The classical method for spinal anesthesia relies on the use of bony landmarks to identify
the level and point of entry of the spinal needle. Over the years, in experienced hands, this
method consistently proved to be successful and safe.
The introduction of ultrasound to guide neuraxial anaesthesia into clinical practice was
relatively slow compared to peripheral nerve blocks or central venous catheterization. This
could be due to the technical difficulties posed by the bony structures surrounding the
spinal cord and its dura that blocks the path of the ultrasound beam. Many anesthetists are
reluctant to change their conventional landmark technique, particularly with most studies
showing no change in the success rate between ultrasound guided and the landmark techniques.
Several studies however showed that the ultrasound guided approach reduces the number of
attempts to achieve a successful block and reduces the procedure time particularly in obese
patients and those with technical difficulties.
In this study the investigators are trying to answer the following question : Is there any
advantage in using ultrasound to guide spinal anaesthesia in non obese obstetric patients
with easily palpable bony landmarks?