Metabolic complications in chronic kidney disease: hyperphosphatemia, hyperkalemia and anemia

Metabolic complications of chronic kidney disease (CKD) are frequent; the aims of this review are to present a 2018 update for hyperkalemia, hyperphosphatemia and anemia. Hyperkalemia is defined by a plasma level above 5.0 mmol/L, after ruling out pre-analytical problems such as hemolysis. It is frequent in CKD, most often due to drugs and notably renin/angiotensin blockers. Chronic hyperkalemia is deleterious, with an increased risk of mortality. Therapeutic strategies to decrease the incidence and severity of hyperkalemia are therefore crucial in nephrology: experts recommend to maintain the renin/angiotensin blockers as long as possible, whilst associating diuretics and potassium binders. There are apparent discrepancies between optimal protein intake and decreased phosphate intake in CKD; this is even more important in dialysis since protein decrease is associated with denutrition and subsequent increased risk of mortality. Nutritional phosphate intake from vegetables are less absorbed; in contrast, phosphate additives are almost completely absorbed in the gastro-intestinal tract. These "hidden" intake may increase the total daily phosphate intake by 1 000 mg. As such in addition to optimized dialysis, phosphate binders should be used but compliance may be challenging on the long-term. Educational programs focused on phosphate are also mandatory in CKD patients. "Absolute" iron deficiency is less frequent than "functional" iron deficiency in CKD patients: both require the use of iron supplementation, and the latter may benefit from additional erythropoietin stimulating agents (ESA) when hemoglobin is below 10 g/dL. Intravenous iron is more efficient to correct iron deficiency both in pre-dialysis and dialysis especially in patients with chronic deficiency. Last generation intravenous preparations have largely demonstrated their safety. One indication of iron supplementation one should not forget in nephrology is the patient with moderate CKD and heart failure since the expected benefits are multiple, notably in terms of quality of life, renal function and functional capacity. (C) 2018. Societe francophone de nephrologie, dialyse et transplantation. Published by Elsevier Masson SAS. All rights reserved.