Hemodialysis system having clamping mechanism for peristaltic pumping

1. A hemodialysis system comprising:

a dialysis instrument;

first and second peristaltic dialysate pumps operated by the instrument;

a cassette including a rigid structure and first and second dialysate pumping tubes carried by the rigid structure; and

a mechanism configured to (i) initially allow the cassette to be accepted by the dialysis instrument and (ii) thereafter move a member downwardly onto the first and second dialysate pumping tubes for operation with the first and second peristaltic dialysate pumps.

2. The hemodialysis system of claim 1 , wherein the member includes a cam race that engages the first and second dialysate pumping tubes.

3. The hemodialysis system of claim 1 , wherein the mechanism includes at least one cam configured to rotate to move the member downwardly.

4. The hemodialysis system of claim 3 , wherein the mechanism includes at least one idler gear configured to rotate the at least one cam.

5. The hemodialysis system of claim 4 , wherein the mechanism is configured to move the member away from the first and second peristaltic dialysate pumps after the door is latched closed.

6. The hemodialysis system of claim 1 , wherein the mechanism is configured to move the member away from the first and second peristaltic dialysate pumps when a door for accepting the cassette is opened.

7. The hemodialysis system of claim 6 , wherein the mechanism is configured to move the member upwardly away from the first and second peristaltic dialysate pumps when a door for accepting the cassette is opened.

8. The hemodialysis system of claim 1 , which includes a motor, and wherein the mechanism is driven by the motor.

9. The hemodialysis system of claim 1 , wherein the mechanism is configured to engage the first and second dialysate pumping tubes at substantially the same time.

10. The hemodialysis system of claim 9 , wherein the mechanism is cam-operated to engage the first and second dialysate pumping tubes at substantially the same time.

11. The hemodialysis system of claim 1 , wherein the mechanism is configured to convert rotational motion to translational motion to engage the first and second dialysate pumping tubes.

12. The hemodialysis system of claim 11 , wherein the mechanism is configured to translate the member to engage the first and second dialysate pumping tubes, the member including slots formed by walls that ride along cams rotated by the mechanism.

13. A hemodialysis system comprising:

a dialysis instrument;

first and second peristaltic dialysate pumps operated by the instrument;

a cassette including a rigid structure and first and second dialysate pumping tubes carried by the rigid structure; and

a mechanism configured to initially allow the cassette to be loaded onto a moveable platform of the dialysis instrument, after which the moveable platform and the mechanism are moved so that the mechanism engages the first and second dialysate pumping tubes for operation with the first and second peristaltic dialysate pumps.

14. The hemodialysis system of claim 13 , wherein the platform is a door connected moveably to the instrument.

15. The hemodialysis system of claim 13 , wherein the mechanism is configured to move a member and the first and second dialysate pumping tubes towards each other to produce the operable engagement.

16. The hemodialysis system of claim 13 , wherein the instrument provides a blood circuit, a dialysate circuit operated by the first and second peristaltic dialysate pumps, and a dialyzer placed in communication with the blood circuit and the dialysate circuit, the system further configured to operate a priming sequence in which (i) dialysate is used to prime a first portion of the dialysate circuit and (ii) a physiologically compatible solution, other than dialysate, is used to prime a second portion of the dialysate circuit, the dialyzer and the blood circuit.

17. The hemodialysis machine of claim 16 , the first portion of the dialysate circuit including a recirculation loop primed by at least one of the first and second peristaltic dialysate pumps.

18. The hemodialysis machine of claim 17 , the second portion of the dialysate circuit located at least substantially between the recirculation loop and the dialyzer.

19. The hemodialysis machine of claim 18 , the second portion of the dialysate circuit primed by at least one of a blood pump and a downstream one of the peristaltic dialysate pumps.

20. A hemodialysis system comprising:

a dialysis instrument;

first and second peristaltic dialysate pumps operated by the instrument;

a cassette including a rigid structure and first and second dialysate pumping tubes carried by the rigid structure; and

a mechanism configured to (i) initially allow the cassette to be accepted by the dialysis instrument, (ii) thereafter move a member into engagement with the first and second dialysate pumping tubes for operation with the first and second peristaltic dialysate pumps, and (iii) when a door for accepting the cassette is opened, move the member away from the first and second peristaltic dialysate pumps.