Fresenius Medical Care North America Corporate Headquarters Medical Department To: FMCNA Medical Directors 95 Hayden Ave

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1 Fresenius Medical Care North America Corporate Headquarters Medical Department To: FMCNA Medical Directors 95 Hayden Ave Lexington, MA From: J. Michael Lazarus, M.D. Date: July 5, 2005 Re: Bicarbonate Levels Several years ago we initiated an effort to improve bicarbonate levels in patients in our dialysis facilities. At that time, I provided data indicating that the mean serum bicarbonate in the patient population was approximately 20 mmol/l with a number of patients below 18 mmol/l. A plan to educate staff and physicians was implemented regarding the manner by which the 2008H and 2008K machines deliver bicarbonate as well as our initiating use of GranuFlo (a dry bicarbonate delivery system). With these efforts, we have now increased the mean bicarbonate for FMCNA patients to approximately 24 mmol/l. I have enclosed a distribution graph of bicarbonate values for all patients (Figure 1) and a graph which shows the change in the mean bicarbonate ±1 standard deviation over the past several years (Figure 2). Figure 1

2 Page: 2 Figure 2 I have also enclosed a hazard risk analysis which identifies the risk of death at various levels of bicarbonate (unadjusted and with case mix and lab adjustment) (Figure 3). Figure 3

3 Page: 3 You will note from this death risk analysis that after adjustment for lab (nutrition), there is no statistically significant increase in death risk until patient bicarbonate pre-dialysis values are at or above 28 mmol/l and then the risk is only approximately 20%. This suggests that a level of pre-dialysis serum bicarbonate of up to 28 mmol/l would be acceptable. In recently published study by DOPPS, their study population was broken out in quartiles with the upper quartile (24 mmol/l and higher) demonstrating an increase risk of death. However, this broad quartile did not further break down the upper bicarbonate range. When analyzed further, as in our study, there is no increased hazard risk between 24 and 28 mmol/l of serum bicarbonate. However, I believe we are at a point where we should consider modulating the increase in bicarbonate values. Examination of the distribution curve of bicarbonate values for the entire Company as well as individual dialysis facilities demonstrates the persistence of biologic distribution i.e., some patients in each facility are at the acidotic end while others are at the alkalotic end of the curve. This suggests that bicarbonate therapy should be managed much like potassium that is, the vast majority of patients may be appropriately treated with a common bicarbonate dialysate prescription but some patients will require lower bicarbonate dialysate while others may require a higher bicarbonate dialysate. Such patients can be identified using the FMCNA Abnormal Report in Proton several examples of which I have enclosed (Attachments 1-3). Those of you who have not used these abnormal reports will find them useful in identifying those patients who may need a different bicarbonate prescription. Your Clinical Manager can run such reports for you. A final issue of which you should be aware is that GranuFlo derived dialysate delivers an additional 4 meq/l of sodium acetate (total of 8 meq/l). The acid in the acid concentrate is present to prevent precipitation of calcium when mixed with bicarbonate concentrate and to control the ph of the final dialysate. Acetic acid which is only available in liquid form is used in traditional liquid concentrates. GranuFlo was developed as a completely dry acid concentrate using Sodium Diacetate powder. Sodium Diacetate is a combination of Acetic Acid and Sodium Acetate; therefore the acetate concentration in GranuFlo is double that of traditional liquid acid concentrates. The acetate contributed from liquid acid concentrates or from GranuFlo to the final dialysate is metabolized by the patient, converting it to bicarbonate. Therefore, it is important to understand and prescribe a dialysate bicarbonate concentration which, in combination with the acetate in the acid concentrate, delivers the desired total buffer. We anticipate that for every 4 meq/l decrease or increase in the dialysate total buffer there will be a corresponding 1 2 meq/l change in the pre dialysis serum bicarbonate.

4 Page: 4 Examples: Bicarbonate Prescription Acetate Contribution Total Buffer 40 meq/l 4 meq/l (liquid acid) 44 meq/l 36 meq/l 8 meq/l (GranuFlo) 44 meq/l 38 meq/l 4 meq/l (liquid acid) 42 meq/l 34 meq/l 8 meq/l (GranuFlo) 42 meq/l 36 meq/l 4 meq/l (liquid acid) 40 meq/l 32 meq/l 8 meq/l (GranuFlo) 40 meq/l 34 meq/l 4 meq/l (liquid acid) 38 meq/l 30 meq/l 8 meq/l (GranuFlo) 38 meq/l I have enclosed four figures which represent face shots of the 2008 Delivery System. Note that one must add the acetate (left side and circled) to the bicarbonate content to obtain the total buffer. For example, in Example 1 (Liquid Concentrate), one would add 3.8 meq/l to 38 meq/l such that the total buffer delivered would be 41.8 meq/l. Example 1

5 Page: 5 In Example 2 (GranuFlo), one would add 7.6 meq/l to 38 which delivers 45.6 meq/l of buffer. Example 2 Also keep in mind that sodium modeling will change your delivered buffer. Example 3 shows the minimal potential buffer that could be delivered that is, a 20 meq/l bicarbonate dialysate with a 130 Na (e.g., with sodium modeling) with a liquid acetate (4.6 meq/l) would deliver 24.6 meq/l of buffer. Example 3

6 Page: 6 However, in Example 4, if you employ sodium modeling with a sodium of 155 with a GranuFlo dialysate, you could actually deliver a 48.7 meq/l buffer. Example 4 If you have questions or issues about bicarbonate/buffer delivery, please let us know. I believe this information about the current status of bicarbonate outcomes is important and may affect your dialysate prescription. JML/kr Enclosures

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