Ultrasonography Versus Palpation for Spinal Anesthesia in Obese Parturients Undergoing Cesarean Delivery

Ultrasonography of the lumbar spines using an 8-2 MHz curved array transducer. Identification of the intervertebral space with the best image. Marking the patient's skin with horizontal and vertical lines over the L3-L4 and L2-L3 intervertebral spaces.

Moving the ultrasound probe on the patient's back with the machine in the freeze position.

Conventional palpation of the anatomical landmarks. The line crossing the iliac crests (Tuffier line) is assumed to cross the spine at L4 spinous process or L3-L4 intervertebral space. Identification of the widest intervertebral space. Marking the patient's skin with horizontal and vertical lines over the L3-L4 and L2-L3 intervertebral spaces.

Spinal anesthesia using a 25- or 22-gauge spinal needle

Bupivacaine 12.5 mg (2.5 mL 0.5%) will be administered in the subarachnoid space

Fentanyl 15 μg will be administered in the subarachnoid space