Limitations and Technical Considerations of Ultrasound-Guided Peripheral Nerve Blocks: Edema and Subcutaneous Air

Objective: 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. Case Report: 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. Conclusions: 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.