Continuous Analgesia Using a Multi-Holed Catheter in Serratus Plane for Thoracic Surgery.

We read with great interest Mandabushi and colleagues commentary about Serratus Anterior Plane Block as a New Analgesic Technique for Post-Thoracotomy Pain (1). They concluded that SAP block is very easy to perform and provides excellent analgesia in patients undergoing thoracotomy with minimal side effects. We would like to describe its possible use and limitations for analgesic control for thoracic surgery. We have performed a serratus anterior plane (SAP) block using a multi-holed catheter (MHC) for continuous local anesthetic (LA) infusion in 6 patients undergoing videoassisted thoracoscopic surgery (VATS) for lobectomy and our experience, although very limited, allows us to draw interesting conclusions. Patients undergoing major open postero-lateral thoracotomy can suffer severe pain, which is sometimes hard to control with conventional analgesia that may develop into respiratory complications (2). Despite changes in the surgical technique of VATS with the use of small incisions (minithoracotomy about 5 cm and an accessory 1 cm incision), the possibility of rib damage, intercostal nerves injury, pulmonary parenchyma or pleura incision and pleura irritation (caused by haemostatic and sealer surgical glue applied to cover parenchyma defects and pleural drainage tube contact during postoperative period) can still be a problem. Despite several approaches for the pain management for thoracic surgery, the SAP block has as main purpose to cover chest skin incision pain by a sensory blockade allowing multiple perforating intercostal cutaneous branches of the intercostal nerves by LA injection contained between intercostals and serratus muscles interfascial plane (3). Whereas visceral pleura lacks of innervation, parietal sensory innervation is delivered from intercostal (subcostal branches) and phrenic nerves, in theory not attached by SAP block. Even though SAP block is performed in a superficial plane, given the proximity (0.5 – 1 cm) where LA is deposited on the pleura, diffusion across intercostal musculature may play an important role reaching extrapleural level and providing parietal pleura analgesia. This can be explained because of the better LA dispersion with MHC with a continuous infusion in the SAP and the evidence that muscles and fascias are porous tissues. To verify the existence of this effect, we conducted a series of cases with methylene blue instillation during SAP block performance for VATS to image the tissue coloration from an intrathoracic vision. We concluded that a potential spread exists through intercostals musculature to extrapleural space so LA reaching might be volume dependent. Another questionable matter would be the amount of LA used for a successful SAP block (4). Local anesthetic systemic toxicity may be a concern because of large doses of drug managed and due to the proxContinuous Analgesia Using a Multi-Holed Catheter in Serratus Plane for Thoracic Surgery