In this multicentre randomised controlled trial, adult patients with isolated chest trauma and two or more unilateral rib fractures will be randomised to either serratus plane block and patient controlled analgesia or patient controlled analgesia alone. Our primary outcome is the static visual analogue scale score at one hour.

Rib breaks, or fractures, can cause pain that can be very difficult to manage and can result in chest infection and death. Such pain can be managed with either systemic drugs like morphine, which are given by mouth or through the veins, or local anaesthetic techniques, which can numb the painful area. Use of systemic drugs is however limited by significant side effects and traditional local anaesthetic techniques have problems of their own. Epidural analgesia, where local anaesthetic is placed near the spine, can only be done by those with a high level of technical skill and cannot be performed in patients with spine injuries, positioning difficulties and clotting problems. Complications and side effects can be common and/or serious and include failure, fall in blood pressure, and nerve and spinal cord damage. More recently, there has been interest in a new local anaesthetic technique, serratus plane block. Serratus plane block is simple to learn and can be done without any need for repositioning of the patient. It avoids some of the complications and side effects related to other local anaesthetic techniques and is more easily looked after by nursing staff on the ward. In view of this, we are aiming to recruit 44 adults with isolated chest injury and two or more rib fractures on one side. Each patient will either receive a serratus plane block in conjunction with morphine through the veins or just morphine alone. Our main aim is to assess how bad the pain is at 1 hour, but we will also compare the pain score, morphine consumption, lung function, level of sleepiness, and the frequency of low blood pressure, nausea and vomiting and slow breathing over the first 72 hours, as well as the hospital length of stay and occurrence of lung infection within 30 days.

Inclusion Criteria:

• 18 years of age or older
• Isolated chest trauma
• Two or more unilateral rib fractures

Exclusion Criteria:

• One unilateral rib fracture
• Bilateral rib fractures
• Flail chest
• Clavicular fractures
• Polytrauma
• Sternal fracture or injury
• Thoracic spine injury
• GCS less than 15
• Acute or chronic confusional state
• Delirium or psychiatric illness
• Chronic lung disease necessitating home nebulisers and/or oxygen
• Coagulopathy, defined as a platelet count less than 100 x 109/l , PT >15 or APTT >38
• End stage liver disease
• Severe congestive cardiac failure
• Significant renal failure, defined as a creatinine >150µmol/l
• Local infection at potential site of SBP insertion
• Pregnancy or breastfeeding
• History of chronic pain or opioid dependence
• Current chronic analgesic therapy, not to include paracetamol, NSAIDs and/or codeine
• Requirement for tracheal intubation and mechanical ventilation
• Allergy to local anaesthetics and/or opioids
• Inability to control and self-administer opioids with PCA due to confusion, learning difficulties or poor manual dexterity
• Unable to speak and/or understand English
• Patients known to clinicians to be COVID-19 positive as determined by PCR or for whom there is a clinical suspicion that they might be COVID-19 positive will be excluded from the trial.