One of the most frequently performed peripheral nerve blocks (the injection of local anesthetic near nerves to block sensation/ movement to a specific part of the body) is the interscalene brachial plexus block for upper extremity surgeries. This type of block can unmask underlying respiratory issues such as shortness of breath due to a well-known and typically insignificant side effect of temporary diaphragmatic paralysis. The nerve block may be able to use saline solution to wash out the local anesthetic and potentially reverse this respiratory side effect. Specifically, the goal of this study is to determine if the injection of saline through the nerve block catheter reverses blockade of the phrenic nerve supplying the diaphragm, without affecting the ability of the nerve block to provide pain control after surgery.
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Change in forced vital capacity (FVC)
Timeframe: Before the nerve block placement, within 1 hour after the surgery, then in 5, 15, and 30 minutes after the saline injection/placebo (1 minute each for a total of 5 assessments)
Change in peak expiratory flow (PEF)
Timeframe: Before the nerve block placement, within 1 hour after the surgery, then in 5, 15, and 30 minutes after the saline injection/placebo (1 minute each for a total of 5 assessments)
Change in forced expiratory volume in 1 second (FEV1)
Timeframe: Before the nerve block placement, within 1 hour after the surgery, then in 5, 15, and 30 minutes after the saline injection/placebo (1 minute each for a total of 5 assessments)