Measuring Sodium in dialysis patients. UCL Center for Nephrology

Transcription

1 Measuring Sodium in dialysis patients UCL Center for Nephrology

2 sodium Na-heparin sulphate Na-dermatan sulphate Na-chondroitin sulphate endothelium Na-heparin sulphate Na-Sulfate plasma protein Na-Citrate Na-organic acid Na-Chloride Na-Bicarbonate RBC Na-Phosphate Albumin

3 Sodium binding chemical electrical

4 Sodium concentration vs activity concentration total amount activity Exchangeable sodium

5 sodium Measurement Indirect potentiometer main laboratory analyzer Direct potentiometer blood gas analyzer Flame photometer Ion electrophoresis Absorption spectroscopy

6 sodium Measurement Indirect potentiometer dilutes serum sample measures electrical charge compares with standard curve Standards protein content lipid content normal blood glucose reports activity Estimates sodium concentration assumption normal protein/lipid/glucose

7 sodium Measurement Direct potentiometer plasma sample measures electrical charge compares with standard curve Standards protein content lipid content normal blood glucose reports activity Estimates sodium concentration assumption normal protein/lipid/glucose

8 Sodium in fluids Biological fluids Plasma Proteins Lipids Organic/non-organic acids Serum no clotting proteins Qu does plasma sodium differ from serum sodium?

9 How reliable is your laboratory?

10 Sodium in fluids Dialysis fluids Hemodialysis dialysate No Proteins No Lipids No organic acids contains bicarbonate chloride acetate/citrate glucose

11 Sodium in fluids Dialysis fluids Hemodialysis dialysate No Proteins No Lipids No organic acids contains bicarbonate chloride acetate/citrate glucose Peritoneal dialysate No Proteins No Lipids No organic acids contains lactate/bicarbonate chloride acetate/citrate Glucose iso-maltose amino acids GDPs

12 Sodium in fluids Dialysis fluids Hemodialysis dialysate No Proteins No Lipids No organic acids contains bicarbonate chloride acetate/citrate glucose Peritoneal dialysate No Proteins No Lipids No organic acids contains lactate/bicarbonate chloride acetate/citrate Glucose iso-maltose amino acids GDPs Qu does haemodialysis sodium differ from peritoneal dialysate sodium?

13 Sodium in fluids Can we simply use dialysate samples? indirect potentiometer direct potentiometer proteins lipids organic/non-organic acids viscosity need different standards

14 Indirect potentiometer interference glucose lipids paraproteins icodextrin

15 Hemodialysis dialysate composition acid RO water bicarbonate conductivity

16 conductivity Measurement of electrical charge sodium chloride bicarbonate acetate citrate potassium calcium magnesium Temperature

17 conductivity Check conductivity dialysis machine manufacturer single close range wider range acetate

18 conductivity Check conductivity dialysis machine manufacturer single close range wider range acetate

19 Hemodialysis dialysate composition acid RO water bicarbonate ph conductivity

20 Increase dialysate sodium? acid RO water bicarbonate ph conductivity

21 Increase dialysate sodium? acid RO water bicarbonate ph conductivity

22 hemodialysis acid RO water bicarbonate ph conductivity

23 conductivity

24 You sure the dialysate sodium was 138? Reality check Difference Plot Identity 15 Bias (-0.7) 10 95% Limits of agreement (-10.8 to 9.4) 5 Difference (NaF - NaD) Mean 135 of All

25 Dialysate errors acid concentrate dialysis water bicarbonate A fluid Na+ = 102 BiBag Na+ = 35 conductivity cell

26 Dialysate errors acid concentrate dialysis water bicarbonate A fluid Na+ = 102 BiBag Na+ = 35 The Base Na therefore = ( ) = 137mmol/l The Assumption: To reach a prescribed Na of 140mmol/l the dialysis machine will marginally increase the volume of A fluid in the mixture.

27 conductivity

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29 How do we get a 140 sodium? BiBag Na+ = 35 The Base Na therefore = ( ) = 137mmol/l A fluid Na+ = 102 The Assumption: To reach a prescribed Na of 140mmol/l the dialysis machine will marginally increase the volume of A fluid in the mixture.

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33 The BiBag contains Sodium Bicarbonate (NaHCO3) powder and the default machine setting was 35 mmol/l of sodium bicarbonate solution HOWEVER! The 3 mmol of acetic acid in the A fluid react with 3 mmol of NaHCO3 from the BiBag solution via the equation 3(CH3COOH) + 3(NaHCO3) >> 3(NaCH3COO) + 3(H2O) + 3(CO2) Therefore to achieve a final dialysis fluid bicarbonate level of 35mmol/l, it is necessary to produce 38mmol/l of sodium bicarbonate solution.

34 How many mmol/l of NaCl are there? A/985: 268.2g of NaCl RMM of NaCl = ( ) = x 1000 = mmol/l in acid concentrate 58.3 This is diluted in a 1:44 ratio (or 1 in 45) So the final concentration in our diluted A solution is = mmol/l 45

35 How many mmol/l of NaCl are there? A17: 263g of NaCl RMM of NaCl = ( ) = x 1000 = 4496 mmol/l in acid concentrate 58.5 This is diluted in a 1:44 ratio (or 1 in 45) So the final concentration in our diluted A solution is 4496 = 100 mmol/l 45

36 Label for A17

37 New Kimal concentrate

38 Dialysate composition 1:44 dilution A/ A/ A330 Acid concentrate Purified water 8.4% NaHCO 3

39 Dialysate errors

40 Sodium Serum sodium o Indirect potentiometer o Direct potentiometer o glucose o Dialysate sodium o Conductivity o Flame photometry

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