Correction of Dialysis-Induced Metabolic Alkalosis

Huber and Gennari demonstrated success in reducing severe alkalosis in patients with ESRD due to vomiting with the use of HCO₃ bath of 30 mEq/L.¹⁴ In their report, the calculated bicarbonate dropped from 94 to 39 mEq/L; after 3 hours of HD, their patient also was receiving 2 L of an isotonic saline infusion daily. These observations suggest that lowering bicarbonate in the bath is effective in much more severe cases than ours, and even then, extra measures are needed to bring it down to desirable levels. In the early days, some health care providers used a specially prepared high-chloride (123 mEq/L) and low-acetate dialysate (18 mEq/L), which increased serum chloride and hydrogen ion concentrations and decreased the serum bicarbonate concentration compared with those in commercially available high-acetate dialysate (containing 37 mEq/L acetate and 104 mEq/L Cl).¹⁵ However, this method requires special preparation of dialysate. Oral potassium chloride also was used to correct metabolic alkalosis, but the risk of potassium overload precludes this approach in patients with ESRD.¹⁶

Likewise, adding oral sodium chloride risks causing volume overload, especially in patients with cardiomyopathy; it may increase thirst, resulting in interdialytic excess volume gains.¹⁷ In our patient, respiratory compensation took place by correcting pulmonary congestion by UF, and the gentle bicarbonate removal in addition to boosting chloride levels promptly improved the metabolic alkalosis.

Notably adequate volume control achieved by HD in persons with small muscle mass and severe cardiomyopathy can require longer treatment duration than required to achieve adequate clearance. Accordingly, more bicarbonate loading can take place, causing metabolic alkalosis. This problem is compounded by the potential overdelivery of bicarbonate than that entered by the physician’s order.¹

Conclusions

Attention should be paid to detect elevated predialysis serum bicarbonate levels in ESRD patients on HD, especially those with values above 27 mmol/L due to higher mortality.^6,7 Treatment of these patients is more challenging than for those who are acidotic predialysis, especially when alkalosis is compounded by malnutrition. Mitigation of this problem is achieved by using a lower bicarbonate bath and the shortest effective dialysis duration that achieves adequate clearance. Poor clearance also deleteriously affects patient nutrition and well-being. We have shown that normal saline solution infusion with concurrent removal by UF can correct pretreatment metabolic alkalosis when other measures are inadequate.