Spinal Anesthesia Explained

What a spinal anaesthetic actually is

Your spinal nerves run inside your lower back, bathed in a clear fluid (cerebrospinal fluid). A spinal anaesthetic places a small dose of local anaesthetic directly into that fluid using a very fine needle. The medicine washes over the nerves and blocks them, so signals of pain, touch and movement can't get through.

The result is fast, dense numbness from about the waist down. Your legs feel heavy and warm, and you won't feel the surgery — even though you may be wide awake. Because the drug is placed right where the nerves are, the dose is tiny compared with a general anaesthetic, and it stays mostly in your lower body. It's one of the most common and well-tested anaesthetic techniques in the world. You can read how it fits alongside other options on our types of anesthesia page.

How it's placed and what you feel

You'll usually sit on the edge of the bed or lie on your side, curled forward to open up the spaces between your spine bones. Curling "like a prawn" and staying still for a minute or two is the most important thing you can do to help.

• The skin is cleaned with a cold antiseptic and numbed with a small stinging injection first.
• Then the fine spinal needle goes in. Most people feel pressure or pushing rather than sharp pain.
• You may feel a brief tingle or a small electric "zing" down one leg — tell the anaesthetist, but it's usually momentary.
• Once the medicine is in, warmth and heaviness spread up your legs within a couple of minutes. Soon you can't lift or feel them.

The whole placement typically takes just a few minutes. The team checks the block is working — often by testing cold or touch on your skin — before surgery starts.

Blood thinners — tell your team before a spinal

This is the one thing it's most important to get right. Because a spinal needle passes close to the spine, if your blood is unable to clot normally there is a small but serious risk of bleeding around the spinal nerves (a haematoma) that, untreated, can damage them. To keep this risk very low, your team needs to know about every blood thinner you take so they can plan the safe timing.

• Tell your anaesthetist about any anticoagulant — for example warfarin, or apixaban, rivaroxaban, edoxaban, dabigatran — and any antiplatelet such as clopidogrel, ticagrelor or prasugrel.
• Mention heparin or low-molecular-weight heparin injections (such as enoxaparin/dalteparin), and even over-the-counter aspirin or fish-oil and herbal supplements.
• These usually need to be stopped for a set number of hours or days before a spinal — and restarted at the right time afterwards. Do not stop or change any of these on your own. Your surgical, anaesthetic or anticoagulation team will give you exact, personalised instructions.

If a safe gap can't be achieved, your anaesthetist may recommend a general anaesthetic instead. The same care applies if you have a bleeding disorder or a low platelet count.

Awake, drowsy, or somewhere in between

With a spinal you can choose, with your anaesthetist, how alert you want to be:

• Fully awake — common for caesareans, so you can meet your baby straight away. A screen keeps the surgery out of view.
• Lightly sedated — a small amount of medicine through your drip makes you relaxed and drowsy, often dozing, while still breathing on your own.

Either way you stay comfortable. You may feel pulling, pressure or movement during the operation — that's normal and not painful, because deep pressure and stretch travel on different, harder-to-block nerve fibres than pain. Tell the team if anything feels sharp; they can top up comfort quickly.

Side effects and risks

A spinal is very safe, but a few effects are common and the team watches for them:

• Low blood pressure — the most frequent effect. As the nerves relax, blood pressure can dip and you may feel briefly sick or light-headed. The team expects this and treats it immediately with fluids and medication, so it's usually short-lived.
• Shivering or feeling cold — common and harmless; warm blankets help.
• Difficulty passing urine — the spinal temporarily blocks the nerves that control your bladder, so you may need a temporary catheter until that sensation and control return.
• Post-dural-puncture headache — uncommon with modern fine needles. It's a headache that's worse sitting or standing and better lying flat, usually appearing within a day or two. It's treatable, so tell the ward team if it happens.
• Itching or mild nausea — possible if a pain-relief medicine is added to the spinal; easily managed.

Serious complications such as nerve damage, bleeding around the spine or infection are very rare. Your anaesthetist will go through the specifics for your operation.

How it wears off and recovery

A spinal fades gradually over a few hours — there's no sudden switch-off. As the block lifts you'll usually notice this order:

• A tingling, pins-and-needles or "fizzy" feeling returns to your feet and legs first.
• You slowly regain the ability to wiggle toes, then bend knees.
• Full sensation and the ability to stand return, typically within 2 to 4 hours of placement, sometimes a little longer.

Because your legs are weak and numb at first, you must stay in bed and call for help before standing — the staff will tell you when it's safe to get up. Bladder sensation can lag behind, so don't worry if it takes a while to pee. If you'd like to track when feeling and movement are likely to come back, our nerve block wear-off timer can give you a rough guide. Many people are pleasantly surprised by how little they hurt for the first few hours, because the numbness lingers.

Spinal versus epidural — what's the difference

People often mix these up because both go into the lower back, but they work differently:

• Spinal — a single one-off injection into the spinal fluid. Fast, dense, complete numbness, but it lasts a fixed time (about 1.5–3 hours) and then wears off.
• Epidural — a thin tube (catheter) is left just outside the spinal fluid, so medicine can be topped up or run continuously for hours or days. Slower to start and often a lighter block, ideal for labour or ongoing post-operative pain relief.

Sometimes both are combined. To compare in detail, see our epidural anesthesia explainer. Your anaesthetist picks whichever suits your operation and how long pain relief is needed.

Spinal vs epidural at a glance