CA2303714C - Multifunctional apparatus for treatment of renal insufficiency - Google Patents
Multifunctional apparatus for treatment of renal insufficiency Download PDFInfo
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- CA2303714C CA2303714C CA002303714A CA2303714A CA2303714C CA 2303714 C CA2303714 C CA 2303714C CA 002303714 A CA002303714 A CA 002303714A CA 2303714 A CA2303714 A CA 2303714A CA 2303714 C CA2303714 C CA 2303714C
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Abstract
A multifunction apparatus for circulating corporeal and medical liquids in a membrane exchanger (1) comprises:
- first pumping means (12) for circulating a first sterile liquid;
- second pumping means (22) for circulating a second sterile liquid;
- third pumping means (6, 26) for circulating blood in an extracorporeal blood circuit (5, 7, 8) connected to a first compartment (2) of the exchanger (1);
- extraction means (19, 26) for causing ultrafiltration of a corporeal liquid through the membrane (4) of the exchanger (1);
- first weighing means (23 ; 27, 28) for weighing a first reservoir (10) for the first sterile liquid, and a second reservoir (17) for a waste liquid, the first reservoir (10) being connectable to an inlet of a second compartment (3) of the exchanger, and the second reservoir (17) being connectable to an outlet of the second compartment (3) of the exchanger (1);
- second weighing means (24) for weighing a third reservoir (20) for the second sterile liquid, this reservoir being connectable to the extracorporeal blood circuit (5, 7, 8); and - control means (25) for receiving at least weight information from the first weighing means (23 ; 27, 28) and the second weighing means (24) and for controlling at least one of the first, the second and the third pumping means (22, 12, 6, 26) and the extraction means (19, 26), from at least this weight information and from at least one information corresponding to a desired flow rate of at least one of the first sterile liquid, the second sterile liquid, the blood and the corporeal liquid.
- first pumping means (12) for circulating a first sterile liquid;
- second pumping means (22) for circulating a second sterile liquid;
- third pumping means (6, 26) for circulating blood in an extracorporeal blood circuit (5, 7, 8) connected to a first compartment (2) of the exchanger (1);
- extraction means (19, 26) for causing ultrafiltration of a corporeal liquid through the membrane (4) of the exchanger (1);
- first weighing means (23 ; 27, 28) for weighing a first reservoir (10) for the first sterile liquid, and a second reservoir (17) for a waste liquid, the first reservoir (10) being connectable to an inlet of a second compartment (3) of the exchanger, and the second reservoir (17) being connectable to an outlet of the second compartment (3) of the exchanger (1);
- second weighing means (24) for weighing a third reservoir (20) for the second sterile liquid, this reservoir being connectable to the extracorporeal blood circuit (5, 7, 8); and - control means (25) for receiving at least weight information from the first weighing means (23 ; 27, 28) and the second weighing means (24) and for controlling at least one of the first, the second and the third pumping means (22, 12, 6, 26) and the extraction means (19, 26), from at least this weight information and from at least one information corresponding to a desired flow rate of at least one of the first sterile liquid, the second sterile liquid, the blood and the corporeal liquid.
Description
MULTIFUNCTIONAL APPARATUS FOR TREATMENT
OF RENAL INSUFFICIENCY
The present invention is a division of the Canadian patent application 2,077,848 filed on September 9, 1992.
The present invention relates to an apparatus enabling to put on to different types of treatment patients suffering from kidney failure, in particular following an accident or a surgical operation.
In addition, the invention relates to an apparatus enabling the accurate dosage in blood of substances such as medicines ( i n particular antibiotics), glucose, or certain blood electrolytes (potassium, magnesium; and bicarbonate, in particular). The invention is described below in its application to dosing bicarbonate, but i t will be understood that this particular example is given purely by way of illustration and is not limiting in any way.
2o It is known that in addition to purifying plasma wastes (urea, creatinine) and to excreting water, the kidneys play an important part in maintaining the acid-base equilibrium of the internal medium, i n particular by eliminating weak acids (phosphates, monosodium acids) and by producing ammonium salts.
In people who have lost their kidney function either temporarily or permanently, because this regulating mechanism is no longer operating, an increase is observed in the acidity of the internal medium (acidosis), i.e. a drop in the pH of the blood serum towards 7 30 (where blood pH normally lies within the very narrow limits of 7.35 to 7.45).
The conventional way of mitigating this deficiency of the 1a regulating mechanism of the kidneys is to act on another mechanism for regulating the acid-base equilibrium of the internal medium, which mechanism is constituted by buffer systems of the blood, and the main such system comprises carbonic acid as a weak acid i n association with its alkaline salt, bicarbonate. Thus, to combat the acidosis of a person suffering from kidney failure, bicarbonate i s caused to pass into the blood, generally simultaneously with a session during which the blood is purified by hemofiltration or by hemodialysis.
During treatment by hemofiltration, where blood is purified by ultrafiltration of plasma water through a semi permeable membrane accompanied by convective transfer of plasma wastes, bicarbonate i s added by infusing a solution of sodium bicarbonate.
During hemodialysis treatment where blood is purified by plasma wastes being transferred by diffusion through a semipermeable membrane with blood being circulated on one face o f the membrane and a dialysis liquid being circulated on the other face, bicarbonate may be added in two ways, depending on whether the dialysis liquid contains bicarbonate or whether it has none.
When the dialysis liquid contains bicarbonate, then bicarbonate is added to the blood by diffusion from the dialysis liquid through the semipermeable membrane into the blood, and the bicarbonate concentration in the dialysis liquid is adjusted accordingly.
When the dialysis liquid does not contain bicarbonate, then a solution of sodium bicarbonate is infused into the patient as during hemofiltration treatment, and in sufficient quantity to compensate for the diffusive losses (or the convective losses in hemofiltration) that occur in the membrane exchanger and to compensate for the deficit from which the patient in an acidosis state is suffering.
The final concentration of bicarbonate in the blood of a patient subjected to either of these treatments depends on the concentration of bicarbonate in the infusion solution or in the dialysis liquid, on the respective flow rates thereof, and on the flow rate of the patient's blood through the membrane exchanger. With the exception of the concentration of the sodium bicarbonate solution which is fixed by the manufacturer, these parameters are, at present, determined empirically by the doctor on the basis of blood pH measurements that are performed regularly for such patients in a state of shock, whose blood is being dialyzed or ultrafiltered on a permanent basis, or as performed after one treatment session and before the following session for patients who have lost kidney function permanently. I t results therefrom that the concentration of bicarbonate in the blood of the patient seldom corresponds to the desired concentration.
An object of the invention is to provide a blood treatment apparatus which is particularly suited to continuously carry out a plurality of treatments, and which enables an accurate control and monitoring of the flow rates of the medical and corporeal liquids which are circulated.
According to the invention, this object is achieved by a multifunction apparatus for circulating corporeal and medical liquids in an exchanger having two compartments separated by a semipermeable membrane, a first compartment being connected to an extracorporeal blood circuit connectable to a patient, and a second compartment having an inlet and an outlet, the apparatus comprising:
~ first pumping means for circulating a first sterile liquid;
~ second pumping means for circulating a second sterile liquid;
~ ~ third pumping means for circulating blood in the extracorporeal blood circuit;
~ extraction means for causing ultrafiltration of a corporeal liquid through the membrane of the exchanger;
~ first weighing means for weighing a first reservoir for the first sterile liquid, and a second reservoir for a waste liquid, the first reservoir being connectable to the inlet of the second compartment of the exchanger, and the second reservoir being connectable to the outlet of the second compartment of the exchanger;
~ second weighing means for weighing a third reservoir for the second sterile liquid, this reservoir being connectable to the S extracorporeal blood circuit; and ~ control means for receiving at least weight information fro m the first weighing means and the second weighing means and for controlling at least one of the first, the second and the third pumping means and the extraction means, from at least this weight information and from at least one information corresponding to a desired flow rate of at least one of the first sterile liquid, the second sterile liquid, the blood and the corporeal liquid.
The first weighing means includes either two independent weighing means for weighing the first reservoir and the second reservoir respectively, or a single weighing means for weighing both the first reservoir and the second reservoir.
According to a characteristic of the invention, the apparatus further comprises connecting means for permitting the f i r s t reservoir to be selectively connectable to the inlet of the second compartment of the exchanger or to the extracorporeal blood circuit.
According to another characteristic of the invention, the apparatus further comprises dosage means for adjusting to a desired concentration [A]DES, in the blood of the patient, the concentration o f a substance (A) present in the second sterile liquid, whereby the diffusive and/or convective transfer of the substance (A) through the membrane of the exchanger is taken into account According to a variant of the invention, the dosage means comprises means for regulating the flow rate (QA) of the second sterile liquid as a function of the flow rate (Qour) of the waste liquid, whereby the flow rate (QA) of the second sterile liquid and the flow rate (QouT) of the waste liquid are related by the equation:
QA - [A]DES x QoUT
[A]soy where [A]SOS is the of the substance (A) in concentration the f i r s t sterile liquid.
According to another variantof the invention, the means dosage comprises means for regulatingthe flow rate (QA) of second the sterile liquid function of clearance CI of the artificialkidney as a the for the substance (A), whereby the flow rate (QA) of second the sterile liquid and the clearance are related by the equation:
CI
[A]DES x CI
OA [A]sou where [A]soy is the concentration of the substance (A) in the f i r s t sterile liquid.
Other characteristics and advantages of the invention appear on reading the following description. Reference is made to the accompanying drawings, in which:
Figure 1 is a simplified diagram of a first embodiment of the invention; and Figure 2 is a simplified diagram of a second embodiment of the invention.
The artificial kidney shown in Figure 1 comprises an exchanger 1 having two compartments 2 and 3 separated by a semipermeable membrane 4. The compartment 2 is connected to a circuit for extracorporeal blood circulation and comprising an upstream duct 5 having a circulation pump 6 disposed thereon, and a downstream duct 7 fitted with a bubble trap 8. The ducts 5 and 7 have their free ends provided with respective needles or catheter connectors f o r connecting the circuit for extracorporeal blood circulation to the vascular system of a patient 9.
A container 10 containing sterile substitution/dialysis liquid that does not contain any bicarbonate is connected via common length of duct 11 which has a circulation pump 12 disposed thereon to two ducts 13 and 14 that are connected respectively to the bubble trap 8 and to an inlet of the second compartment 3 of the exchanger 1.
Blocking means 15 and 16 such as electromagnetically-operated clamps are provided on the ducts 13 and 14 respectively to enable the container 10 to be isolated or connected selectively to the exchanger 1 or to the circuit for extracorporeal blood circulation.
A second container 17 for waste liquid (ultrafiltrate and/or waste dialysis liquid) is connected to an outlet of the second compartment 3 of the exchanger 1 by a duct 18 which has an extraction pump 19 for the waste liquid disposed thereon. The pump 19 serves to establish a variable pressure drop in the compartment 3 of the exchanger 1, i.e. it serves to vary the transmembrane pressure and consequently the ultrafiltration flow rate.
A third container 20 containing a sterile solution of sodium bicarbonate is connected to the bubble trap 8 by means of a duct 21 which has a circulation pump 22 disposed thereon.
In accordance with the invention, the artificial kidney shown i n Figure 1 includes means for measuring the difference between the liquids) infused into the patient 9 and the waste liquid, optionally for determining a desired weight loss to be achieved by extracting a quantity of plasma water that is greater than the quantity of infused liquid(s), and to establish a determined value of bicarbonate concentration in the plasma of the patient. These means comprise first scales 23 for weighing the container 10 o f substitution/dialysis liquid and the container 17 of waste liquid, second scales 24 for weighing the container 20 of sodium bicarbonate solution, and a control unit 25 suitable for receiving the data delivered by the scales 23 and 24 as input signals, a reference value QW~ for the desired weight loss flow rate, the value [HC03]SOS of the concentration of bicarbonate in the solution contained in the container 20, and a reference value [HC4s]pES for the desired concentration of bicarbonate in the blood. The control unit 25 i s designed to control the waste liquid extraction pump i 9 taking into account the desired weight loss QW~ and the flow rate Q~N imposed on the pump 12 for circulating the substitution/dialysis liquid, and t o control the pump 22 for infusing the bicarbonate solution taking into account the flow rate QpuT of the waste liquid extraction pump 19.
In accordance with the invention, the flow rate C~pa of the infusion pump 22 can be controlled as a function of the flow rate Qpu'r of the extraction pump 19 regardless of the type of treatment being delivered to the patient (hemofiltration with or without infusion o f substitution liquid, hemodialysis, or hemodiafiltration) by the equation:
~co3 = QouT x~C~IoES (1 ) [HC03Jso~
The above-described artificial kidney operates as follows:
In hemofiltration mode without any substitution liquid being infused, the clamps 15 and 16 are closed, the pump 12 for circulating g the substitution/dialysis liquid is off, and the pumps 19 and 22 for extracting the blood filtrate and the infusion of bicarbonate solution are on. The control unit 25 continuously adjusts the flow rate QpuT of the extraction pump 19 as measured by means of the scales 23 so that the flow rate is permanently equal to the sum of the desired weight loss flow rate QWL and the flow rate Q~pa of the infusion o f bicarbonate solution as measured by means of the scales 24. The control unit 25 also continuously adjusts the flow rate C~pa of the pump 22 for infusing the bicarbonate solution as a function of the desired concentration of bicarbonate [HC03]pES in the blood of the patient, of the concentration [HC03]soL of the solution contained i n the container 20, and of the connective losses that occur in the exchanger 1, which losses are equal to C~n- x [QHCOa]BLD~ where [QHCO3]BLD is the concentration of bicarbonate in the blood of the patient, and where the transmittance of the high permeability membranes used for hemofiltration is equal to 1 for blood electrolytes (recall that the general formula giving the mass f I ow rate Js of a substance passing through a membrane as a function o f the volume flow rate Jv of plasma water is the following:
Js = Jv x Tr x Cs where Cs is the concentration of the substance in the blood and where Tr is the transmittance of the membrane relative to said substance).
The pump 22 for infusing the bicarbonate solution being servo-controlled in compliance with equation (1) given above enables thus the blood of the patient 9 to be brought progressively to an equilibrium state where its concentration of bicarbonate is equal to [HC~3] DES
In hemofiltration mode with infusion of substitution liquid, the clamp 16 is closed, the clamp 15 is open and all three pumps 12, 19, and 22 are on, with the flow rate of the pump 12 being fixed by the operator to a constant value at the beginning of a treatment session.
The operation of the artificial kidney in this second treatment mode differs from that described above only in that to control the S extraction pump 19 the control unit 25 takes account of the emptying of the container 10, with the flow rate ~ imposed on the pump 1 9 then being selected so that the difference between the flow rate o f substitution liquid and the flow rate of waste liquid as measured by the scale 23 is equal to the sum of the desired weight loss flow rate QW~ and the infusion rate C~o3 of bicarbonate solution as measured by the scales 24. The infusion pump 22 for the bicarbonate solution is adjusted as before in compliance with the servo-control specified by equation (1 ).
In hemodialysis mode, the clamp 15 is closed, the clamp 16 i s open, and all three pumps 12, 19 and 22 are on. The control unit 25 continuously adjusts the flow rate QouT of the extraction pump 19 so that the difference between the flow rate of dialysis liquid and the flow rate of waste liquid as measured by the scales 23 i s continuously equal to the infusion flow rate C~-~~ of bicarbonate solution as measured by the scales 24, with the weight loss f I o w rate reference value being zero.
The control unit 25 also controls the infusion flow rate QHCO3 of the bicarbonate solution as a function of the desired bicarbonate concentration [HC03]pES for the blood of the patient, of the concentration [HC03Jso~ of the solution contained in the container 20, and of the diffusive loss through the exchanger 1 which is given by CI
x [HC03]gLD, where [HC03]gLD is the concentration of bicarbonate i n the blood of the patient and where CI is the clearance of th a artificial kidney for bicarbonate (the clearance is defined in general 1 ~
terms as the ratio between the quantity of substance eliminated per unit time and the concentration of the substance in the blood at the inlet of the exchanger). To ensure that the concentration o f bicarbonate in the blood reaches a given value [HC03]pES a t equilibrium, it is therefore necessary to control the infusion f I o w rate QHCO3 of the pump 22 for the bicarbonate solution in compliance with the equation:
(HC~3~DES
QHC03 = CI X ~C~~SOL
which assumes that the clearance of the artificial kidney has previously been determined, which clearance depends on the type o f exchanger used (nature of the membrane, area) and, in general, on the flow rates of blood and of dialysis liquid through the exchanger.
However, for certain values of blood flow rate and of dialysis liquid flow rate, the clearance of the kidney for a given substance and a given type of exchanger is substantially constant. This applies i n particular when firstly the area of the membrane in the exchanger i s sufficiently large relative to the blood flow rate and secondly the blood flow rate is relatively large compared with the dialysis liquid flow rate (being about three or more times said rate). Under such circumstances, the blood and the dialysis liquid leaving the exchanger have the same concentration of the substance under consideration and the clearance CI is equal to the outlet flow rate of the waste liquid QOUT. In other words, under these particular operating conditions, the control of the pump 22 for infusing the bicarbonate solution i s defined by equation (1). These conditions are applicable to continuous dialysis treatment of patients in a state of shock for whom purification must be performed at a moderate rate so that their weakened organism can tolerate it.
The artificial kidney of the invention thus has a particular advantage for treating patients who have temporarily lost kidney function since, whatever the type of treatment to which they are subjected, this artificial kidney makes it possible to act on th a i r S acid-base equilibrium in a manner that is simple by controlling one pump only using a single servo-control equation.
The kidney can also operate in hemodiafiltration mode in which the positions of the clamps and the operation of the pumps are the same as in hemodialysis mode, except that the pump 19 is controlled so as to give rise to ultrafiltration in the kidney in compliance with a given reference value for weight loss rate.
The artificial kidney shown in Figure 2 differs from that described above in that its circuit for extracorporeal blood circulation includes a second pump 26 disposed downstream from the exchanger 1, thereby enabling the transmembrane pressure in th a exchanger 1 to be varied and consequently enabling the flow rate o f ultrafiltered plasma water to be varied (i.e. Caps in hemofiltration).
In addition, the containers 10 and 17 for the substitution/dialysis and for the waste liquid are now weighed by independent scales 27, 28, and the duct 18 connecting the compartment 3 of the exchanger 1 to the waste liquid container 17 is not provided with a pump.
Moreover, a three-port valve 29 having the ducts 11, 13, and 14 connected thereto serves to connect the container 10 for the substitution/dialysis liquid either to the bubble trap 8 or to the compartment 3 of the exchanger 1, or else to isolate the container 10.
The operation of this second embodiment of the art i f i c i a l kidney of the invention is not significantly different from that of the preceding embodiment. In hemofiltration mode without infusion o f substitution liquid, the pump 12 is off and the flow rate of the pump 26 is controlled by the control unit 25 so that the filtration flow rate ~ measured by the scales 28 is equal to the sum of the reference weight loss flow rate QW~ and the infusion flow rate o f bicarbonate solution QHCO3 as measured by the scales 24.
In hemofiltration mode with infusion of substitution liquid, the pump 12 is on at a rate that is initially adjusted by the operator, and the rate of the pump 26 is controlled by the control unit 25 so that the filtration rate C~~ is equal to the sum of the reference weight loss rate Qw~, the infusion rate of bicarbonate solution QHC03~ and the infusion rate Q~N of substitution liquid as measured by the scales 27.
In dialysis mode, the pumps 6 and 26 on the blood c i rcu it respectively upstream and downstream from the exchanger 1 operate at the same rate, and the pump 12 which then serves as a pump f o r circulating the dialysis liquid operates at a rate that is set i n i t i a I I
y by the operator.
In hemodiafiltration mode, the control unit 25 controls the f I o w rate of the ~~pump 26 as in hemofiltration mode with infusion o f substitution liquid.
Except for hemofiltration mode in which the pump is off, the flow rate of the pump 12 for circulating the substitution/dialysis liquid is controlled by the control unit 25 which compares the desired flow rate stored initially in the memory of said unit with the flow rate as measured by the scales 27. The flow rate (spa of the pump 22 for infusing bicarbonate is controlled, as before, as a function o f the waste liquid flow rate r~ as measured by the scales 28, i n compliance with equation (1 ), or equation (2), as the case may be.
The invention is not limited to the embodiments described above and variants may be provided.
In particular, in contrast to the artificial kidney embodiments described above, in modes where the substitution/dialysis liquid i s circulated by the pump 12, it is possible to have the flow rate of the pump 19 (26) that controls the ultrafiltration flow rate as the rate that is fixed initially by the operator, with the flow rate of the pump 12 being controlled as a function of the difference between the fresh liquids and the waste liquids as infused and ultrafiltered, and the desired weight loss rate.
Moreover, the value of the liquid flow rates needed for controlling the pump 19 (26) controlling the ultrafiltration flow rate and for controlling the pump 22 for infusing the bicarbonate solution could be determined by measurement means other than scales, f o r example using flow rate meters or volume-measuring means.
Moreover, the pumps 12 and 22 used for controlling the f I ow rate of substitution/dialysis liquid and the flow rate of bicarbonate solution could be replaced by electromagnetically-operated clamps, with the liquids then flowing under gravity.
Also the source 10 of infusion liquid could be directly connected to the vascular system of the patient and not, as described before, to the circuit 5, 7 for extracorporeal blood circulation.
Finally, as mentioned above, the dosage means fitted to an artificial kidney of the invention may be used for dispensing all sorts of substances into the blood of a patient undergoing a treatment session by hemofiltration, hemodialysis, or hemodiafiltration. For a medicine A, for example, the container 20 would contain a sterile solution of the medicine with the container 10 containing a dialysis liquid in which the main electrolytes of blood are present, including bicarbonate. The operation of the kidney is not different from that described above with reference to the embodiments of Figures 1 and 2, and in particular, the infusion pump 22 is controlled as a function of the flow rate of waste liquid in application of equation (1 ) o r equation (2) as the case may be.
OF RENAL INSUFFICIENCY
The present invention is a division of the Canadian patent application 2,077,848 filed on September 9, 1992.
The present invention relates to an apparatus enabling to put on to different types of treatment patients suffering from kidney failure, in particular following an accident or a surgical operation.
In addition, the invention relates to an apparatus enabling the accurate dosage in blood of substances such as medicines ( i n particular antibiotics), glucose, or certain blood electrolytes (potassium, magnesium; and bicarbonate, in particular). The invention is described below in its application to dosing bicarbonate, but i t will be understood that this particular example is given purely by way of illustration and is not limiting in any way.
2o It is known that in addition to purifying plasma wastes (urea, creatinine) and to excreting water, the kidneys play an important part in maintaining the acid-base equilibrium of the internal medium, i n particular by eliminating weak acids (phosphates, monosodium acids) and by producing ammonium salts.
In people who have lost their kidney function either temporarily or permanently, because this regulating mechanism is no longer operating, an increase is observed in the acidity of the internal medium (acidosis), i.e. a drop in the pH of the blood serum towards 7 30 (where blood pH normally lies within the very narrow limits of 7.35 to 7.45).
The conventional way of mitigating this deficiency of the 1a regulating mechanism of the kidneys is to act on another mechanism for regulating the acid-base equilibrium of the internal medium, which mechanism is constituted by buffer systems of the blood, and the main such system comprises carbonic acid as a weak acid i n association with its alkaline salt, bicarbonate. Thus, to combat the acidosis of a person suffering from kidney failure, bicarbonate i s caused to pass into the blood, generally simultaneously with a session during which the blood is purified by hemofiltration or by hemodialysis.
During treatment by hemofiltration, where blood is purified by ultrafiltration of plasma water through a semi permeable membrane accompanied by convective transfer of plasma wastes, bicarbonate i s added by infusing a solution of sodium bicarbonate.
During hemodialysis treatment where blood is purified by plasma wastes being transferred by diffusion through a semipermeable membrane with blood being circulated on one face o f the membrane and a dialysis liquid being circulated on the other face, bicarbonate may be added in two ways, depending on whether the dialysis liquid contains bicarbonate or whether it has none.
When the dialysis liquid contains bicarbonate, then bicarbonate is added to the blood by diffusion from the dialysis liquid through the semipermeable membrane into the blood, and the bicarbonate concentration in the dialysis liquid is adjusted accordingly.
When the dialysis liquid does not contain bicarbonate, then a solution of sodium bicarbonate is infused into the patient as during hemofiltration treatment, and in sufficient quantity to compensate for the diffusive losses (or the convective losses in hemofiltration) that occur in the membrane exchanger and to compensate for the deficit from which the patient in an acidosis state is suffering.
The final concentration of bicarbonate in the blood of a patient subjected to either of these treatments depends on the concentration of bicarbonate in the infusion solution or in the dialysis liquid, on the respective flow rates thereof, and on the flow rate of the patient's blood through the membrane exchanger. With the exception of the concentration of the sodium bicarbonate solution which is fixed by the manufacturer, these parameters are, at present, determined empirically by the doctor on the basis of blood pH measurements that are performed regularly for such patients in a state of shock, whose blood is being dialyzed or ultrafiltered on a permanent basis, or as performed after one treatment session and before the following session for patients who have lost kidney function permanently. I t results therefrom that the concentration of bicarbonate in the blood of the patient seldom corresponds to the desired concentration.
An object of the invention is to provide a blood treatment apparatus which is particularly suited to continuously carry out a plurality of treatments, and which enables an accurate control and monitoring of the flow rates of the medical and corporeal liquids which are circulated.
According to the invention, this object is achieved by a multifunction apparatus for circulating corporeal and medical liquids in an exchanger having two compartments separated by a semipermeable membrane, a first compartment being connected to an extracorporeal blood circuit connectable to a patient, and a second compartment having an inlet and an outlet, the apparatus comprising:
~ first pumping means for circulating a first sterile liquid;
~ second pumping means for circulating a second sterile liquid;
~ ~ third pumping means for circulating blood in the extracorporeal blood circuit;
~ extraction means for causing ultrafiltration of a corporeal liquid through the membrane of the exchanger;
~ first weighing means for weighing a first reservoir for the first sterile liquid, and a second reservoir for a waste liquid, the first reservoir being connectable to the inlet of the second compartment of the exchanger, and the second reservoir being connectable to the outlet of the second compartment of the exchanger;
~ second weighing means for weighing a third reservoir for the second sterile liquid, this reservoir being connectable to the S extracorporeal blood circuit; and ~ control means for receiving at least weight information fro m the first weighing means and the second weighing means and for controlling at least one of the first, the second and the third pumping means and the extraction means, from at least this weight information and from at least one information corresponding to a desired flow rate of at least one of the first sterile liquid, the second sterile liquid, the blood and the corporeal liquid.
The first weighing means includes either two independent weighing means for weighing the first reservoir and the second reservoir respectively, or a single weighing means for weighing both the first reservoir and the second reservoir.
According to a characteristic of the invention, the apparatus further comprises connecting means for permitting the f i r s t reservoir to be selectively connectable to the inlet of the second compartment of the exchanger or to the extracorporeal blood circuit.
According to another characteristic of the invention, the apparatus further comprises dosage means for adjusting to a desired concentration [A]DES, in the blood of the patient, the concentration o f a substance (A) present in the second sterile liquid, whereby the diffusive and/or convective transfer of the substance (A) through the membrane of the exchanger is taken into account According to a variant of the invention, the dosage means comprises means for regulating the flow rate (QA) of the second sterile liquid as a function of the flow rate (Qour) of the waste liquid, whereby the flow rate (QA) of the second sterile liquid and the flow rate (QouT) of the waste liquid are related by the equation:
QA - [A]DES x QoUT
[A]soy where [A]SOS is the of the substance (A) in concentration the f i r s t sterile liquid.
According to another variantof the invention, the means dosage comprises means for regulatingthe flow rate (QA) of second the sterile liquid function of clearance CI of the artificialkidney as a the for the substance (A), whereby the flow rate (QA) of second the sterile liquid and the clearance are related by the equation:
CI
[A]DES x CI
OA [A]sou where [A]soy is the concentration of the substance (A) in the f i r s t sterile liquid.
Other characteristics and advantages of the invention appear on reading the following description. Reference is made to the accompanying drawings, in which:
Figure 1 is a simplified diagram of a first embodiment of the invention; and Figure 2 is a simplified diagram of a second embodiment of the invention.
The artificial kidney shown in Figure 1 comprises an exchanger 1 having two compartments 2 and 3 separated by a semipermeable membrane 4. The compartment 2 is connected to a circuit for extracorporeal blood circulation and comprising an upstream duct 5 having a circulation pump 6 disposed thereon, and a downstream duct 7 fitted with a bubble trap 8. The ducts 5 and 7 have their free ends provided with respective needles or catheter connectors f o r connecting the circuit for extracorporeal blood circulation to the vascular system of a patient 9.
A container 10 containing sterile substitution/dialysis liquid that does not contain any bicarbonate is connected via common length of duct 11 which has a circulation pump 12 disposed thereon to two ducts 13 and 14 that are connected respectively to the bubble trap 8 and to an inlet of the second compartment 3 of the exchanger 1.
Blocking means 15 and 16 such as electromagnetically-operated clamps are provided on the ducts 13 and 14 respectively to enable the container 10 to be isolated or connected selectively to the exchanger 1 or to the circuit for extracorporeal blood circulation.
A second container 17 for waste liquid (ultrafiltrate and/or waste dialysis liquid) is connected to an outlet of the second compartment 3 of the exchanger 1 by a duct 18 which has an extraction pump 19 for the waste liquid disposed thereon. The pump 19 serves to establish a variable pressure drop in the compartment 3 of the exchanger 1, i.e. it serves to vary the transmembrane pressure and consequently the ultrafiltration flow rate.
A third container 20 containing a sterile solution of sodium bicarbonate is connected to the bubble trap 8 by means of a duct 21 which has a circulation pump 22 disposed thereon.
In accordance with the invention, the artificial kidney shown i n Figure 1 includes means for measuring the difference between the liquids) infused into the patient 9 and the waste liquid, optionally for determining a desired weight loss to be achieved by extracting a quantity of plasma water that is greater than the quantity of infused liquid(s), and to establish a determined value of bicarbonate concentration in the plasma of the patient. These means comprise first scales 23 for weighing the container 10 o f substitution/dialysis liquid and the container 17 of waste liquid, second scales 24 for weighing the container 20 of sodium bicarbonate solution, and a control unit 25 suitable for receiving the data delivered by the scales 23 and 24 as input signals, a reference value QW~ for the desired weight loss flow rate, the value [HC03]SOS of the concentration of bicarbonate in the solution contained in the container 20, and a reference value [HC4s]pES for the desired concentration of bicarbonate in the blood. The control unit 25 i s designed to control the waste liquid extraction pump i 9 taking into account the desired weight loss QW~ and the flow rate Q~N imposed on the pump 12 for circulating the substitution/dialysis liquid, and t o control the pump 22 for infusing the bicarbonate solution taking into account the flow rate QpuT of the waste liquid extraction pump 19.
In accordance with the invention, the flow rate C~pa of the infusion pump 22 can be controlled as a function of the flow rate Qpu'r of the extraction pump 19 regardless of the type of treatment being delivered to the patient (hemofiltration with or without infusion o f substitution liquid, hemodialysis, or hemodiafiltration) by the equation:
~co3 = QouT x~C~IoES (1 ) [HC03Jso~
The above-described artificial kidney operates as follows:
In hemofiltration mode without any substitution liquid being infused, the clamps 15 and 16 are closed, the pump 12 for circulating g the substitution/dialysis liquid is off, and the pumps 19 and 22 for extracting the blood filtrate and the infusion of bicarbonate solution are on. The control unit 25 continuously adjusts the flow rate QpuT of the extraction pump 19 as measured by means of the scales 23 so that the flow rate is permanently equal to the sum of the desired weight loss flow rate QWL and the flow rate Q~pa of the infusion o f bicarbonate solution as measured by means of the scales 24. The control unit 25 also continuously adjusts the flow rate C~pa of the pump 22 for infusing the bicarbonate solution as a function of the desired concentration of bicarbonate [HC03]pES in the blood of the patient, of the concentration [HC03]soL of the solution contained i n the container 20, and of the connective losses that occur in the exchanger 1, which losses are equal to C~n- x [QHCOa]BLD~ where [QHCO3]BLD is the concentration of bicarbonate in the blood of the patient, and where the transmittance of the high permeability membranes used for hemofiltration is equal to 1 for blood electrolytes (recall that the general formula giving the mass f I ow rate Js of a substance passing through a membrane as a function o f the volume flow rate Jv of plasma water is the following:
Js = Jv x Tr x Cs where Cs is the concentration of the substance in the blood and where Tr is the transmittance of the membrane relative to said substance).
The pump 22 for infusing the bicarbonate solution being servo-controlled in compliance with equation (1) given above enables thus the blood of the patient 9 to be brought progressively to an equilibrium state where its concentration of bicarbonate is equal to [HC~3] DES
In hemofiltration mode with infusion of substitution liquid, the clamp 16 is closed, the clamp 15 is open and all three pumps 12, 19, and 22 are on, with the flow rate of the pump 12 being fixed by the operator to a constant value at the beginning of a treatment session.
The operation of the artificial kidney in this second treatment mode differs from that described above only in that to control the S extraction pump 19 the control unit 25 takes account of the emptying of the container 10, with the flow rate ~ imposed on the pump 1 9 then being selected so that the difference between the flow rate o f substitution liquid and the flow rate of waste liquid as measured by the scale 23 is equal to the sum of the desired weight loss flow rate QW~ and the infusion rate C~o3 of bicarbonate solution as measured by the scales 24. The infusion pump 22 for the bicarbonate solution is adjusted as before in compliance with the servo-control specified by equation (1 ).
In hemodialysis mode, the clamp 15 is closed, the clamp 16 i s open, and all three pumps 12, 19 and 22 are on. The control unit 25 continuously adjusts the flow rate QouT of the extraction pump 19 so that the difference between the flow rate of dialysis liquid and the flow rate of waste liquid as measured by the scales 23 i s continuously equal to the infusion flow rate C~-~~ of bicarbonate solution as measured by the scales 24, with the weight loss f I o w rate reference value being zero.
The control unit 25 also controls the infusion flow rate QHCO3 of the bicarbonate solution as a function of the desired bicarbonate concentration [HC03]pES for the blood of the patient, of the concentration [HC03Jso~ of the solution contained in the container 20, and of the diffusive loss through the exchanger 1 which is given by CI
x [HC03]gLD, where [HC03]gLD is the concentration of bicarbonate i n the blood of the patient and where CI is the clearance of th a artificial kidney for bicarbonate (the clearance is defined in general 1 ~
terms as the ratio between the quantity of substance eliminated per unit time and the concentration of the substance in the blood at the inlet of the exchanger). To ensure that the concentration o f bicarbonate in the blood reaches a given value [HC03]pES a t equilibrium, it is therefore necessary to control the infusion f I o w rate QHCO3 of the pump 22 for the bicarbonate solution in compliance with the equation:
(HC~3~DES
QHC03 = CI X ~C~~SOL
which assumes that the clearance of the artificial kidney has previously been determined, which clearance depends on the type o f exchanger used (nature of the membrane, area) and, in general, on the flow rates of blood and of dialysis liquid through the exchanger.
However, for certain values of blood flow rate and of dialysis liquid flow rate, the clearance of the kidney for a given substance and a given type of exchanger is substantially constant. This applies i n particular when firstly the area of the membrane in the exchanger i s sufficiently large relative to the blood flow rate and secondly the blood flow rate is relatively large compared with the dialysis liquid flow rate (being about three or more times said rate). Under such circumstances, the blood and the dialysis liquid leaving the exchanger have the same concentration of the substance under consideration and the clearance CI is equal to the outlet flow rate of the waste liquid QOUT. In other words, under these particular operating conditions, the control of the pump 22 for infusing the bicarbonate solution i s defined by equation (1). These conditions are applicable to continuous dialysis treatment of patients in a state of shock for whom purification must be performed at a moderate rate so that their weakened organism can tolerate it.
The artificial kidney of the invention thus has a particular advantage for treating patients who have temporarily lost kidney function since, whatever the type of treatment to which they are subjected, this artificial kidney makes it possible to act on th a i r S acid-base equilibrium in a manner that is simple by controlling one pump only using a single servo-control equation.
The kidney can also operate in hemodiafiltration mode in which the positions of the clamps and the operation of the pumps are the same as in hemodialysis mode, except that the pump 19 is controlled so as to give rise to ultrafiltration in the kidney in compliance with a given reference value for weight loss rate.
The artificial kidney shown in Figure 2 differs from that described above in that its circuit for extracorporeal blood circulation includes a second pump 26 disposed downstream from the exchanger 1, thereby enabling the transmembrane pressure in th a exchanger 1 to be varied and consequently enabling the flow rate o f ultrafiltered plasma water to be varied (i.e. Caps in hemofiltration).
In addition, the containers 10 and 17 for the substitution/dialysis and for the waste liquid are now weighed by independent scales 27, 28, and the duct 18 connecting the compartment 3 of the exchanger 1 to the waste liquid container 17 is not provided with a pump.
Moreover, a three-port valve 29 having the ducts 11, 13, and 14 connected thereto serves to connect the container 10 for the substitution/dialysis liquid either to the bubble trap 8 or to the compartment 3 of the exchanger 1, or else to isolate the container 10.
The operation of this second embodiment of the art i f i c i a l kidney of the invention is not significantly different from that of the preceding embodiment. In hemofiltration mode without infusion o f substitution liquid, the pump 12 is off and the flow rate of the pump 26 is controlled by the control unit 25 so that the filtration flow rate ~ measured by the scales 28 is equal to the sum of the reference weight loss flow rate QW~ and the infusion flow rate o f bicarbonate solution QHCO3 as measured by the scales 24.
In hemofiltration mode with infusion of substitution liquid, the pump 12 is on at a rate that is initially adjusted by the operator, and the rate of the pump 26 is controlled by the control unit 25 so that the filtration rate C~~ is equal to the sum of the reference weight loss rate Qw~, the infusion rate of bicarbonate solution QHC03~ and the infusion rate Q~N of substitution liquid as measured by the scales 27.
In dialysis mode, the pumps 6 and 26 on the blood c i rcu it respectively upstream and downstream from the exchanger 1 operate at the same rate, and the pump 12 which then serves as a pump f o r circulating the dialysis liquid operates at a rate that is set i n i t i a I I
y by the operator.
In hemodiafiltration mode, the control unit 25 controls the f I o w rate of the ~~pump 26 as in hemofiltration mode with infusion o f substitution liquid.
Except for hemofiltration mode in which the pump is off, the flow rate of the pump 12 for circulating the substitution/dialysis liquid is controlled by the control unit 25 which compares the desired flow rate stored initially in the memory of said unit with the flow rate as measured by the scales 27. The flow rate (spa of the pump 22 for infusing bicarbonate is controlled, as before, as a function o f the waste liquid flow rate r~ as measured by the scales 28, i n compliance with equation (1 ), or equation (2), as the case may be.
The invention is not limited to the embodiments described above and variants may be provided.
In particular, in contrast to the artificial kidney embodiments described above, in modes where the substitution/dialysis liquid i s circulated by the pump 12, it is possible to have the flow rate of the pump 19 (26) that controls the ultrafiltration flow rate as the rate that is fixed initially by the operator, with the flow rate of the pump 12 being controlled as a function of the difference between the fresh liquids and the waste liquids as infused and ultrafiltered, and the desired weight loss rate.
Moreover, the value of the liquid flow rates needed for controlling the pump 19 (26) controlling the ultrafiltration flow rate and for controlling the pump 22 for infusing the bicarbonate solution could be determined by measurement means other than scales, f o r example using flow rate meters or volume-measuring means.
Moreover, the pumps 12 and 22 used for controlling the f I ow rate of substitution/dialysis liquid and the flow rate of bicarbonate solution could be replaced by electromagnetically-operated clamps, with the liquids then flowing under gravity.
Also the source 10 of infusion liquid could be directly connected to the vascular system of the patient and not, as described before, to the circuit 5, 7 for extracorporeal blood circulation.
Finally, as mentioned above, the dosage means fitted to an artificial kidney of the invention may be used for dispensing all sorts of substances into the blood of a patient undergoing a treatment session by hemofiltration, hemodialysis, or hemodiafiltration. For a medicine A, for example, the container 20 would contain a sterile solution of the medicine with the container 10 containing a dialysis liquid in which the main electrolytes of blood are present, including bicarbonate. The operation of the kidney is not different from that described above with reference to the embodiments of Figures 1 and 2, and in particular, the infusion pump 22 is controlled as a function of the flow rate of waste liquid in application of equation (1 ) o r equation (2) as the case may be.
Claims (11)
1. A multifunction apparatus for circulating corporeal and medical liquids in an exchanger (1) having two compartments (2, 3) separated by a semipermeable membrane (4), a first compartment (2) being connected to an extracorporeal blood circuit (5, 7, 8) connectable to a patient (9), and a second compartment (3) having an inlet and an outlet, the apparatus comprising:
- first pumping means (12) for circulating a first sterile liquid;
- second pumping means (22) for circulating a second sterile liquid;
- third pumping means (6, 26) for circulating blood in the extracorporeal blood circuit (5, 7, 8);
- extraction means (19, 26) for causing ultrafiltration of a corporeal liquid through the membrane (4) of the exchanger (1);
- first weighing means (23 ; 27, 28) for weighing a first reservoir (10) for the first sterile. liquid, and a second reservoir (17) for a waste liquid, the first reservoir (10) being connectable to the inlet of the second compartment (3) of the exchanger, and the second reservoir (17) being connectable to the outlet of the second compartment (3) of the exchanger (1);
- second weighing means (24) for weighing a third reservoir (20) for the second sterile liquid, this reservoir being connectable t o the extracorporeal blood circuit (5, 7, 8); and - control means (25) for receiving at least weight information from the first weighing means (23 ; 27, 28) and the second weighing means (24) and for controlling at least one of the first, the second and the third pumping means (22, 12, 6, 26) and the extraction means (19, 26), from said at least weight information and from at least one information corresponding to a desired flow rate of at least one of the first sterile liquid, the second sterile liquid, the blood and the corporeal liquid.
- first pumping means (12) for circulating a first sterile liquid;
- second pumping means (22) for circulating a second sterile liquid;
- third pumping means (6, 26) for circulating blood in the extracorporeal blood circuit (5, 7, 8);
- extraction means (19, 26) for causing ultrafiltration of a corporeal liquid through the membrane (4) of the exchanger (1);
- first weighing means (23 ; 27, 28) for weighing a first reservoir (10) for the first sterile. liquid, and a second reservoir (17) for a waste liquid, the first reservoir (10) being connectable to the inlet of the second compartment (3) of the exchanger, and the second reservoir (17) being connectable to the outlet of the second compartment (3) of the exchanger (1);
- second weighing means (24) for weighing a third reservoir (20) for the second sterile liquid, this reservoir being connectable t o the extracorporeal blood circuit (5, 7, 8); and - control means (25) for receiving at least weight information from the first weighing means (23 ; 27, 28) and the second weighing means (24) and for controlling at least one of the first, the second and the third pumping means (22, 12, 6, 26) and the extraction means (19, 26), from said at least weight information and from at least one information corresponding to a desired flow rate of at least one of the first sterile liquid, the second sterile liquid, the blood and the corporeal liquid.
2. An apparatus according to claim 1, wherein the first weighing means includes two independent weighing means (27, 28) for weighing the first reservoir (10) and the second reservoir (17) respectively.
3. An apparatus according to claim 1, wherein the first weighing means comprises a single weighing means (23) for weighing both the first reservoir (10) and the second reservoir (17).
4. An apparatus according to one of the claims 1 to 3, wherein the extraction means comprises fourth pumping means (26) for circulating blood in the extracorporeal blood circuit (5, 7, 8), the third pumping means (6) and the fourth pumping means (26) being disposed upstream and downstream of the exchanger (1) respectively.
5. An apparatus according to one of the claims 1 to 3, wherein the extraction means comprises fourth pumping means (19) for circulating the waste liquid.
6. An apparatus according to one of the claims 1 to 5, comprising connecting means (15, 16 ; 29) for permitting the first reservoir (10) to be selectively connectable to the inlet of the second compartment (3) of the exchanger (1) or to the extracorporeal blood circuit (5, 7, 8).
7. An apparatus according to one of the claims 1 to 6, comprising dosage means (22,25) for adjusting a concentration of a substance (A), which is present in the second sterile liquid, to a desired concentration [A]DES in the blood of the patient (9), whereby a transfer of the substance (A) through the membrane (4) of the exchanger (1) is taken into account.
8. An apparatus according to claim 7, wherein the dosage means comprises means (22, 25) for adjusting a flow rate (QA) of the second sterile liquid as a function of a flow rate (QOUT) of the waste liquid.
9. An apparatus according to claim 8, wherein the flow rate (QA) of the second sterile liquid and the flow rate (QOUT) of the waste liquid are related by the equation:
where (A]SOL is a concentration of the substance (A) in the first sterile liquid.
where (A]SOL is a concentration of the substance (A) in the first sterile liquid.
10. An apparatus according to claim 7, wherein the dosage means comprises means (22, 25) for adjusting the flow rate (QA) of the second sterile liquid as a function of a clearance Cl of an artificial kidney for the substance (A).
11. An apparatus according to claim 10, wherein the flow rate (QA) of the second sterile liquid and the clearance Cl of the artificial kidney for the substance (A) are related by the equation:
where [A]SOL is a concentration of the substance (A) in the first sterile liquid.
where [A]SOL is a concentration of the substance (A) in the first sterile liquid.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR9111351 | 1991-09-10 | ||
| FR9111351A FR2680975B1 (en) | 1991-09-10 | 1991-09-10 | ARTIFICIAL KIDNEY WITH MEANS FOR DETERMINING A SUBSTANCE IN BLOOD. |
| CA002077848A CA2077848C (en) | 1991-09-10 | 1992-09-09 | Artificial kidney |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002077848A Division CA2077848C (en) | 1991-09-10 | 1992-09-09 | Artificial kidney |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2303714A1 CA2303714A1 (en) | 1993-03-11 |
| CA2303714C true CA2303714C (en) | 2003-07-08 |
Family
ID=25675506
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002303714A Expired - Lifetime CA2303714C (en) | 1991-09-10 | 1992-09-09 | Multifunctional apparatus for treatment of renal insufficiency |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2303714C (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ITMO20030259A1 (en) | 2003-09-25 | 2005-03-26 | Gambro Lundia Ab | USER INTERFACE FOR A TREATMENT MACHINE |
-
1992
- 1992-09-09 CA CA002303714A patent/CA2303714C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| CA2303714A1 (en) | 1993-03-11 |
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