The Effect of Interscalene Peripheral Nerve Block With 0.25% Bupivacaine vs 0.125% Bupivacaine on Lung Function

The Effect of Interscalene Peripheral Nerve Block With 0.25% Bupivacaine vs 0.125% Bupivacaine on Lung Function

Investigation Into the Effect of 0.25% Bupivacaine for Interscalene Peripheral Nerve Block vs 0.125% Bupivacaine on Pulmonary Function

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.

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.

Lung function was evaluated by examining diaphragm movement using ultrasound imaging and change in room air oxygen saturation (SpO2). Diaphragm movement was assessed using ultrasound as Normal (diaphragm moves caudad with inspiration), Abnormal (diaphragm does not move caudad with inspiration), and Paradoxical (diaphragm moves cephalad with inspiration). Both diaphragm function and room air SpO2 were assessed prior to any intervention to establish a baseline, and again on discharge from the PACU, within 5 hours of the completion of surgery.

Pain relief was assessed by recording the amount of opioid administered intraoperatively and in the PACU. The Visual Analogue Score of pain scores (0-10, with 0 being no pain and 10 being the worst pain imaginable) were recorded at the time of discharge from the PACU, within 5 hours of the completion of surgery.

A follow-up phone call was made to patients within 30 days of surgery to assess the presence of any complications related to the block and overall satisfaction with pain control. Overall satisfaction was assessed on a 7-point Likert scale of 1-not at all satisfied with pain control 2-mostly unsatisfied with pain control 3-slightly unsatisfied with pain control 4-no opinion 5-slightly satisfied with pain control 6-mostly satisfied with pain control 7-completely satisfied with pain control.

Inclusion Criteria: patients presenting for outpatient rotator cuff repair adults English as the primary language Exclusion Criteria: evidence of peripheral nerve damage on affected side refusal of peripheral nerve block pregnant women lung disease, including obstructive sleep apnea chronic opioid use mental handicap