Expert: Dr Ian Jackson - please note UK based - 9/11/2007

Question
My daughter is having a ceaseran and the doctor has decided to do a spinal tap instead of an epidural.  What is the difference?

Answer
Hi there

Spinals are slightly different to epidurals. Basically an epidural involves putting a little tube into the epidural space in your back - this space lies outside the dura membrane and this gives it its name. Local anaesthetic is passed down the catheter into the epidural space and this numbs the nerves as they pass through this space to get to your legs, tummy etc. The dose required to allow for the operation is somewhere around 20-30 mls of local anaesthetic and this takes about 20-30 minutes to work
A spinal uses a thinner needle which is passed through the epidural space and then in through the dural membrane into the CSF (cerebrospinal fluid) that lies inside it. The anaesthetist then injects a much smaller amount of local anaesthetic into this fluid and it numbs the nerves there. The main differences apart from what I have explained is that the spinal is usually technically easier, works faster, provides a stronger block, uses much less local anaesthetic and is a single shot technique. So it uses around 2-3 mls of the same strength local anesthetic and works within 5-10 minutes.
Hope this helps a bit.
Dr Ian Jackson