1. Field of the Invention
The present invention relates to a haemodialysis device including an extracorporeal circulatory system in which blood from a patient is passed via a blood supply line to the blood chamber of a haemodialyser, which is divided into two chambers by a semi-permeable membrane, and from the blood chamber to the patient via a blood return line. The device further comprises a blood pump to supply the blood though the extracorporeal blood circulatory system, an addition unit for adding a substance to the blood of the patient, an ultra-filtration unit for withdrawing fluid from the second chamber of the dialyser, a blood pressure measuring unit for measuring the blood pressure of the patient, and a control and evaluation unit which is connected to the blood pump, the addition unit, the ultrafiltration unit and the blood pressure measuring unit. The device further includes an output unit for outputting information which is connected to the control and evaluation unit, comprising an input for inputting data and instructions which is connected to the control and evaluation unit.
2. Description of Related Art
In haemodialysis blood is removed continuously form a patient in an extracorporeal circulatory system, passed through a haemodialyser and re-infused back to the patient.
In this case, a metabolism similar to that of the kidneys is carried out. The haemodialyser consists of two chambers separated by a semi-permeable membrane, of which blood flows through one and a purifying fluid—the dialysis fluid—flows through the other. For this purpose the commercially available haemodialysers have thousands of hollow fibres whose walls are semi-permeable. The blood is passed through the interior of the hollow fibres whilst the dialysis fluid is generally fed in the opposite direction in the fibre interior intermediate space and removed.
The dialysis fluid has concentrations of blood components such as electrolytes which approximately correspond to those of a healthy person so that the corresponding concentrations in the blood can be kept at a normal level.
Substances to be removed from the blood such as creatinine or urea are not contained in the dialysis fluid whereby these can be removed from the blood merely by diffusion as a result of the concentration gradient at the membrane.
Excess water is removed from the blood by convection or ultra-filtration with the aid of a pressure gradient.
Haemodialysis devices are used to control these processes and usually also prepare the dialysis fluid from water and concentrates with the correct concentration and temperature. At the same time, these devices are increasingly in a position to take over a wide range of monitoring actions of the haemodialysis treatment in order to keep any danger to the patient as low as possible and allow countermeasures to be taken in good time in the event of complications.
Among the complications, drops in blood pressure are of particular importance. Problems of this kind arise in 40-50% of treatments. In approximately 20-30% of treatments the dialysis must be interrupted by the user and the blood pressure status of the patient restored. In this case, the user must carry out an always similar sequence of actions on the dialysis machine which binds him to exclusive operation of the dialysis machine for about 1-2 minutes instead of being able to devote himself directly to the patient.
These measures comprise a reduction in the blood flow in order to prevent arterial alarms at the blood pressure sensors in the blood supply line of the extracorporeal circulatory system, stopping ultra-filtration in order to prevent a further withdrawal of volume, starting blood pressure measurements in order to obtain the current blood pressure status of the patient and administering a substance into the patient's blood in order to increase the blood volume status of the patient. This can be achieved by increasing the concentration of a substance such as sodium chloride in the dialysis fluid, where sodium chloride enters into the blood through the membrane merely as a result of the difference in concentration without any significant displacement of volume. However, this can also be achieved by a volume infusion in the form of a bolus directly into the lines of the extracorporeal blood circulatory system or through the membrane of the dialyser.
EP 0 311 709 A1 discloses a haemodialysis device in which the blood pressure and the heart rate of a patient are continuously monitored. If the measured values lie outside certain ranges of values, the machine independently initiates countermeasures to stabilise the patient's circulation without any action by the staff. These measures comprise reducing the ultrafiltration and raising the sodium concentration in the dialysis fluid. According to the teaching of EP 0 311 709 A1, the dialysis staff should only be involved after unsuccessful, automatically initiated countermeasures.
EP 0 911 044 A1 of the applicant also has as its subject matter an automated intervention in the treatment. The blood pressure can be continuously monitored especially well using pulse wave transmission time measurements. In this case, the user can specify which measures should be introduced by the haemodialysis device when a drop in blood pressure occurs. These measures comprise lowering the temperature of the dialysis fluid, switching off the ultra-filtration, application of a bolus of sodium chloride solution and changing the composition of the dialysis fluid.
In order to avoid hypotonic phases, WO 94/27658 A1 proposes a manually actuatable device at a haemodialysis device which when actuated delivers additional sodium into the dialysis fluid.
In the case of manual interventions which are of great importance in practice as previously, several steps must frequently be instigated one after the other, as already described, which takes a certain space of time. In this case, the haemodialysis device confirms the individual measures differently, under which a clear presentation of the information and user guidance suffers.