-L5 intervertebral space using the landmark technique, the anesthesiologist will administer the Subarachnoid Block (SAB). In Group B, ultrasound will be used to precisely identify the lumbar intervertebral spaces before needle insertion.

Follow-Up

Participants will be monitored for immediate postoperative complications, including Postdural puncture headache (PDPH), and will be assessed for chronic low back pain at the needle insertion after 3 months over phone. Additionally, the quality of life related to low back pain will be evaluated via phone interviews.

Expected Outcomes

The primary hypothesis is that the ultrasound-assisted technique will result in fewer needle attempts and a more accurate identification of the intervertebral space compared to the traditional landmark technique. Additionally, investigators expect to find that ultrasound assistance reduces the incidence of Postdural puncture headache (PDPH) and chronic low back pain, thereby improving the patient's overall quality of life postoperatively.

This trial will provide valuable insights into the effectiveness of ultrasound in improving the safety and accuracy of Subarachnoid Block (SAB) in obese parturient, potentially changing the standard of care in obstetric anesthesia for this patient population.

Inclusion criteria

• Elective caesarean section
• ASA physical status: Ⅱ
• Obese parturient (BMI ≥ 30.1 kg/m²)

Exclusion criteria

• Allergic to local anaesthetic (0.5% Bupivacaine hydrochloride with 8% Dextrose and 2 % Lidocaine hydrochloride USP)
• Preexisting neurological deficit by clinical examination
• Any contraindication to SAB
• History of scoliosis or spinal instrumentation
• Allergy to ultrasound transmission gel