Spinal anaesthesia has the advantag

Spinal anaesthesia has the advantage that profound nerve
block can be produced in lower half of the body by the relatively
simple injection of a small amount of local anaesthetic.
However, the greatest challenge in spinal anaesthesia is to control
the spread of local anaesthetic through the cerebrospinal
fluid (CSF) to provide a block which is adequate for the proposed
surgery without unnecessary extensive spread, and increased
risk of complications [5].