Epidural
With an epidural, the epidural needle is inserted only as far as the epidural space. This space is located just outside a layer of tissue called the 'dura mater'. The dura mater tissue encases the spinal cord and spinal fluid.
Once the needle is believed to be in the correct location, a fine, flexible, hollow tube or 'catheter' (about the width of fishing line) is passed through the hollow needle, so that the end of the tube rests in the epidural space. The epidural needle is then removed and the catheter is left in place. The catheter is about 90cm long and the remainder of the tube is eventually taped in place, up the length of the woman's back.
The anaesthetic medication(s) chosen by the anaesthetist are then injected down the catheter to 'bathe' the nerves that lead to the woman's uterus and lower body, to numb them for the operation. The full effect of the medications will take about 10 to 30 minutes.
After the Caesarean, once the initial dose of medication has worn off (about 1 to 2 hours), pain-relieving medications (such as the narcotic Pethidine) can be administered down the epidural catheter for post-operative pain relief. This is usually continued for about 24 to 48 hours after the operation.
Spinal
With a spinal anaesthetic, the spinal needle is inserted a little further than the epidural space. The end of the needle actually pierces the 'dura mater' layer of tissue (the dura mater being the tissue that encases the spinal cord and spinal fluid). The end of the needle reaches the cerebral spinal fluid, or 'CSF' (the pool of fluid that surrounds the spinal cord and flows around the brain). The initial procedure is similar to a
spinal tap, except that the spinal fluid is not removed.
Image 8-24 shows the spinal needle being inserted as far as the spinal fluid, and the epidural needle inserting the epidural catheter.