BACKGROUND 

Continuous interscalene brachial plexus block (ISB) is widely used for arthroscopic shoulder surgery, but the incidence of hemidiaphragmatic paresis (HDP) has been reported to reach 100%. Several methods, including injections distal to the C5–C6 nerve roots, have been attempted to reduce the HDP incidence. However, catheter placement distal to the C5–C6 nerve roots interferes with the surgical site.

OBJECTIVE 

Our primary objective was to describe a new technique, the supraclavicular brachial plexus block (SCB), using the proximal longitudinal oblique approach (PLO-SCB), which can facilitate catheter placement and, when compared with ISB, to test whether this would provide noninferior analgesia and spare the phrenic nerve.

DESIGN 

Prospective, randomised, double-blind study.

SETTING 

Operating rooms, postanaesthesia care unit, and wards.

PATIENTS 

Seventy-six patients aged 20 to 80 years scheduled for arthroscopic shoulder surgery.

INTERVENTIONS 

Patients were randomly assigned to the continuous PLO-SCB (n = 40) or the continuous ISB (n = 40) groups. All patients received an initial low-volume single-injection (5 ml 0.75% ropivacaine) followed by a patient-controlled infusion of 0.15% ropivacaine.

MAIN OUTCOME MEASURES 

The primary outcomes were the incidence of HDP and pain scores. Secondary outcomes were respiratory function, postoperative analgesic consumption, sensory and motor function, and complications.

RESULTS 

The HDP incidence was significantly lower in the PLO-SCB group than in the ISB group at 30 min after block injection: 0% (0 of 38 patients) and 73.7% (28 of 38 patients), respectively (P < 0.001). Similarly, at 24 h after surgery, the incidences were 23.7% (9 of 38 patients) and 47.4% (18 of 38 patients) in the PLO-SCB and ISB groups, respectively (P = 0.002). Median [IQR] NRS pain scores at rest measured after surgery in the ISB and PLO-SCB groups were similar: immediately after surgery, 1 [0 to 2] vs. 1 [0 to 1], P = 0.06); at 30 min, 2 [0.25 to 2] vs. 1 [0 to 2], P = 0.065); and at 24 h 2 [0.25 to 3] vs. 1 [0 to 3], P = 0.47, respectively.

CONCLUSION 

For major shoulder surgery, compared with continuous ISB, continuous PLO-SCB was more sparing of diaphragmatic and respiratory function while providing noninferior analgesia. Catheter placement via the PLO approach is feasible without interfering with the surgical field.

TRIAL REGISTRATION 

Registered by the Clinical Trial Registry of Korea (Seoul, Korea; KCT0004759, http: cris.nih.go.kr, principal investigator: Hyungtae Kim).