Background and Aims Various diaphragm-sparing alternatives to interscalene block have been studied. Costoclavicular block(CCB) as the alternative, demonstrated low hemidiaphragm paralysis(HDP) occurrence but inconsistent analgesic effect in our previous study. We hypothesized that a larger volume for CCB could provide sufficient analgesia by achieving supraclavicular spreading. Therefore, we compared analgesic efficacy and HDP occurrence of two different volumes of local anesthetic(LA) for CCB in arthroscopic shoulder surgery.

Methods Sixty patients who scheduled for elective arthroscopic rotator cuff repair were randomly allocated into either of groups; CCB20(0.75% ropivacaine 20mL) or CCB40(0.375% ropivacaine 40mL). After induction and CCB, supraclavicular spreading at supraclavicular fossa and HDP were evaluated with ultrasound observation. The primary outcome was the rate of participants who reported zero pain score at rest 1 hour postoperatively. Postoperative analgesia outcomes and outcomes HDP related were evaluated.

Results The rate of complete analgesia with NRS 0 at PACU were 23.3%(7/30) in CCB20 and 33.3%(10/30) in CCB40(p=0.567). The pain score at 1 hour postoperatively was no significantly different between the groups(3 [1 to 5] in CCB20 vs 2 [0 to 4] in CCB40; p=0.395). There were no statistically significant differences between the groups(p<0.098) in complete HDP occurrence. Multivariate logistic regression analysis showed that the ultrasound observation of supraclavicular spreading was significantly associated with no and mild pain(pain score <4) at immediate postoperative period regardless allocated group.

Conclusions The larger volume of LA doesn’t guarantee supraclavicular spreading of CCB. Observing supraclavicular spreading using the ultrasound after CCB can be used as a tool to predict acute pain after shoulder surgery.