A spinal anaesthetic is an alternative to a general anaesthetic for some operations. It allows the patient to stay awake during the operation without feeling any pain.
What is a spinal anaesthetic?
For many operations a general anaesthetic (GA) will be required. This is where the anaesthetist gives the patient medication, usually through a drip (cannula) into a vein, and sends them off to sleep. This keeps the patient unconscious, still and pain-free for the duration of the operation. A breathing tube is inserted after the patient is asleep so the breathing can be controlled throughout the operation. When the operation is finished the anaesthetist allows the patient to wake up.
An alternative to a general anaesthetic is a spinal anaesthetic. A spinal anaesthetic can be used for most operations below the waist. A spinal anaesthetic is performed by an anaesthetist. A very fine needle is inserted into the middle of the lower back and local anaesthetic is injected through the needle into the fluid that surrounds the spinal cord. The local anaesthetic numbs the nerves that supply the tummy, hips, bottom and legs. Once the nerves are completely numb you will not feel any pain from an operation and you will also not be able to move your legs. Other medications can also be injected which provide excellent pain relief for several hours after the operation.
What operations may be performed under spinal anaesthetic?
- Urology - prostate, bladder or genital operations.
- Orthopaedic - operations on the bones in the hips, legs and feet.
- Gynaecology - operations on the womb (uterus), vagina or ovaries.
- Vascular - operations on the blood vessels in the legs.
- General - groin hernias and piles.
- Obstetrics - caesarean section.
Do I have different options when having a spinal anaesthetic?
A spinal anaesthetic alone
With this option you would be awake during the operation and be able to hear what is going on in the operating theatre but NOT BE ABLE TO FEEL ANY PAIN. You may, however, have a sensation of movement or pressure - this is entirely normal. A screen will put up so that you will not be able to see the operation. If you are choosing this option it might be useful to bring some music and headphones with you so that you can listen to it during the operation.
A spinal anaesthetic with sedation
In this instance, once the spinal anaesthetic has been performed and the anaesthetist is happy with the block (see later for details) the anaesthetist will give some medication into your drip to make you feel relaxed and sleepy. This is NOT a full general anaesthetic and you may, from time to time, be aware of voices and other general theatre activity but you will NOT FEEL ANY PAIN.
A spinal anaesthetic and a general anaesthetic combined
In some situations the anaesthetist might feel that a combination of a spinal anaesthetic and a general anaesthetic is the best option for you. Also in some situations (for example, if the operation takes an unexpectedly long time or you start to feel discomfort during the operation) it might be necessary to add in a general anaesthetic to overcome these issues.
Your anaesthetist will see you before the operation to discuss all the options with you. They will help you come to a decision as to what the best option is for you.
How is the spinal anaesthetic given?
The spinal anaesthetic will be performed in the anaesthetic room or in theatre.
There will be an operating department practitioner to assist the anaesthetist and another member of the theatre team to support and help you during the procedure.
Before the spinal anaesthetic is given, the anaesthetist will put a drip (cannula) in your hand and you will be attached to a monitor (ECG, blood pressure and oxygen saturations).
Most often the spinal anaesthetic will be done whilst you are awake. Your anaesthetist will instruct you as to what position you need to get into for the procedure to be done. This will be in one of two positions:
- In a sitting position with you slumped forward, chin on your chest, shoulders down and bottom curled under.
- Lying on your side with your knees curled up towards your chest.
These positions help to open up the spaces between the bones in your back, which is where the anaesthetist needs to put the spinal anaesthetic.
Once you are in the correct position your back will be cleaned with antiseptic, the anaesthetist will scrub their hands and put on a surgical gown, gloves, hat and mask. These steps help to minimise the risk of infection.
The anaesthetist will feel your back quite firmly to identify certain landmarks and identify where exactly the spinal anaesthetic needs to be inserted.
Local anaesthetic will firstly be injected to numb the skin; then the fine spinal needle will be inserted.
At this point it is particularly important to keep very still. You should not feel significant pain; however, if the needle goes close to one of the nerves that supply your legs you may feel a shooting pain down one of your legs.
If this occurs it is important that you keep still and let your anaesthetist know, telling them which leg you felt the pain in.
Once the medication has been injected you will feel a warm tingly sensation in your bottom and your legs start to go numb.
The spinal anaesthetic doesn't work instantly; it takes a little time to work - approximately 5-15 minutes. You will also start to feel that it is difficult to move your legs, and eventually not be able to move your legs at all.
How do they test the block?
Your anaesthetist will need to check the level (how far up the body) and quality of the block.
In order to do this you will be asked if you can lift your legs off the bed - they should feel very heavy or you may not be able to move them at all.
The anaesthetist may then use cold spray to check the level of the block. They will spray ice-cold spray on to your legs and tummy.
Where the spinal anaesthetic is working well you will not be able to feel the cold (you may still feel the 'blow' of air if an aerosol can is used). When you feel the ice cold, this means that the spinal anaesthetic stops at that point.
Your anaesthetist may also check the block, using a pinprick or gentle touch. Once the anaesthetist is happy that your spinal anaesthetic is ready, your operation can start.
What happens after a spinal anaesthetic?
After a period of time the effect of the spinal anaesthetic will wear off. You will gradually start to be able to feel and move your legs. You may experience tingling or pins and needles in your legs as the spinal anaesthetic wears off.
The length of time that the spinal anaesthetic takes to wear off will depend on the medications that the anaesthetist uses for the spinal anaesthetic. Usually the block will have worn off in four hours and you will be able to get out of bed six hours after the spinal anaesthetic.
Often the anaesthetist will add pain-killing medication to the spinal anaesthetic to give pain relief after the operation. These effects last after the feeling and movement have returned in your legs.
What are the advantages of a spinal anaesthetic?
There are some medical conditions that make having a general anaesthetic (GA) more risky - for example, significant breathing problems. Your anaesthetist will discuss the options with you and help you to decide which option is best suited to your particular situation. The following are the advantages of having a spinal anaesthetic:
- Less risk of getting a chest infection after the operation.
- No detrimental effect on the lungs and breathing.
- Excellent pain relief immediately after the operation.
- Reduced need for strong painkillers which can cause a feeling of sickness (nausea), being sick (vomiting), confusion and constipation.
- No 'hangover' effect from the GA.
- Less risk of confusion after the operation, especially in elderly patients.
- Less nausea or vomiting, which can be caused by the GA medications.
- Being able to eat and drink sooner after the operation.
What are the side-effects and complications of spinal anaesthetic?
Some of the medicines that are put in the spinal anaesthetic can make you itch.
The spinal anaesthetic can cause your blood pressure to drop. If this happens, your anaesthetist will give fluid into your drip and medicine to increase your blood pressure.
You might find that you find it difficult to pass urine. This happens especially in men. If this happens you might need a urinary catheter until the spinal anaesthetic has worn off completely and your bladder function returns to normal.
You might get a particularly bad headache that is caused by the spinal anaesthetic. This happens in 1 in 200 to 1 in 300 spinal anaesthetics given for young women giving birth but it is much less likely in an older person. This headache feels different to normal headaches in that it gets worse when you sit/stand up and better when you lie down. Normally this type of headache resolves with rest, drinking plenty of fluids and taking simple painkillers. Very occasionally you may require another procedure similar to the initial spinal anaesthetic to resolve the headache. If you get a bad headache after you have been discharged home it is important that you see your GP or attend hospital as you will need to be reviewed by an anaesthetist.
Occurring very rarely
A high block - very occasionally the spinal anaesthetic can affect higher up the body than is needed for the operation. In this situation you may experience weakness of your arms and, in very rare situations, difficulty in breathing. If this occurs your anaesthetist will explain to you what is happening and assist your breathing until the spinal anaesthetic wears off.
Nerve damage. This is the complication that patients understandably worry most about. The risk of permanent nerve damage is extremely rare - about 1 in 50,000. The risk of temporary loss of sensation, pins and needles and sometimes muscle weakness is higher but usually resolves in a few days to weeks.
Further reading and references
; Royal College of Anaesthetists, February 2017
; Royal College of Anaesthetists, last updated February 2017
; The 3rd National Audit Project of the Royal College of Anaesthetists (NAP3), 2009