Spinal vs Epidural

Three types, not two

The Obstetric Anaesthetists' Association describes three kinds of regional anaesthetic used in maternity care, not two: a spinal, an epidural, and a combined spinal-epidural. All three involve an injection of local anaesthetic into your back, and in all three "you remain awake and comfortable during the birth".

The difference is where the medicine goes and whether anything is left behind.

The spinal

The OAA describes it as "an injection of local anaesthetic into the lower back to numb the lower half of your body". The nerves carrying feeling from your lower body sit in a sac of fluid; a fine needle puts the anaesthetic directly into that fluid. Nothing stays in your back afterwards. It "works quickly and you stay awake, but won't feel pain from the waist down".

The epidural

Here the anaesthetist places "a thin tube near the nerves in your back to deliver pain relief". ACOG describes the same sequence from the other side of the Atlantic: a needle goes in, "a thin tube is usually inserted through it, and then the needle is withdrawn. The tube stays behind, and medication then can be given as needed through the tube."

Because the tube stays, the dose can be topped up for as long as you need it. That is the whole point of it in labour.

The combined spinal-epidural

Both at once. The OAA: "The spinal anaesthetic makes you go numb quickly. The epidural gives more anaesthetic, if needed."

Why a caesarean usually means a spinal

The OAA states plainly that a spinal "is the most common type used for a caesarean birth". Speed and density are the reasons: an operation needs a block deep enough that a surgeon can open your abdomen, and it needs it within minutes rather than over an hour.

An epidural already sited for labour can be converted. The OAA notes that for a caesarean birth, "a stronger dose can be given through the tube to fully numb the lower body". That is why a woman who has laboured with an epidural and then needs an unplanned caesarean is often not given a fresh injection — the access is already there.

NICE is explicit about which family of anaesthetic should be offered first for a caesarean: "offer women who are having a caesarean birth regional anaesthesia in preference to general anaesthesia". NICE also asks that anaesthesia be induced in theatre rather than beforehand.

What it actually feels like going in

The OAA describes the sequence. You sit up or lie on your side and curl over your bump. The anaesthetist feels the spaces in your back, then numbs the skin with local anaesthetic. "From this point, most people just feel some pushing in their back." Tingling or pain should be reported, because it helps the anaesthetist find the right space.

The OAA says the procedure "usually only takes a few minutes", though it "may take longer if it is difficult to find the small space in your back". The onset is described in stages: your skin feels warm, then pins and needles, then numbness to touch, then legs that are heavy and hard to move.

An epidural sited for labour is slower to arrive at full effect. The OAA's figures are that an epidural "takes about 20 minutes to set up and up to 30 minutes before you feel the full effect".

How they check it has worked

For a caesarean the block is formally tested. The OAA: the anaesthetist will ask you to lift your legs and touch your skin "with something soft, sharp or cold", asking what you can feel. The HSE describes the same check in Irish units, often with a cold spray moved down the body — "if the spray feels cold, the anaesthetic may need more time to work. You may be given slightly more anaesthetic."

The OAA is clear about the threshold: the anaesthetist "will only allow the obstetrician to start the caesarean birth when they are satisfied the anaesthetic is fully working".

On what you will still notice, the OAA does not oversell it: "You shouldn't feel any pain during the operation but it is normal to feel pressure and pulling. Some people describe it as 'feeling like someone is doing the washing-up' in their tummy."

The things that come with it

A regional anaesthetic for a caesarean brings a cannula in your hand or arm, monitors for blood pressure, heart rate and oxygen, and a urinary catheter. The OAA explains why the catheter is there: "to keep your bladder empty during the operation. This stays in until the heaviness in your legs wears off so you don't need to worry about getting to the toilet." NICE puts the same thing as a recommendation to clinicians: give an indwelling catheter to prevent over-distension of the bladder.

An epidural in labour brings a different set of consequences — more monitoring, and pain relief that can be adjusted over hours rather than being a single event.

What the anaesthetists say about safety

The OAA states that spinals and epidurals "are usually safer for you and your baby" than a general anaesthetic for a caesarean, and that you and your partner can share the birth. On epidurals in labour specifically, the OAA's summary of the evidence is that they do not make a caesarean more likely, do not make forceps or ventouse more likely, do not make your baby drowsy or cause long-term harm, and do not cause back pain after childbirth.

None of that makes either one compulsory. Both are offers.

What you can ask

You can ask which type is planned for you and why, whether an existing epidural will be topped up or replaced, and what the plan is if the block is not adequate when tested. You can ask the anaesthetist to tell you before each step. You can decline any of it, and NICE's expectation of maternity teams is that you are supported to "accept or decline care that is offered" and to change your mind.