Method and apparatus for performing peritoneal dialysis

Surgery – Means for introducing or removing material from body for... – Material introduced into and removed from body through...

Reexamination Certificate

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C604S407000

Reexamination Certificate

active

06228047

ABSTRACT:

RELATED APPLICATION
This application is a continuation-in-part of U.S. patent application Ser. No. 09/122,692 filed Jul. 27, 1998, now abandoned, and entitled “METHOD AND APPARATUS FOR PERFORMING PERITONEAL DIALYSIS”.
BACKGROUND OF THE INVENTION
Unlike the extra corporeal system used in hemodialysis (HD) to treat end stage renal disease (ESRD), PD makes use of the internal peritoneal membrane to purify the blood of ESRD patients. The two modalities for carrying out PD are automated peritoneal dialysis (APD) and the manual non-automated procedure of continuous ambulatory peritoneal dialysis (CAPD). According to the latter method, dialysis fluid is exchanged from four to six times throughout the day, every day. The fluid remains inside the patient for about four hours between exchanges and for a much longer period (10-12 hours) at night.
It has become conventional to refer to the basic stages of the PD procedure as F
ILL
, D
WELL
and D
RAIN
. In the F
ILL
, stage, dialysate is instilled through a catheter into the peritoneal cavity of a patient.
During the fixed time period known as the D
WELL
, the dialysate draws soluble waste and excess fluid from blood contained in numerous blood vessels of the peritoneal membrane, by the operation of osmosis and diffusion. Additionally, the dialysate re-balances the electrolyte concentration and corrects for acidosis of the blood.
At the end of the D
WELL
, spent dialysate is removed from the peritoneal cavity (D
RAIN
) and discarded. This exchange action must be repeated several times over a twenty-four hour period, as the body continuously produces waste products.
Compared with HD, PD is a very gentle modality, its slow corrective action resembling that of the natural kidney. It is operationally simple, eliminates the need for venipunctures and has low operational costs. Because the system is not an extracorporeal one, there is no need for a high degree of heparinization, a factor which is especially important in the case of diabetic patients.
However, to date HD has continued to dominate in the treatment of ESRD patients. The following aspects of PD may be contributing factors to this state of affairs:
In PD, the peritoneal membrane is exposed to the external environment every time a catheter is connected or disconnected from the solution supply, making infection (peritonitis) a significant problem.
Currently available commercial dialysate for PD exhibits a low pH which is not truly compatible with the biochemistry of the peritoneal membrane. Consequently this bio-incompatibility is believed to be one of the factors which eventually degrades the performance of the membrane with time.
The most popular osmotic agent used in PD dialysates is glucose. Glucose can be absorbed by the body via the peritoneum membrane. This can result in patient obesity and its accompanying complications. Moreover, heat sterilization of the dialysate which contains glucose produces harmful glucose by-products.
Current techniques of PD afford no ability to monitor the pressure build-up in the peritoneum during either DWELL or during the FILL sequence.
Current PD solutions are of fixed composition and cannot be systematically adjusted either in their constituent parts or in the concentration of each constituent during a treatment.
A number of examples of more or less automated peritoneal dialysis machines are to be found in the art, which may be classified into “continuous cycle” PD systems and “batch” PD systems.
In continuous cycle systems, exemplified by U.S. Pat. Nos. 5,004,459 (Peabody et al.) and 5,643,201 (Peabody et al.), the aforementioned DWELL time is essentially zero. Dialysate is delivered by injection into the peritoneal cavity of a patient, simultaneously with the removal of fluid, in a flow-through process.
Continuous cycle processing employs a great amount of dialysis fluid, making it prohibitively expensive for chronic treatment. Known continuous cycle PD systems rely upon the on-site generation of dialysis fluids employing a reverse osmosis water purification unit (connected to an outside water source), and a dialysate proportioning unit, each such unit being about the size of a normal portable household refrigerator. The apparatus is relatively complex, the fluid proportioning itself often comprising more than two independent pumps with fixed proportioning ratios. This leads to difficulties in operation which are complicated by the need for sterilization procedures and pre- and post-sterilization safety tests.
Applications of continuous flow PD systems are limited to treatment of chronic patients, two or three times per week, with the assistance of a competent helper. The intermittent treatment schedule does not provide adequate PD treatment for a number of chronic patients, particularly those exhibiting little or no residual kidney functions. Hence, this type of PD system has fallen almost entirely into disuse.
Known systems for carrying out batch processing, in which there is an appreciable DWELL time during which the effective dialysis step occurs, are exemplified by U.S. Pat. No. 4,096,859 (Agarwal et al.); U.S. Pat. No. 5,141,492 (Dadson et al.); U.S. Pat. No. 5,324,422 (Colleran et al.); and U.S. Pat. No. 5,348,510 (Bryant et al.).
In a continuing effort to provide adequate PD treatment for the varied population of ESRD patients, clinicians have developed a number of different forms of the APD modality of treatment using batch-type PD systems. These include the APD modalities of:
(i) Continuous Cycling Peritoneal Dialysis (CCPD), a method of performing PD in which an automated cycler performs 4 to 6 regular exchanges every night.
(ii) Intermittent Peritoneal Dialysis (IPD), a method of performing PD in hospitals or at home with an automatic cycler two or three times a week for a period of about eight to twenty hours each time.
(iii) Nightly Peritoneal Dialysis (NPD), a method of performing nightly peritoneal dialysis at home for patients with high efficiency peritoneal membranes. Such patients do not fare well with long dialysate D
WELL
times.
(iv) Tidal Peritoneal Dialysis (TPD). This modality utilizes an initial maximum dialysate fill volume (usually three litres) and periodically, during a long and continuous D
WELL
time, drains a fraction of the fill volume (usually one third, the tidal volume) and re-infuses about a similar amount, adjusting for ultrafiltration (excess fluid removed from the patient's body during kidney dialysis) into the patient.
However, even the existing batch-type systems have not proven to be entirely satisfactory in addressing real clinical concerns and implementing the above-listed PD modalities effectively. Some of the major limitations presented by existing systems are:
(i) The low pH of the current commercially available dialysate that is not bio-compatible with the peritoneal membrane (reduces the efficiency of the membrane with time).
(ii) Excessive glucose absorption by the patient (glucose is the most popular osmotic agent).
(iii) Harmful by-products of glucose produced during heat sterilization of the dialysate (adverse to the peritoneal membrane and therefore shortens PD lifetime).
(iv) Excessive pressure build-up in the peritoneum during DWELL period (damage to the peritoneal membrane—hernias and leaks).
(v) Inability to monitor the ultrafiltration (UF) rates on-line to determine the effects of medications on the solute transport (vessel dilators or constrictors leading to higher or lower membrane transports respectively), and profoundly affecting adequacy of treatment.
(vi) Lack of any provision for regulating osmotic concentrations or alternating different osmotic agents during treatment (to optimize solute removal).
(vii) Lack of accessories to automatically add accurate dosage of medication on-line to patient during treatment (advantage to children, to diabetics, to geriatrics and, reduction of contamination).
General Description of the Invention
Applicant's overall objective was to provide an automated peritoneal dialysis machine capable of fully “customizing” the composition of di

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