Nerve Block — How It Works, Benefits & Recovery — Procedure Guide, Recovery & Risks | MyMedicPlus

A nerve block is a targeted injection of a local anaesthetic agent — and sometimes a corticosteroid — adjacent to a specific peripheral nerve, nerve plexus, or spinal nerve root to produce temporary interruption of pain signal transmission, achieving anaesthesia or analgesia in the anatomical territory served by that nerve. Nerve blocks are used in two distinct clinical contexts: as regional anaesthesia techniques that allow surgery to be performed without general anaesthesia; and as therapeutic pain interventions for the management of acute and chronic pain conditions. The development of high-resolution portable ultrasound technology has transformed nerve block practice: real-time ultrasound guidance allows direct visualisation of the target nerve, surrounding vascular structures, fascial planes, and adjacent organs during needle placement, dramatically improving accuracy, success rates, and safety compared with the older landmark-based or nerve stimulator techniques. The anatomical precision of ultrasound guidance has expanded the range of accessible nerve targets, reduced complications including intravascular injection and nerve injury, and enabled the use of lower volumes of local anaesthetic (hydrolocation technique) with equivalent efficacy. Two categories of nerve block exist by duration: single-shot blocks using a single injection of long-acting local anaesthetic (bupivacaine 0.5%, ropivacaine 0.5–0.75%) providing 8–24 hours of analgesia; and continuous nerve block techniques in which a fine catheter is placed adjacent to the nerve through which a dilute local anaesthetic solution is infused via a portable pump, providing sustained analgesia for 2–5 days — a particularly valuable technique for post-operative pain management after major orthopaedic, thoracic, and breast surgery, enabling opioid-free or opioid-minimising pain control during the critical early post-operative period.

Nerve blocks are indicated in both surgical and non-surgical (chronic pain) settings across a wide spectrum of clinical presentations. In the perioperative surgical setting, nerve blocks provide the primary anaesthetic or supplementary analgesia for: upper limb surgery — shoulder arthroplasty and arthroscopy (interscalene brachial plexus block), forearm and hand surgery (supraclavicular, infraclavicular, or axillary brachial plexus block); lower limb surgery — total hip and knee arthroplasty (femoral, adductor canal, obturator, IPACK, and pericapsular nerve group blocks), ankle and foot surgery (popliteal sciatic and ankle blocks), anterior cruciate ligament repair (adductor canal block); abdominal surgery — laparotomy (transversus abdominis plane or TAP block, epidural), laparoscopic procedures (bilateral TAP or quadratus lumborum blocks); thoracic surgery and rib fracture analgesia (thoracic paravertebral, erector spinae plane, or serratus anterior plane blocks); breast surgery (PECS I and II, serratus anterior blocks); and paediatric surgery across all regions. In the chronic pain management context, nerve blocks treat: chronic low back pain from facet joint arthropathy (medial branch blocks — diagnostic and therapeutic, with radiofrequency ablation for sustained relief); lumbar radiculopathy and spinal stenosis (lumbar epidural steroid injections); cervicogenic headache and occipital neuralgia (greater and lesser occipital nerve blocks); complex regional pain syndrome (CRPS) — sympathetic nerve blocks (lumbar sympathetic chain, stellate ganglion); post-herpetic neuralgia and trigeminal neuralgia; cancer pain (coeliac plexus block for pancreatic cancer pain, superior hypogastric plexus block for pelvic cancer pain); and chronic migraine (occipital nerve blocks as part of a multimodal approach). Contraindications include: patient refusal or inability to cooperate; confirmed allergy to the specific local anaesthetic agent; active infection or cellulitis at the injection site; and uncorrected coagulopathy or therapeutic anticoagulation for deep or neuraxial blocks — anticoagulant management protocols (ASRA/ESRA bridging guidelines) define safe windows for block performance around anticoagulant dosing.

The patient is positioned to optimise access to the target nerve or nerve plexus — supine, lateral, prone, or sitting depending on the specific block. Standard aseptic technique is used: the skin is cleaned with chlorhexidine solution and allowed to dry. A high-frequency linear ultrasound transducer (typically 10–15 MHz for superficial peripheral nerves) or curvilinear lower-frequency probe (5–8 MHz for deeper targets such as the lumbar plexus or coeliac plexus) is used to identify the nerve and surrounding anatomy in real time. The target nerve appears as a characteristic hyperechoic (bright) oval or round structure on ultrasound, often surrounded by the hyperechoic fibres of the nerve sheath. Neurovascular relationships — veins, arteries, fascial planes — are mapped before needle insertion. After skin infiltration with a small volume of subcutaneous local anaesthetic, a block needle (typically 50–100 mm, 22-gauge for peripheral blocks) is advanced under real-time ultrasound guidance in an in-plane or out-of-plane approach. Colour Doppler is used to confirm the needle tip is not within a blood vessel before injection. The syringe is aspirated before and during injection to exclude intravascular placement; injection proceeds in small increments (3 mL boluses) to detect any early signs of systemic toxicity (LAST — local anaesthetic systemic toxicity). The local anaesthetic is deposited around the nerve (perineural spread) rather than into the nerve (intraneural) — the characteristic hypoechoic ring around the nerve confirms correct placement. For continuous nerve block catheters, a Tuohy needle is used to thread a fine (20-gauge) catheter 3–5 cm beyond the needle tip alongside the nerve; the catheter is secured to the skin with a transparent dressing and connected to an elastomeric pump delivering 5–10 mL/hour of 0.1–0.2% ropivacaine. For therapeutic pain blocks, fluoroscopy (X-ray guidance) is used for epidural and facet joint injections to confirm needle position with contrast imaging before steroid injection.

Ultrasound-guided peripheral nerve blocks achieve successful anaesthesia or analgesia in over 90–95% of procedures in experienced hands — substantially higher than the 70–80% success rate of landmark-based or nerve stimulator techniques. The opioid-sparing effect of nerve blocks is one of their most clinically important benefits: effective regional anaesthesia reduces or eliminates the need for systemic opioids, thereby reducing opioid-associated adverse effects including nausea and vomiting (the leading cause of delayed discharge and patient dissatisfaction after surgery), sedation, respiratory depression, ileus, urinary retention, and chronic opioid dependence. The multicentre RECHARGE trial and numerous systematic reviews confirm that peripheral nerve block-based anaesthesia reduces post-operative nausea and vomiting rates by 30–50%, reduces opioid consumption by 50–70% in the first 24 hours, enables earlier hospital discharge in ambulatory procedures, reduces time to first mobilisation after joint replacement, and improves patient satisfaction scores. For chronic pain management, therapeutic nerve blocks with local anaesthetic and corticosteroid provide clinically meaningful pain relief (greater than 50% reduction in pain VAS score) in 60–80% of appropriately selected patients for lumbar facet joint pain, cervicogenic headache, and radiculopathy. Radiofrequency ablation of medial branch nerves following positive diagnostic facet joint blocks extends pain relief to 12–18 months in 60–70% of patients, representing a cost-effective chronic pain management strategy. Coeliac plexus neurolysis for pancreatic cancer pain achieves pain reduction in 80–90% of treated patients, significantly reducing opioid requirements and improving quality of life.

Nerve blocks are generally very safe procedures when performed by trained anaesthesiologists or pain physicians using ultrasound guidance and strict aseptic technique. Local anaesthetic systemic toxicity (LAST) — the most feared acute complication — occurs from inadvertent intravascular injection or rapid vascular absorption, leading to cardiovascular and central nervous system toxicity (CNS symptoms: ringing in ears, perioral tingling, metallic taste, seizures; cardiovascular: arrhythmia, cardiac arrest with bupivacaine). LAST occurs in approximately 0.01–0.1% of peripheral nerve blocks; real-time ultrasound guidance, incremental aspiration, fractional injection, and LAST awareness with readily available Intralipid 20% emulsion have substantially reduced its frequency and severity. Nerve injury causing persistent sensory or motor deficit occurs in under 0.1% of peripheral nerve blocks — ultrasound guidance enabling direct nerve visualisation has further reduced intraneural injection events compared with blind techniques. Haematoma at the injection site occurs in under 1% and is usually self-limiting. Pneumothorax is a recognised complication of interscalene brachial plexus and supraclavicular blocks (proximity to apex of lung) — incidence under 0.5% with ultrasound guidance versus 1–3% with landmark technique. Phrenic nerve palsy causing ipsilateral diaphragm paralysis occurs in virtually 100% of interscalene blocks (the C3, C4, C5 phrenic nerve roots are in the injection field) — this causes a 20–25% reduction in pulmonary function, generally well tolerated in healthy patients but potentially hazardous in those with pre-existing respiratory compromise. Block failure (incomplete or failed anaesthesia) requiring supplemental local infiltration or conversion to general anaesthesia occurs in approximately 3–8% of peripheral blocks and up to 10–15% in technically challenging cases. Infection at the catheter site for continuous nerve blocks is rare (under 0.5%) but is managed by catheter removal and antibiotics.

The onset of nerve block effect (numbness and weakness in the blocked territory) develops progressively over 15–30 minutes following injection of long-acting local anaesthetic (bupivacaine or ropivacaine). Patients are monitored in a recovery area until the block is confirmed effective before proceeding to surgery or discharge in the ambulatory pain procedure setting. The blocked limb or area is numb and may be weak — patients with lower limb blocks cannot weight-bear safely until motor function returns and must be assisted with mobility. Protective measures include padding bony prominences of the numb limb, avoiding extreme positions that could cause pressure injury, keeping the limb warm (as it will not feel cold or temperature), and not putting the numb arm in a hot bath or against a hot surface. Single-shot block duration is 8–20 hours for bupivacaine (concentration and volume dependent) and 12–24 hours for ropivacaine; patients should anticipate when numbness will wear off and have oral analgesics ready (paracetamol 1g four times daily and ibuprofen 400 mg three times daily) to begin 1–2 hours before expected block offset to minimise the rebound pain that some patients experience when the block wears off. Continuous nerve block catheters are managed at home with a take-home elastomeric pump providing 5 days of analgesia; patients and caregivers receive written instructions for managing the catheter, troubleshooting pump issues, and recognising signs of catheter infection (redness, swelling, purulent discharge at insertion site). Catheter removal is simple and can be performed by the patient at home by pulling the catheter out gently and applying a small dressing. Follow-up for chronic pain nerve blocks is arranged at 4–6 weeks to assess the response to treatment and plan the next step in the pain management programme.