We measured the spread of radiocontrast in the interscalene space after injection under low (<15 psi) and high (>20 psi) pressures.METHODS:
Nine healthy volunteers received ultrasound-guided injections of 10 mL radio-opaque NaCl 0.9% in both interscalene spaces. Spread of injectate as assessed by computed tomography scan and discomfort on injection were recorded.RESULTS:
Under both opening pressure conditions, injectate contacted 3 brachial plexus roots and spilled over the surface of the anterior and/or middle scalene muscles underneath the cervical fascia.CONCLUSIONS:
Regardless of injection pressure, the interscalene space was filled with 10 mL of radiocontrast injectate.