be in no danger for a short period while attempts are made to put the dialyzer apparatus back on stream in addition the citrate pump should be shut down after a period of time following shut down of the blood pump e g 4 minutes after monitoring of a bypass condition in the dialyzer 18 if the bypass problem is solved within the first delay period mentioned the calcium ion pump 42 can simply be resumed if the bypass problem is solved after the first delay and consequent shut down of the blood pump but prior to shut down of the citrate pump it is only necessary to resume the blood pump and calcium ion pump simultaneously if the bypass operation can only be rectified after a relatively long period all of the pumps should be resumed simultaneously those skilled in the art will readily appreciate that the foregoing control sequences can be easily established using conventional sensors and control circuitry to carry out a hemodialysis using the apparatus illustrated in the figure blood is withdrawn from the patient and the inflow of citrate is simultaneously initiated blood flow rate is increased over the first 5 10 minutes of the procedure to 250 milliliters per minute maximum with or without charcoal perfusion calcium chloride replacement is begun after flow through the system is commenced both the citrate and calcium pumps once calibrated deliver reproduceable volumes that are insensitive to positive or negative pressures whole blood clotting time of the patient tends to decrease with time while that of the citrated blood remains beyond 30 minutes in the event.