Question

During an interscalene block, you observe diaphragmatic twitching when stimulating a nerve. Which nerve is likely being stimulated, and where should you move the needle to prevent this stimulation?

a) Brachial plexus
b) Phrenic nerve
c) Radial nerve
d) Ulnar nerve

Answer 1

Diaphragmatic twitching during an interscalene block indicates stimulation of the phrenic nerve, and the needle should be moved to prevent this to avoid affecting the patient's breathing.

Step-by-step explanation:

When observing diaphragmatic twitching during an interscalene block, the nerve likely being stimulated is the phrenic nerve. The needle should be repositioned to prevent stimulation of this nerve and ensure that the brachial plexus is adequately blocked without affecting the diaphragm. Since the phrenic nerve is connected to the spinal cord at cervical levels 3 to 5 and is responsible for the muscle contractions that drive ventilation, it is crucial to avoid its stimulation during the procedure to prevent diaphragmatic movement, which can lead to breathing difficulties for the patient.