Spinal anesthesia is widely performed using a surface landmark based 'blind' technique. Multiple passes and attempts while administering spinal anesthesia are associated with a greater incidence of post dural-puncture headache, paraesthesia and spinal hematoma.~Real time and pre-procedural neuraxial ultrasound techniques have been used to improve the success rate of spinal anesthesia. The use of real time ultrasound-guided spinal anesthesia has to date been limited to case series and case reports. Its use may be limited by the requirement for wide bore needles and the technical difficulties associated with simultaneous ultrasound scanning and needle advancement. The use of pre-procedural ultrasound has been shown to increase the first pass success rate for spinal anesthesia only in patients with difficult surface anatomic landmarks.No technique has been shown to improve the success rate of dural puncture when applied routinely to all patients.~Studies on pre-procedural ultrasound-guided spinal techniques are limited to a midline approach using a transverse median view (TM). The parasagittal oblique (PSO) view consistently offers better ultrasound view of the neuraxis compared to TM views. However no studies have been conducted to assess whether these superior PSO views translate into easier paramedian needle insertion.~We hypothesised that the routine use of pre-procedural ultrasound-guided paramedian spinal technique results in less number of passes required to enter the subarachnoid space when compared to the conventional landmark based midline approach.
Multiple passes and attempts while administering spinal anesthesia are associated with a greater incidence of post dural-puncture headache, paraesthesia and spinal hematoma. The investigators hypothesised that the routine use of pre-procedural ultrasound-guided paramedian spinals reduces the number of passes required to achieve enter the subarachnoid space when compared to the conventional landmark-guided midline approach.