A vascular access needle assembly is provided. A terminal measures channel information in the time domain and transmits it to a base station. The liposomal compositions are characterized by high drug-to-lipid ratios and provide long term analgesia. However, the backing plate may comprise one or more layers of metal, ceramic or polymer-based composites. Measures of pulse amplitude are obtained from the signal, and pacing interval optimization is performed based on the measures of pulse amplitude. Hand switches are placed in the range of the natural swing of the surgeon’s thumb, whether gripping the surgical instrument right-handed or left handed.