SNAP4 (Regional Anaesthesia Outcomes after Peripheral Nerve Blockade)

SNAP4 is funded by the British Journal of Anaesthesia/Royal College of Anaesthetists via the National Institute of Academic Anaesthesia and is sponsored by Guy's and St Thomas' NHS Foundation Trust.

Project Outline

SNAP4 is the fourth Sprint National Anaesthesia Project, delivered with the support of the RCoA Centre for Research and Improvement (CR&I), the Research and Audit Federation of Trainees (RAFT) and sponsored by Guy’s and St Thomas’ NHS Foundation Trust.

An estimated 500,000 peripheral nerve blocks are performed in the UK per year. They provide excellent pain relief and can avoid the need for general anaesthesia, but a small proportion of people experience neurological symptoms afterwards, such as numbness, tingling, weakness or unexplained pain. SNAP4 will follow up people after they have had a nerve block, to establish how often these symptoms occur, how long symptoms take to resolve and how recovery is affected.

The study will recruit adults receiving a peripheral nerve block as part of their routine surgical care over a 2-week snapshot period across approximately 100 UK hospitals. Recruitment is planned to begin in October 2027, with a pilot phase beforehand. Participants will be followed up by automated text message (SMS) at 24 hours, 48 hours, 3 months and 6 months, with more frequent follow-up for those reporting ongoing neurological symptoms. SNAP4 will collect high-volume, granular data on regional anaesthesia and will complement NAP8, the 8th National Audit Project, which is examining major complications of regional anaesthesia.

Background and Rationale

Regional anaesthesia is now a core part of anaesthetic practice and training in the UK, and its use continues to grow. It is also the most common source of anaesthesia-related litigation, with claims relating to peripheral nerve blocks doubling between 2008 and 2018. Despite this, there is no systematic reporting of outcomes after regional anaesthesia in the UK, and routine follow-up after nerve blocks is uncommon.

Postoperative neurological symptoms (PONS) after a nerve block usually resolve, but while they persist, they can affect recovery from surgery, cause pain and dysfunction, and generate considerable anxiety about whether the symptoms will be permanent. Patients contributing to a recent focus group described exactly this uncertainty.

Most of the existing evidence on PONS comes from retrospective work or from studies that predate modern practice, including routine ultrasound guidance, purpose-designed block needles, fascial plane blocks and lower doses of local anaesthetic. There is, therefore, a gap in contemporary, prospective data that clinicians can use when counselling patients about the recovery and risks of a nerve block and what to expect if symptoms occur.

A recent UK research priority-setting exercise led by RA-UK, involving patients, carers and healthcare professionals, placed patient safety at the heart of the specialty's research agenda. The design of SNAP4 will help to inform nine of the ten priority areas identified in that exercise. By describing the incidence, risk factors and trajectory of PONS and other outcomes, SNAP4 aims to improve shared decision making during consent, support better management of patients who develop symptoms, and guide improvements in clinical practice.

Study Design

SNAP4 is a national, multicentre, prospective observational cohort study. It is an observational study, so taking part does not change the care patients receive, but patients receive more detailed follow-up and reporting of outcomes. All clinical decisions, including the choice and conduct of the nerve block, remain with the usual care team.

Adults (aged 16 and over) receiving any peripheral nerve or fascial plane block for elective or emergency surgery will be invited to take part during a 2-week recruitment window. Following written informed consent, baseline information will be collected on the day of surgery, including patient characteristics and details of the anaesthetic, the nerve block and the operation.

Follow-up is then largely automated for most people. Participants will receive text message prompts linking to short online questionnaires at 24 hours, 48 hours, 3 months and 6 months after their block. Anyone reporting neurological symptoms attributable to the block at 48 hours enters more intensive follow-up, with daily messages for 2 weeks and then 4-weekly messages until symptoms resolve or 6 months have passed, whichever comes first. Each questionnaire takes around 5 to 15 minutes to complete. Data are collected and managed using NewcastlePROMS, a secure online platform used successfully in previous national studies.

Participants who report persistent neurological symptoms will be managed by their local hospital team in line with local pathways or national RA-UK and British Orthopaedic Association guidance, ensuring that anyone with ongoing symptoms receives appropriate clinical care alongside the study.

Research Objectives

The primary objective is to determine the incidence of PONS following peripheral nerve blockade and the time course to symptom resolution in adults having elective or emergency surgery.

Secondary objectives include to:

• Describe patient, anaesthetic and surgical characteristics in this population and examine whether any are associated with postoperative neurological symptoms
• Characterise the trajectory of sensory and motor recovery after nerve blockade, including the incidence of permanent nerve injury, defined as persistent neurological symptoms at 6 months
• Examine the incidence and severity of pain-related outcomes, including rebound pain, chronic post-surgical pain and persistent postoperative opioid use
• Report patient-reported outcomes including quality of recovery
• Describe the incidence and severity of short and intermediate-term complications of nerve blocks, including block failure, local anaesthetic toxicity, phrenic nerve palsy and pneumothorax

Get Involved

SNAP4 will recruit across approximately 100 hospitals in all four UK nations, and its success will depend on local collaborators at every participating site. As with previous SNAP projects, recruitment and data collection will be delivered by local teams, including anaesthetists in training working through the RAFT network, research nurses and other members of the perioperative team. Site registration details and collaborator information will be published here in due course.

Study Documents

The study protocol, ethics documents and site resources will be made available on this page once regulatory approvals are in place.

Meet the SNAP4 team