Comparison between erector spine block (ESPB) to thoracic paravertebral plane block (TVPB) using ropivacaine plasma concentration analysis: a randomized double-blind clinical trial

Ultrasound-guided anesthesia popularized erector spinae plane block (ESPB) as an alternative to thoracic paravertebral block (TPVB) in video-assisted thoracic surgery (VATS). Concerns about systemic toxicity persist due to the large doses of local anesthetic used. This study compares arterial plasma concentration curves of ropivacaine between ESPB and TPVB to assess safety and toxicity.

This clinical trial was prospective, randomized, double-blind, controlled and with two parallel arms: 18 patients who received ESPB and 16 received TPVB (figure 1). Epidemiologic data were collected (table 1). All blockades were performed with the aid of ultrasound and after induction of general anesthesia. Ropivacaine plasma concentration were quantified every 2.5 minutes until 30 minutes. Continuous ropivacaine infusion via catheter began post-surgery and lasted 24 hours, with a subsequent blood sample collected.

Both groups showed similar modest plasma concentrations, with mean peak levels of 1.62 μg/ml (ESPB) and 1.70 μg/ml (TPVB). After continuous infusion, all concentrations dropped below 2 μg/ml (figure 2). No adverse intra or post-operative events were noted, and total plasma concentrations of unbound and free fraction of ropivacaine at 30 minutes did not significantly differ between groups.

Both blocks exhibited comparable plasma concentration curves, possibly due to factors beyond anatomical location, such as the pharmacokinetic properties of the local anesthetic or individual patient variability. In addition, similar unbound and free fraction plasma concentrations indicate uniformity in terms of proteinemia across the population. These results suggest that ESPB and TPVB are safe alternatives with comparable pharmacokinetics, guiding future dosage selection and more clinical studies.