Introduction
The serratus anterior plane block (SAPB) is a regional anesthesia method whereby local anesthetics (LAs) are injected into the serratus anterior space to block the lateral cutaneous branch of the intercostal nerve, long thoracic nerve, and dorsal thoracic nerve[1]. It has been increasingly acknowledged that SAPB can produce effective analgesia for the chest wall because it fully covers surgical incisions impacted by thoracoscopic surgery and the site of the chest tube, which are often located in the anterolateral chest wall[2]. Continuous techniques are highly recommended for prolonged analgesia duration [3, 4], and we and others have successfully implemented continuous SAPB for multiple surgical procedures [2, 4-7], including video-assisted thoracoscopic surgery (VATS).
The efficiency of regional analgesia is importantly dependent on the volume and concentration of the LA solution[8]. However, potentially toxic plasma concentrations of LAs have been reported after administration of transversus abdominus plane (TAP) block[9, 10], especially in patients with hepatic or renal insufficiency. It has been commonly seen that SAPB is performed clinically using different concentrations of ropivacaine, ranging from a minimum of 0.125% ropivacaine to a maximum of 0.75% ropivacaine[11-13]. At present, the safety of different concentrations of ropivacaine in SAPB has not been well studied, especially under the condition of continuous administration of LAs. The objective of this prospective randomized study was therefore to compare the analgesic efficacy and pharmacokinetics of ultrasound-guided continuous SAPB using 0.2% and 0.375% ropivacaine in patients undergoing VATS.