Deep Serratus Anterior Plane Block vs Surgically-placed Paravertebral Block for VATS Surgery

Post-thoracotomy pain syndrome is an unwanted complication of thoracic surgery. Poorly controlled pain may precipitate increased morbidity in the immediate and early postoperative periods due to its adverse effects on respiratory mechanics and mobilisation, which may result in further morbidity such as postoperative pulmonary complications and thrombosis. Poor perioperative management of this pain may also result in the development of chronic pain. Enhanced recovery, particularly functional recovery has become an important goal in the perioperative management of our patients. A key principle of this pathway is multimodal opioid-sparing analgesia to facilitate improved recovery and patient outcomes. Regional anaesthesia forms the cornerstone of this multimodal analgesia regimen.

Traditionally, thoracic epidural and thoracic paravertebral blockade have been the main forms of regional anaesthesia utilised in thoracic surgical patients undergoing lung resection. With the increasing use of minimally invasive thoracic surgery and with a cohort of patients who may not always be suitable for central neuraxial blockade, alternatives are needed. More recently, there has been an emerging use of interfascial plane blocks in this patient group. The interest in these techniques is derived from case reports, case series, cadaveric studies, and small clinical trials, which have demonstrated clinical efficacy in a variety of elective and emergency thoracic surgical procedures and also in chronic thoracic pain syndromes.

The deep serratus anterior plane (deep SAP) block is a relatively new interfascial plane regional anaesthesia technique, which has been postulated to provide analgesia of the entire hemithorax. The mechanism of its analgesic effects are believed to occur via blockade of the lateral cutaneous branches of the thoracic intercostal nerves (T2-T12), which produces analgesia of the anterolateral chest wall. A recent anatomical study by Mayes et al. demonstrated consistent blockade of the lateral cutaneous branches of the intercostal nerves. Clinical studies, although small, have shown dermatomal spread in the T2 - T9 distribution of the anterolateral chest wall. Therefore, this block presents a potential alternative to central neuraxial blockade.

However, whether SAP blockade can produce non-inferior analgesia compared with either thoracic epidural or thoracic paravertebral, both in terms of somatic +/- autonomic blockade, and the reliability of dermatomal spread, has been questioned by some.

The aim of this randomised controlled trial is to demonstrate non-inferiority of ultrasound-guided continuous deep serratus anterior plane blockade compared with surgically-placed continuous paravertebral blockade, for perioperative analgesia, in the patients undergoing minimally-invasive videoscopic thoracic surgery.

Inclusion criteria

• All adults greater than or equal to 18 years of age presenting for minimally-invasive thoracic surgery.

Exclusion criteria

• Patient refusal.
• Local infection at site of insertion.
• Allergy to amide local anaesthetics, opioids, paracetamol, NSAIDs, ketamine, NMBs, volatile anaesthetics.
• Concurrent use of antiarrhythmics with local anaesthetic activity.
• Concurrent use of MAOIs or within 2 weeks of MAOI use.
• Severe renal, liver or cardiac dysfunction.
• Coagulopathy/ anticoagulants that preclude use of PVB/ SAP techniques.
• Inability to comprehend pain scoring system.
• Elderly or frail patients that require a reduction in levobupivacaine dose commensurate with their physical status, resulting in the protocol not being followed.
• Pregnancy, breastfeeding.