The invention provides a system for continuously monitoring a patient during hemodialysis. The system includes a hemodialysis machine for performing the hemodialysis process that features a controller, a pump, a dialyzer filter, a lumen, and an interface to a body-worn monitor. A patient attaches to the dialysis machine through the lumen, and wears a body-worn monitor for continuously measuring blood pressure. The monitor includes an optical system for measuring an optical waveform, an electrical system for measuring an electrical waveform, and a processing component for determining a transit time between the optical and electrical waveforms and then calculating a blood pressure value from the transit time. The body-worn monitor features an interface (e.g. a wired serial interface, or a wireless interface) to transmit the blood pressure value to the controller within the hemodialysis machine. The controller is configured to receive the blood pressure value, analyze it, and in response adjust the dialysis process.
