Comparison of efficacy of ultrasound guided and conventional landmark technique in patients with difficult spine predictors for spinal anesthesia: open RCT

Neuraxial procedures are traditionally blind techniques where space is identified by palpation of anatomic landmarks namely iliac crests and spinous processes together with tactile feedback during needle  insertion and loss of resistance confirming entry into subarachnoid space. But the technical difficulty of neuraxial blockade correlates with the quality of palpable surface landmarks. Palpation is often inaccurate and these surface landmarks may be absent, indistinct or distorted in many adult patients because of obesity, previous spinal surgery, deformity or degenerative changes of aging, insufficient gap between the spinal vertebrae, skin distances from the subarachnoid space, size of the needles; therefore, failed blocks and complications are common.

Repeated attempts and redirections of the needle may lead to nerve injury, spinal hematoma, post dural puncture headache and added discomfort to the patient. Multiple case reports demonstrate the utility of ultrasound in guiding neuraxial blockade in patients with difficult spinal anatomy. Ultrasound imaging provides information about the accurate intervertebral level of puncture, optimal needle insertion point and depth of needle advancement for a successful neuraxial block. But there has been only few RCTs in the Indian scenario on the subject. Therefore, we designed a study aimed to compare the efficacy between the preprocedural ultrasound assisted technique and the conventional landmark based technique in patients with predictors of difficult spinal posted for elective surgery under spinal anesthesia.