Intraoperative changes in upper extremity perfusion index after thoracic paravertebral and intertransverse process block in patients undergoing lung resection surgery.

Background: Perfusion index (PI) has been used as a surrogate marker of sympathetic blockade. This study evaluated changes in PI of bilateral upper extremity after thoracic paravertebral block (PVB) and intertransverse process block (ITPB).

Methods: This pilot study included three groups of patients undergoing elective unilateral pulmonary resection under general anesthesia with PVB (n=11) or ITPB (n=10), or urologic procedures with general anesthesia (control group, n=10). Blockades were performed using 10 mL aliquots of 0.5% ropivacaine administered at T3-4, T5-6, and T7-8 intercostal levels immediately after general anesthesia induction. The PI value of the operating side (PI-O) was divided by the contralateral side (PI-CL), and the relative change to baseline was assessed (relative PI-O/PI-CL), with a 50% increase considered meaningful.

Results: In all cases within the PVB and ITPB groups, a significant increase in PI was observed following the blockades. The median (1Q, 3Q) intraoperative relative PI-O/PI-CL values were 0.9 (0.8, 1.4), 2.1 (1.4, 2.5), and 1.4 (0.9, 1.9) in the control, PVB, and ITPB groups (P=0.01), respectively. Pairwise comparison revealed a significant difference only between the control and PVB groups (adjusted P=0.01). While the relative PI-O/PI-CL value in the control group generally remained close to 1, occasional fluctuations exceeding 1.5 were noted.

Conclusions: PVB induced a noticeable unilateral increase in upper extremity PI, whereas ITPB tended to result in an inconsistent and lesser degree of increase. Monitoring PI values can serve as an indicator of upper extremity sympathetic blockade, but consideration of potential confounders impacting these observations during surgery is essential. Further research is needed to validate these findings.