Protective effects of C5 level saline injection around the phrenic nerve in interscalene brachial plexus block: a randomized controlled trial.

Interscalene brachial plexus block (ISB) frequently causes phrenic nerve palsy. This study investigated whether ultrasound-guided saline injection around the C5 phrenic nerve could lessen diaphragmatic paralysis during shoulder surgery. A randomized controlled trialrandomized 120 patients into either a saline or control group. The saline group received 10 mL of normal saline around the C5 phrenic nerve before the routine ISB; the control group received the standard ISB alone. The primary endpoint was the incidence of diaphragmatic paralysis, while secondary endpoints included analgesic effectiveness, respiratory complications, and patient satisfaction. Compared with the conventional ISB group, the saline group showed a markedly lower rate of complete diaphragmatic paralysis (13. % vs. 83. %, P < 0.001) and partial paralysis (13. % vs. 75. %, P < 0.001) after injection. Additionally, the saline group experienced faster onset of sensory and motor blockade (P < 0.001) and a longer block duration. Post-operative VAS scores were lower, respiratory complications were fewer, and patient satisfaction were higher in the saline group (all P < 0.001). Thus, saline injection around the C5 phrenic nerve reduces ISB-induced diaphragmatic paralysis, improves anaesthetic performance, and diminishes postoperative respiratory complications, thereby underscoring its clinical value.Clinical trial number: The study was registered with chictr.org.cn (ChiCTR2400094577) by Jing Zhao on December 25, 2024.