Surgery – Blood drawn and replaced or treated and returned to body – Constituent removed from blood and remainder returned to body
Reexamination Certificate
1998-02-19
2003-06-24
Sykes, Angela D. (Department: 3762)
Surgery
Blood drawn and replaced or treated and returned to body
Constituent removed from blood and remainder returned to body
C210S646000, C210S650000, C210S652000, C210S900000, C422S044000, C604S006090
Reexamination Certificate
active
06582385
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to man-made apparatus that substitutes for natural kidney function, and more particularly to a compact, easy-to-use hemofiltration system in which ultrafiltrate is purified via reverse osmosis to create pure water, and infusate concentrate is combined with the purified ultrafiltrate to create infusate.
BACKGROUND OF THE INVENTION
Loss of human renal function, for example due to kidney disease, affects hundreds of thousands of people worldwide. In the past, chronic renal failure has meant almost certain death. More recently, renal failure is treatable by kidney transplant and/or less-physiologically traumatic procedures such as hemodialysis, hemofiltration or peritoneal dialysis (dialysis therapy). Existing hemodialysis and hemofiltration systems operate by withdrawing blood from a patient, treating the blood to remove waste, and re-introducing treated blood into the patient. Hemodialysis operates by bringing blood into contact with one side of a semipermeable membrane while a dialysis solution (dialysate) is brought into contact with the other side of the membrane. Uremic toxins diffuse out of the blood, through the semipermeable membrane due to a concentration gradient across the membrane, and into the dialysate. Hemofiltration operates by passing the blood through a filter to remove elements smaller than the filter pore size and replacing with a physiologic solution free of toxins (infusate).
The prior art contains examples of blood treatment devices that make use of combinations of multiple dialyzers, multiple filters, or combinations of filter and dialyzer. Kraus, et al., in “Urea-Rejecting Membranes and Their Application in the Development of a Miniature Artificial Kidney”,
J Memb. Sci.,
1, 115-127, 1976 describe a system for continuous regeneration of peritoneal dialysate water. A dialysis unit is provided for purifying peritoneal dialysis solution, and a filter continuously purifying dialysate provided to the dialysis unit.
Ghezzi, et al. (U.S. Pat. No. 5,194,157) describe a blood purification system including, in series, a hemofiltration element followed by a hemodialysis element. Blood from a patient is first filtered in the hemofiltration element, then passed through the hemodialysis element and returned to the bloodstream. Ultrafiltrate from the hemofiltration element can be regenerated by being passed through a second filter and introduced into the flow of blood between the hemofiltration element and the hemodialysis element.
Gigou, et al. (U.S. Pat. No. 3,926,797) describe a separation system that can be used for blood purification. The system includes an ultrafiltration cell that receives blood from a patient, filters the blood, and returns the filtered blood to the patient. The ultrafiltrate can be purified using a dialysis unit, the purified ultrafiltrate combined with filtered blood for re-introduction into the patient. A device such as an active charcoal column or an ion exchange resin column can be used to remove waste from the dialysate of the dialyzer.
Brown (U.S. Pat. No. 3,579,441) described a blood purification unit including an ultrafilter for filtering blood from a patient and returning filtered blood to the patient. The ultrafiltrate can be passed through a hyperfilter, the hyperfiltrate being combined with purified blood for re-introduction into the patient. A reservoir is provided for introduction of make-up electrolyte into the hyperfiltrate for re-combination with the filtered blood. While the above-noted and other systems represent, in many cases, useful contributions to the art, many systems include inherent drawbacks. Hemodialysis, in general, is more expensive, more complex, and more difficult to employ than is hemofiltration. Specifically, where a dialysis unit is used to remove waste from a physiological fluid stream and the stream is being re-introduced into a patient, a relatively large volume of dialysate typically is required to create a continuous passage against the side of the dialyzer semipermeable membrane opposite the side addressed physiological fluid. Since the dialysate must be pure to the extent that it is free of chlorine, fluorine, and other poisonous ions that can cross a semipermeable membrane, significant effort is required to produce the necessary volume of purified water.
In many continuous hemofiltration systems ultrafiltrate waste must be replaced by infusate, which often is provided as a fluid for direct introduction into the patient, for example by being introduced into a conduit returning cleansed blood to a patient. In this instance pure, sterile infusate is required, adding complication and cost.
Most man-made renal function systems are not designed for convenient home use. In general, artificial renal treatment is given in a clinical outpatient setting for reasons of safety, since factors such as fluid balance and equipment complexity are critical. Of course, loss of a threshold amount of blood results in death. However, since victims of renal failure treated by man-made renal function systems must spend a significant amount of time undergoing dialysis therapy, these patients must spend a significant amount of time out of their homes if treated in a clinical setting.
Accordingly, it is a general object of the present invention to provide a blood treatment system which is simple to use that does not requires neither the generation of a large volume of pure dialysate solution, nor provision of a sterile replacement infusate formulation.
SUMMARY OF THE INVENTION
The invention includes, in one aspect, a method of purifying bloodstream waste, for the purpose of replacing kidney function, and in another aspect involves forming an infusate solution suitable for introduction into a patient from sterile or non-sterile infusate concentrates. In another aspect of the invention, a system or systems are provided for performing the above functions.
Specifically, in one aspect of the invention, a method is provided for purifying blood stream waste and forming a forming an infusate. Bloodstream waste from a patient is purified to form essentially pure water. A non-sterile infusate additive is sterilized to form a patient-sterile infusate additive, and the essentially pure water, derived from the patient's blood stream waste, is combined with the patient-sterile additive to form an infusate solution suitable for introduction into the blood stream of the patient.
In some embodiments, the bloodstream waste is purified into essentially pure water by subjecting the bloodstream waste to reverse osmosis to remove uremic toxins, with or without a recycle loop. In another embodiment, the blood stream waste is purified by distillation or exposure to a sorbent. In some embodiments, the bloodstream waste is produced by continuously drawing blood from a patient and subjecting the blood to a purification step, such as hemofiltration, to separate the bloodstream waste from cleansed blood. In other embodiments, the bloodstream waste comprises peritoneal dialysate. In some embodiments of the experiment, the infusate solution is prepared by contacting the essentially pure water, derived from bloodstream waste, with a patient-sterile side of a semi-permeable membrane while simultaneously contacting a nonsterile additive with the opposite side of the membrane, thus allowing the additive to be sterilized while passing through the membrane to form the infusate solution. In certain embodiments of the invention, the infusate solution is combined with the cleansed blood and continuously reinfused into the patient.
Another aspect of the invention involves dialyzing a nonsterile infusate additive into a fluid across a semi-permeable membrane. Net ionic flow across the membrane into the fluid occurs thus creating an infusate solution suitable for introduction into a patient without further treatment.
Yet another aspect involves combining a fluid infusate output from a unit containing a semi-permeable membrane with fluid output from a blood purification device to form an infusate soluti
Brugger James M
Burbank Jeffrey H
Finch C David
Bianco P. M.
NStage Medical, Inc.
Proskauer Rose LLP
Sykes Angela D.
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