General anaesthesia has several side effects and risks. Where possible, it is desirable to keep the patient awake and only anaesthetise the area required for the operation. Generally, this leads to better pain relief, fewer medication side effects and a smoother recovery.
Peripheral Nerve Blocks
Peripheral nerve blocks are a type of regional anaesthesia. The patient remains awake during the procedure. A local anaesthetic is injected around specific nerves, causing the area distal to the nerves to be anaesthetised. This usually involves making a limb numb so that a surgeon can operate without causing any pain. A screen is put up between the patient and the operating site so that they cannot see the operation taking place.
The injection is performed under ultrasound guidance, sometimes with the help of a nerve stimulator, so that it can be accurately applied to the area around the targeted nerve.
Regional anaesthesia will be performed where there are facilities available to quickly induce a general anaesthetic if it is not effective or the patient starts to experience pain. Patients are closely monitored. Sedation may be given to help the patient relax.
Sometimes a patient may have a combination of regional and general anaesthesia to reduce the physiological response during surgery and improve pain management post-operatively.
Central Neuraxial Anaesthesia
Central neuraxial anaesthesia is also known as a spinal anaesthetic or spinal block. It is a type of regional anaesthesia. The most common examples of when it is used for:
- Caesarean sections
- Transurethral resection of the prostate (TURP)
- Hip fracture repairs
The patient remains awake during the procedure. A local anaesthetic is injected into the cerebrospinal fluid, within the subarachnoid space. It is only used in the lumbar spine, after the point where the spinal cord ends, to avoid damaging the spinal cord. In practice, the needle is usually inserted into the L3/4 or L4/5 spaces.
Neuraxial anaesthesia will cause numbness and paralysis of the areas innervated by the spinal nerves below the level of the injection. Cold spray applied to the skin is often used to test whether the anaesthetic has worked. It takes around 1-3 hours for the anaesthetic to wear off.
Epidural anaesthesia is most commonly used for analgesia in pregnant women in labour and post-operatively after a laparotomy (open abdominal surgery). Importantly, an epidural is different from a neuraxial/spinal block.
An epidural involves inserting a small tube (catheter) into the epidural space in the lower back. This is outside the dura mater, separate from the spinal cord and CSF. Local anaesthetic medications are infused through the catheter into the epidural space, where they diffuse to the surrounding tissues and through to the spinal cord, where they have an analgesic effect. This offers good pain relief during labour. Levobupivacaine is often used, with or without fentanyl.
- Headache if the dura is punctured, creating a hole for CSF to leak from (“dural tap”)
- Motor weakness in the legs
- Nerve damage (rare)
- Haematoma (may cause spinal cord compression)
When used for analgesia in labour, the risks include:
- Prolonged second stage
- Increased probability of instrumental delivery
Patients need an urgent anaesthetic review if they develop significant motor weakness (unable to straight leg raise). The catheter may be incorrectly sited in the subarachnoid space (and cerebrospinal fluid) rather than the epidural space.
Local anaesthesia is used to numb a very specific area where a procedure is being performed. The local anaesthetic (e.g., lidocaine) is usually injected by the person performing the procedure (rather than involving an anaesthetist). This is usually used for smaller operations and procedures.
Common examples of procedures performed using a local anaesthetic are:
- Skin sutures in A&E after a skin laceration
- Minor surgery to remove skin lesions
- Dental procedures
- Hand surgery (e.g., carpal tunnel syndrome surgery)
- Performing a lumbar puncture
- Inserting a central line
- Percutaneous procedures (e.g., percutaneous coronary intervention)
Last updated August 2021