Ultrasound assisted neuraxial blockade in obstetric anesthesia

Central neuraxial blocks (CNBs) relevant to the practice of obstetric anesthesia and analgesia are spinal, epidural and combined spinal-epidural injections. These techniques are routinely used for cesarean deliveries and labor pain relief. Traditionally, CNBs are performed using surface anatomical landmarks. In the first instance the highest point of each iliac crest is identifies. The imaginary line connecting these points allegedly passes through the L4 vertebral body in non-pregnant women, and L3 vertebral body in pregnant women [1]. Based on this, the operator palpates and counts the spinous processes and decides on the needle entry point. Although this technique is widely accepted as relatively reliable, the correlation is inconsistent even in non complicated cases. Obesity, tissue edema, pelvic rotation, limited ability to bend forward, hyperlordosis, labor pain, underlying spinal deformity or previous back surgery and instrumentation pose additional difficulty for anesthesiologists to correctly locate the intervertebral levels.