A sensor assembly is provided that includes a skeletal frame comprising a loop structure. According to the present invention, a catheter is inserted through an incision into a large blood vessel of a patient. The high voltage op amp includes a high voltage input stage and a high voltage common source amplifier to expand the output voltage range to multiple times the normal operating voltage of the op amp. Thus, the system improves dynamic load response without compromising no-load power consumption. Also provided is an anti-fatigue agent containing at least one sesamin-class compound and at least one vitamin B1 class compound as the active ingredients.