Modified longitudinal intermediate cervical plexus block for supraclavicular nerve analgesia: a randomized,...

The superficial cervical plexus block (SCPB) is routinely employed for clavicle surgery due to the dominant innervation of the surgical field by the supraclavicular nerves (SN). However, evidence directly comparing the blocking effect of different SCPB approaches-particularly the novel modified longitudinal intermediate cervical plexus block (MU)-on SN coverage and phrenic nerve safety remains limited. This randomized, double-blind, controlled trial in healthy volunteers aimed to evaluate the efficacy of MU relative to landmark-based and ultrasound-guided intermediate approaches in achieving SN blockade at 20 min, while assessing diaphragmatic paralysis as a key safety outcome. We hypothesized that MU would enhance SN blockade success.

In this randomized, double-blind, controlled volunteer trial, 45 healthy adults received one right-sided SCPB using one of three approaches: a landmark-based SCPB within the superficial cervical fascia (LM), an ultrasound-guided intermediate cervical plexus block at the C4 transverse process level (US), or the MU. All blocks used 10 mL of 0.5% ropivacaine. Blockade of superficial cervical plexus branches was assessed at 5, 10, 15, and 20 min. The primary outcome was supraclavicular nerve block (SNB) success within 20 min. Secondary outcomes included hemidiaphragmatic excursion and ordered grades of paralysis during quiet and deep breathing, oxygen saturation, and complications.

SNB success rates at 20 min were 0% (LM), 40.0% (US), and 73.33% (MU) (p < 0.001). During quiet breathing, complete diaphragmatic paralysis occurred in 0% (LM), 0% (US), and 33.33% (MU), with partial paralysis rates of 13.33%, 53.33%, and 26.67%, respectively (p = 0.005). Deep breathing results mirrored this trend. Oxygen saturation and complication rates showed no significant intergroup differences.

In this volunteer study, the MU approach resulted in a higher rate of SN sensory block at 20 min compared to LM and US techniques, but was associated with an increased incidence of diaphragmatic paralysis. These findings warrant further investigation in surgical populations.

ChiCTR2500104036 (Retrospective registration. Registration date: June 10, 2025).