Removal of carbon dioxide via dialysis

• US 10,322,221 B2
• Filed: 01/18/2014
• Issued: 06/18/2019
• Est. Priority Date: 01/18/2013
• Status: Active Grant

• Current Assignee: University of Pittsburgh of The Commonwealth System of Higher Education
• Original Assignee: University of Pittsburgh of The Commonwealth System of Higher Education
• Inventors: Kellum, Jr., John Alston, Cove, Matthew, Federspiel, William J.
• Primary Examiner(s): Fortuna, Ana M
• Application Number:
  US14/761,321
• Publication Number:
  US 20150335807A1
• Time in Patent Office: 1,977 Days
• CPC Class Codes: A61M 1/1613 Profiling or modelling of patient or predicted treatment evolution or outcome
• CPC Class Codes: A61M 1/1654 Dialysates therefor
• CPC Class Codes: A61M 1/1694 with recirculating dialysing liquid
• CPC Class Codes: A61M 1/1698 Blood oxygenators with or without heat-exchangers intracorporal A61M1/1678; manufacturing of membranes therefor B01D67/00; semi-permeable membranes for separation processes characterised by their properties B01D69/00; semi-permeable membranes characterised by their material B01D71/00
• CPC Class Codes: A61M 2230/202 partial carbon oxide pressure, e.g. partial dioxide pressure (P-CO2)
• CPC Class Codes: A61M 2230/208 pH-value
• CPC Class Codes: B01D 2311/13 Use of sweep gas
• CPC Class Codes: B01D 61/244 comprising multiple dialysis steps
• CPC Class Codes: B01D 63/02 Hollow fibre modules

Abstract

A method of reducing the concentration of carbon dioxide in blood plasma includes removing blood from a patient and treating or processing at least blood plasma of the blood by flowing the blood plasma on one side of at least one semi-permeable membrane and flowing a dialysate on the other side of the at least one semi-permeable membrane. The dialysate has a concentration of bicarbonate less than the concentration of bicarbonate in the blood plasma before treating the blood plasma and has a composition such that the blood plasma strong ion difference that results from treating the blood plasma in conjunction with an achieved reduction in blood plasma CO2 concentration results in a blood plasma pH that does not change by more than +/−0.5 during treatment.

Claims

1. A method of reducing the partial pressure of carbon dioxide or pCO₂ in blood or blood plasma during renal replacement therapy comprising:

removing blood from a patient;

treating the blood or blood plasma which has been separated from the blood by flowing the blood or the blood plasma on one side of at least one semi-permeable membrane, wherein carbonic anhydrase is immobilized on or in the vicinity of the at least one semi-permeable membrane, and flowing a dialysate for renal replacement therapy on the other side of the at least one semi-permeable membrane to reduce the concentration of bicarbonate in the blood or the blood plasma and reduce pCO₂ in the blood or the blood plasma, the dialysate having a concentration of bicarbonate less than the concentration of bicarbonate in the blood or the blood plasma before treating the blood or the blood plasma and having a composition such that the blood or the blood plasma strong ion difference that results from treating the blood or the blood plasma in conjunction with an achieved reduction in pCO₂ results in a blood pH or a blood plasma pH at an interface of the at least one semi-permeable membrane between 6.5 and 8.5 during treatment such that pCO₂ in the blood or blood plasma is reduced without inducing metabolic acidosis; and

returning the blood or the blood plasma to the patient after treating the blood or the blood plasma on one side of the at least one semi-permeable membrane.

2. The method of claim 1 further comprising reducing the concentration of bicarbonate in the dialysate after the dialysate contacts at least one semi-permeable membrane and recycling the dialysate after reducing the concentration of bicarbonate.

3. The method of claim 1 further comprising increasing the pH of the blood or the blood plasma before the blood or the blood plasma flows on one side of the at least one semi-permeable membrane.

4. The method of claim 1 wherein the concentration of bicarbonate in the dialysate is no more than half the concentration of bicarbonate in the blood or the blood plasma before treating the blood or the blood plasma.

5. The method of claim 1 wherein the concentration of bicarbonate in the dialysate is in the range of 5 mmol and 0 mmol.

6. The method of claim 1 wherein the composition of the dialysate is determined on a per-patient basis.

7. The method of claim 6 wherein the composition of the dialysate is determined on the basis of at least one of a level of hypercarbia, a level of respiratory acidosis and a level of metabolic acidosis.

8. The method of claim 1 wherein the composition of the dialysate is determined on the basis of at least one of a patient baseline blood or blood plasma CO₂ concentration, a desired blood or blood plasma CO₂ concentration, blood or blood plasma strong ion difference and blood or blood plasma weak acid concentration.

9. The method of claim 1 further comprising determining a desired outcome level of pCO₂, using the following equation to determine blood or blood plasma strong ion difference or SID for the desired outcome level of pCO₂:

10. The method of claim 9 further comprising using the following equation to determine pH at the interface of the at least one semi-permeable membrane using the following equation:

SID={K_c*pCO₂/[H⁺]−

2*K_cK₃*pCO₂/[H⁺]²−

K_w/[H⁺]K_a*[A_tot]/(K_a+[H⁺])−

[H⁺]}*(1−

σ

)

for mixing of equal amounts of the dialysate and the blood or the blood plasma, wherein (1−

σ

) is a sieving coefficient.

11. The method of claim 10 further comprising adding a buffer which does not increase bicarbonate concentration in the blood to the dialysate if the pH at the interface of the at least one semi-permeable membrane and the blood or the blood plasma is outside of a desired range.

12. The method of claim 1 wherein the blood is caused to flow on the one side of the at least one semi-permeable membrane and the blood is returned to the patient.

13. A system for reducing the partial pressure of carbon dioxide or pCO₂ in blood or blood plasma during renal replacement therapy comprising:

a dialysis filter system comprising at least one semi-permeable membrane, wherein carbonic anhydrase is immobilized on or in the vicinity of the at least one semi-permeable membrane; and

a source of a dialysate for renal replacement therapy having a concentration of bicarbonate less than the concentration of bicarbonate in the blood or blood plasma before treating the blood or the blood plasma and having a composition such that the blood or the blood plasma strong ion difference that results from treating the blood or the blood plasma in conjunction with an achieved reduction in blood or blood plasma pCO₂ results in a blood or a blood plasma pH at an interface of the at least one semi-permeable membrane between 6.5 and 8.5 during treatment such that pCO₂ in the blood or blood plasma is reduced without inducing metabolic acidosis.

14. The system of claim 13 further comprising a recycling system to reduce the concentration of bicarbonate in the dialysate after the dialysate contacts the at least one semi-permeable membrane and return the dialysate with the reduce concentration of bicarbonate to the source of dialysate.

15. The system of claim 13 further comprising a system to increase the pH of the blood or the blood plasma before the blood or the blood plasma flows on one side of the at least one semi-permeable membrane and a system to decrease the pH of the blood or the blood plasma after the blood or the blood plasma flows on one side of the at least one semi-permeable membrane.

16. The system of claim 13 wherein the concentration of bicarbonate in the dialysate is in the range of 5 mmol and 0 mmol.