Conditions: Diaphragm Paralysis
Keywords: bupivacaine concentration interscalene nerve block diaphragm function diaphragm weakness
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 30
Healthy volunteers: yes

Brief summary:
Peripheral nerve blocks are used to provide post-operative pain relief. Nerve blocks in the neck, in the interscalene area, provide pain relief after shoulder surgery but can cause temporary weakness or paralysis of the diaphragm. The investigators hypothesized that a lower concentration of bupivacaine would cause less weakness of the diaphragm but still provide good pain relief. Lung function and pain control was studied after interscalene peripheral nerve block with 20 milliliters of 0.25% bupivacaine or 0.125% bupivacaine.

Detailed description:
Prior to placement of interscalene brachial plexus peripheral nerve block (ISPNB), diaphragm function was assessed using ultrasound as normal, no movement, or paradoxical. Room air pulse oximetry (SpO2) was recorded. Patients were randomized to receive either 0.25% bupivacaine or 0.125% bupivacaine. ISPNB was performed using a coded syringe of the study drug, so that the anesthesiologists performing the nerve block, the patient, and the nurses assessing the patient were blinded as to the concentration. Patients were given a general endotracheal anesthesia for rotator cuff repair, and opioids were administered at the discretion of the attending anesthesiologist. When patients met criteria for PACU discharge, diaphragm function was again assessed using ultrasound and room air SpO2 was recorded.

Arms:
arm 1: interscalene nerve block with 0.25% bupivacaine arm 2: interscalene nerve block with 0.125% bupivacaine

Interventions: intervention 1: interscalene nerve block with 0.25% bupivacaine intervention 2: interscalene block with 0.125% bupivacaine
Intervention descriptions: intervention 1: interscalene nerve block performed with 20 ml of 0.25% bupivacaine intervention 2: interscalene block with 20 ml of 0.125% bupivacaine

Protocol document: