Spinal anaesthetic can be administered when operations below the waist are being performed. The patient remains awake, but is often sedated, while an anaesthetist or surgeon places a needle into the lower back.
The needle is inserted between the vertebrae so that the tip enters the spinal canal, which contains cerebrospinal fluid and surrounds the spinal cord. The spinal cord carries all the nerve messages to and from the brain, and runs through the centre of the 24 vertebrae that form the backbone.
A small amount of anaesthetic is injected into the spinal canal, so that the nerves below the level of injection no longer work and pain from the operation cannot be felt. The patient is often tilted slightly to prevent the anaesthetic from flowing further up the spine and affecting nerves above the level required for adequate anaesthesia.
The side effects of a spinal anaesthetic include low blood pressure, a headache for several days, and a slow heart rate. Nausea and vomiting are less common complications.
This type of anaesthetic is usually given when the patient is not well enough to stand a general anaesthetic, for Caesarean sections, and in other circumstances when it is desirable for the patient to be awake.