161 Incidence of pneumothorax from chest wall blocks for ambulatory breast cancer surgery in a high-volume practice

Background and Aims There is growing interest in regional anesthesia for breast surgery however many clinicians avoid paravertebral blocks (PVB) for fear of causing pneumothorax due to proximity to the pleura. Fascial plane blocks have been proposed as alternative approaches that may be safer for patients. We describe the rate of pneumothorax from PVB and serratus blocks in our high-volume practice. Methods This IRB-approved retrospective study assessed 2,793 patients who received a regional block for mastectomy from January 5, 2016 – April 22, 2020 subdivided by laterality and block type (Table 1). We calculated risk of pneumothorax (including 95% C.I.) for patients who received: at least one PVB; at least one serratus block; unilateral blocks; and bilateral blocks. All blocks were placed preoperatively with ultrasound-guidance by an experienced anesthesiologist or supervised trainee. Results PVB: 2251 patients, one pneumothorax. Complication rate 0.04%; 95% C.I. Serratus: 520 patients, one pneumothorax. Complication rate 0.2%; 95% C.I. Unilateral: 1081 patients, no pneumothorax. Complication rate 0%; 95% C.I. 0%, 0.3% Bilateral: 1712 patients, two pneumothoraces. Complication rate 0.1%; 95% C.I. Conclusions Pneumothorax is a rare complication of ultrasound-guided PVB and serratus blocks in a high-volume practice. This aligns with the prior findings of Pace1 in a retrospective study of 856 patients who received ultrasound-guided PVB, none of whom had suspected pneumothorax. We report a slightly higher rate of pneumothorax with serratus blocks, suggesting that fascial plane blocks are not necessarily ‘safer.’