Liquid purification or separation – Processes – Including controlling process in response to a sensed condition
Reexamination Certificate
1999-03-04
2001-03-13
Kim, John (Department: 1723)
Liquid purification or separation
Processes
Including controlling process in response to a sensed condition
C210S085000, C210S090000, C210S096100, C210S097000, C210S134000, C210S138000, C210S143000, C210S195200, C210S257100, C210S258000, C210S321710, C210S416100, C210S433100, C210S645000, C210S646000, C210S650000, C210S739000, C210S805000, C210S929000, C604S004010, C604S005010
Reexamination Certificate
active
06200485
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a system and method of blood filtration, and more particularly a continuous system and method for the regulation of the rate of filtration of fluid and/or soluble waste from the blood of a patient based on one or more monitored patient parameters.
BACKGROUND OF THE INVENTION
For various reasons, including illness, injury or surgery, patients may require replacement or supplementation of their natural renal function in order to remove excess fluid or fluids containing dissolved waste products from their blood. Several procedures known for this purpose are dialysis, hemodialysis, hemofiltration, hemodiafiltration and ultrafiltration; another related procedure is plasmapheresis. The specific procedure employed depends upon the needs of the particular patient. For example, dialysis is used to remove soluble waste and solvent from blood; hemofiltration is used to remove plasma water from blood; hemodiafiltration is used to remove both unwanted solute (soluble waste) and plasma water from blood; ultrafiltration is a species of hemofiltration; and plasmapheresis is used to remove blood plasma by means of a plasmapheresis filter. Because the replacement of renal function may affect nutrition, erythropoiesis, calcium-phosphorus balance and solvent and solute clearance from the patient, it is imperative that there be accurate control of the procedure utilized. The accurate control of the rate of removal of intravascular fluid volume is also important to maintain proper fluid balance in the patient and prevent hypotension.
Various systems have been proposed to monitor and control renal replacement procedures. For example, U.S. Pat. No. 4,132,644 discloses a dialysis system in which the weight of dialyzing liquid in a closed liquid container is indicated by a scale. After the dialyzing liquid flows through the dialyzer, the spent liquid is returned to the same container and the weight is again indicated. Since the container receives the original dialyzing liquid plus ultrafiltrate, the amount of ultrafiltrate removed from the patient is equal to the increase in total weight in the container. This system is not driven by a weight measuring device and does not offer precise control of the amount of liquids used in the procedure.
U.S. Pat. No. 4,204,957 discloses an artificial kidney system which utilizes weight measurement to control the supply of substitute fluid to a patient. In this system, the patient's blood is pumped through a filter and the filtrate from the blood is discharged to a measuring vessel associated with a weighing device. A second measuring vessel containing substitute fluid is associated with a second weighing device and is connected to the purified blood line. By means of a pump, the substitute fluid and the purified blood are pumped back to the patient. The first and second weighing devices are coupled to one another by a measuring system in such a way that a fixed proportion of substitute is supplied to the purified blood stream from the second measuring vessel depending an the weight of the filtrate received in the first measuring vessel. This system does not utilize circulating dialysate fluid in the blood filtration.
U.S. Pat. No. 4,767,399 discloses a system for performing continuous arteriovenous hemofiltration (CAVH). The disclosed system relies upon utilizing a volumetric pump to withdraw a desired amount of fluid from the patient's blood and return a selected amount of fluid volume to the patient.
U.S. Pat. No. 4,923,598 discloses an apparatus for hemodialysis and hemofiltration which comprises an extracorporeal blood circuit including a dialyzer and/or filter arrangement. The system determines fluid withdrawal per unit time and total amount of fluid withdrawn by utilizing flow sensors in conjunction with an evaluating unit located upstream and downstream of the dialyzer or filter arrangement in the blood circuit.
U.S. Pat. No. 4,728,433 discloses a system for regulating ultrafiltration by differential weighing. The system includes a differential weighing receptacle having an inlet chamber and an outlet chamber which allows a fixed amount of fresh dialysate, by weight, to flow through the hemodialyzer. This system operates in a sequence of weighing cycles during which the amount of ultrafiltrate removed from the blood may be calculated. Additionally, the ultrafiltration rate for each weighing cycle may be calculated. This system provides a mechanism for determining and regulating the amount of ultrafiltrate removed from the blood while delivering dialysate to the patient in alternating fill and drain cycles of the inlet and outlet chambers of the differential weighing receptacle.
The need exists for a multipurpose renal function replacement/supplementation system which is accurate, reliable, capable of continuous, long-term operation, and which can be used effectively on adult, pediatric and neonatal patients.
SUMMARY OF THE INVENTION
The present invention is directed to a multipurpose system and method for removal of fluid and/or soluble waste from the blood of a patient: ultrafiltration only, hemodiafiltration, hemodiafiltration and ultrafiltration, and plasmapheresis with or without fluid replacement. The system and method of the present invention can provide reliable, long term operation (5-10 days) with a great degree of accuracy (on the order of+−2 grams regardless of the total volume of fluid passing through the system). The system and method of the invention are advantageous because of the multipurpose nature thereof, the repeatability and accuracy of the processes, and the simultaneous, continuous flow of fluids in an extracorporeal blood circuit, while being equally applicable to adult, pediatric and neonatal patients.
As used herein the term “hemofiltration” is to be broadly construed to include hemodialysis, hemofiltration, hemodiafiltration, ultrafiltration and plasmapheresis processes. As used herein, the term “infusate” is defined to include dialysate fluid or any other replacement fluids which may be supplied to the patient as a part of the hemofiltration procedures.
In a preferred embodiment, the system of the present invention includes a hemofilter, a blood pump for pumping blood from a patient through the hemofilter and back to the patient, and suitable tubing for carrying the pumped blood to and from the patent. The system further includes a first reservoir for maintaining a supply of infusate, a first weighing means for continuously monitoring the weight of the infusate and generating weight data signals correlated to the monitored weight, and a first pump for pumping the infusate from the first reservoir to the hemofilter or appropriate blood tubing access port. A second reservoir receives drained fluid (e.g., spent infusate or ultrafiltrate, including the fluids and solutes removed from the blood) from the hemofilter, and a second weighing means monitors the weight of the drained fluid and generates weight data signals correlated to the monitored weight. A second pump pumps the drained fluid from the hemofilter to the second reservoir. The system also includes a computerized controller operably connected to the blood pump, the infusate pump, the drain pump and the first and second weighing means.
The controller periodically, but on an ongoing basis during the treatment, interrogates at predetermined intervals the weight data signals that are continuously generated by the first and second weighing means and is designed to determine therefrom the weight of infusate and drained fluid in the first and second reservoirs at the predetermined intervals. The rate of fluid withdrawal from the blood is also determined. The controller compares the infusate and drained fluid weights to corresponding predetermined computed weights in the memory of the controller, and, when necessary, the controller generates control signals which automatically adjust the pumping rates of the infusate and drained fluid pumps in order to achieve a preselected amount of fluid removal from
Benzing, III George
Bissler John J.
Hemasilpin Nat
Kitaevich Yuli
Marchevsky J. Gabriel
Chidren's Hospital Medical Center
Kim John
Wood Herron & Evans L.L.P.
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