Shoulder Replacement Anaesthesia: The General Anaesthetic and Interscalene Nerve Block

A shoulder replacement is almost always done under a general anaesthetic, so you are asleep for the operation, usually combined with a regional nerve block (an interscalene block) that numbs the whole arm and carries most of the pain relief for the first day.¹ A few centres now offer the operation awake under the block alone, but for most primary replacements the general-plus-block combination is the standard arrangement.

When I had my reverse replacement I assumed anaesthesia meant one decision: asleep or not. It turned out to be two things working together, and the block was the part nobody had prepared me for. This is the plain version I wanted beforehand. If you want the wider picture of the day itself, read the shoulder replacement procedure; for the operation as a whole, start with the shoulder replacement guide.

What anaesthetic is used for a shoulder replacement?

The usual arrangement is a general anaesthetic combined with an interscalene nerve block: the general anaesthetic keeps you asleep and still for the roughly 1.5 to 2 hours a primary replacement takes, and the block numbs the arm so you wake with the shoulder already pain-free.¹ The two are not rivals; pairing them lets the anaesthetist run a lighter general anaesthetic and hand you over to recovery with the pain already covered rather than chasing it afterwards.

The reason the block earns its place is measurable. Reviews of interscalene blocks for shoulder surgery report lower pain scores and less opioid use in the first day compared with a general anaesthetic on its own, which is why it has become the default regional technique for this operation². My anaesthetist described it as doing the heavy lifting on pain while I slept through the surgery itself.

What is an interscalene nerve block?

An interscalene block is an injection of local anaesthetic placed around the brachial plexus, the bundle of nerves in the lower neck that carries all the sensation and movement of the arm, guided by ultrasound so the anaesthetist can watch the needle and the nerves on screen.³ Within about half an hour the shoulder and arm go numb, heavy and hard to move, which is exactly the point⁴.

A nerve block is not the same as being put to sleep: it switches off one region of the body while the rest of you carries on³. For the shoulder it is the gold-standard regional method precisely because that one region is the whole surgical field. It can be given as a single injection or, less commonly, through a fine catheter left in place to top the numbness up over a day or two.

Can you be awake for a shoulder replacement?

Yes, in some centres the operation can be done awake under the interscalene block alone with light sedation, so you feel no pain but are not put to sleep, and once the arm is numb enough the surgeon starts.⁴ The draw is avoiding the general anaesthetic altogether: no sore throat from a breathing tube, less nausea and grogginess afterwards, an earlier drink and meal, and sometimes an earlier trip home.

It is not the right choice for everyone, and it is a conversation to have rather than a box to tick. The anaesthetist weighs your breathing reserve, your general health, and whether you would genuinely rather be aware in theatre. Comparable studies in reverse replacements have found the block with sedation to be a safe and cost-effective way to run the operation in suitable patients⁵. If it appeals, it belongs on your list in questions to ask before a shoulder replacement.

What the block actually feels like

The strangest part of the whole operation for me was not the surgery but waking to an arm I could not feel at all: heavy, warm, and so completely dead that a nurse had to tell me it was mine before I believed her. It sat across my chest like a sandbag, and for the best part of a day it belonged to someone else.

Nobody had described that to me, and I want to say it plainly because it can be unnerving if it lands as a surprise. The heaviness is the block working, not a complication, and the sensation and movement come back gradually as it wears off. The instruction that mattered was to protect the numb arm and not let it hang or catch, because you cannot feel it warning you⁴. I have written the rest of those first strange hours in my shoulder replacement recovery.

The side effects and risks

Most effects of the block are temporary and expected: a hoarse voice, a droopy eyelid on the same side, the warm numb arm, and one half of the diaphragm resting for a few hours, which people with good lungs barely notice.⁴ The diaphragm point is the one that shapes the decision, because someone with poor breathing reserve feels it far more, which is part of why the anaesthetist reviews your chest before settling the plan².

Lasting nerve injury from the block is rare, and the general anaesthetic carries its own familiar and mostly minor after-effects: a sore throat, nausea, and drowsiness, with serious complications uncommon⁴. Blood clots are rarer after shoulder surgery than after hip or knee surgery. None of this is unique to the anaesthetic, and it sits alongside the wider picture in shoulder replacement risks and complications.

When the block wears off, and the pain afterwards

A single-injection block typically keeps the arm numb and pain-free well into the first day, commonly around 12 to 24 hours, and then wears off, sometimes with a sharp rebound of pain as the sensation floods back.² For me it arrived in the small hours, which is apparently the usual timing, and it was the one genuinely rough night of the recovery.

The ward manages this by starting your regular pain relief before the numbness goes rather than waiting for the pain to announce itself, so the tablets are already working as the block fades². Where a longer stretch of numbness is wanted, a continuous catheter block can carry the relief further into the recovery⁵. Knowing the rebound is coming is half the battle, and the days that follow settle into a steadier rhythm.

Getting ready: the pre-assessment

Before the day, a pre-operative assessment checks that you are fit for the anaesthetic, because general health and fitness matter as much for the anaesthetic as for the surgery.¹ It is the point where the plan is actually decided: general anaesthetic with a block, or, in the right centre and the right patient, an awake block with sedation.

Come to it with questions rather than assumptions. It is worth asking whether they use a nerve block routinely, whether an awake option is on the table for you, and what the plan is for pain relief when the block wears off, since the answers vary between anaesthetists and hospitals⁴. Those belong on the same list as the surgical ones you take to the consultation.