Abstract: A monitoring arrangement is provided for detecting for extreme pressure conditions in blood tubing lines of a hemodialysis system. The arrangement includes a first pushbutton switch and a pivoted lever arm. A clamping means is located at a first end of the lever arm for clamping the blood tubing line against the first pushbutton switch, and the other end of the lever arm opposes a second pushbutton switch. Under low pressure conditions, the blood pressure in the tubing is no longer sufficient to hold the first pushbutton switch closed. The switch then opens to signal a low pressure condition. Under high pressure conditions, the blood tubing pressure causes the lever arm to pivot so that the far end of the lever activates the second pushbutton switch, which signals a high pressure condition.