Limitations and technical considerations of ultrasound-guided peripheral nerve blocks: edema and subcutaneous air

Despite advantages of ultrasound-guided peripheral nerve blocks as compared with established techniques, various limitations may exist. We present 2 trauma patients in whom the usefulness of ultrasound techniques was limited by edema and subcutaneous air.

Two male patients were admitted to the Intensive Care Unit due to multiple trauma. In the first patient, tissue edema and obesity (body mass index, calculated as weight [kg]/height [m(2)] = 35), and in the second patient, subcutaneous emphysema, were significant limitations for the application of ultrasound-guided peripheral nerve blocks. These factors made 2-dimensional ultrasound imaging difficult despite the use of tissue harmonic technique and advanced ultrasound equipment. Neurostimulation technique alone, or combined with ultrasound imaging eventually led to successful nerve block.

Ultrasound technique limitations do exist. We present 2 conditions, edema and subcutaneous air, which contributed to ultrasound failure to provide a clear image of the targeted nerves.