Safety of pre-incisional low-dose ropivacaine infiltration in bilateral axillo-breast approach thyroidectomy: a retrospective study

Introduction
Ropivacaine is widely used as a local analgesic, but it has toxicity that is related to the concentration, and highly concentrated ropivacaine can induce motor nerve blockage. Aim: To investigate the safety of low-concentration pre-incisional ropivacaine injection for postoperative pain control and compare postoperative adverse events between a low-concentration ropivacaine injection group and a high-concentration ropivacaine injection group.

Material and methods
Patients who underwent thyroidectomy via the bilateral axillo-breast approach (BABA) between June 2017 and October 2021 performed by a single surgeon at Samsung Medical Center were retrospectively identified. These outcomes were compared between the two groups after 1 : 1 propensity score matching.

Results
From a total of 633 patients, 620 patients were selected. There were 527 in the low-concentration ropivacaine group and 93 in the high-concentration ropivacaine group. After propensity score matching, two comparable groups with 93 patients in each were obtained. The incidence of ropivacaine-related adverse events was similar between the two groups (p = 0.186) but the occurrence of postoperative bradycardia (p = 0.048) was lower in the low-concentration ropivacaine group than in the high-concentration ropivacaine group. Other outcomes such as postoperative pain scores (p = 0.363), postoperative nausea and vomiting (p > 0.999), and postoperative opioid consumption (p = 0.699) were similar between the two groups.

Conclusions
Pre-incisional low-concentration ropivacaine injection was effective for postoperative pain control and can be safely used in BABA thyroidectomy.