[Bicarbonate: From physiology to treatment for all clinicians]

Acid-base regulation is essential to maintain homeostasis in humans. Carbonic acid/bicarbonate (H₂CO₃/HCO₃^-) couple is the most predominant extracellular buffer to keep plasma pH within a physiological range. The ability to (re)generate such a buffer is a key milestone that necessitates to understand a precise physiology of both renal tubule and digestive tract. Here, we first reviewed renal and digestive cycles of bicarbonate in physiology. We also reviewed pathological findings where acid-base disequilibrium is involved and nutritional and/or alkali therapy could be necessary. Secondly, data from clinical trials were synthesized. Alkali therapy, oral and parenteral, from mineral-based water, masterful preparations or pharmaceutics drugs, is regularly used in a wide range of clinical findings, even if supporting data are (often) of a low level of evidence. Bicarbonate is primarily used during contrast-induced nephropathy, metabolic acidosis in chronic kidney disease or nephrolithiasis in which alkaline urine is necessary. Cast nephropathy, rhabdomyolysis and tumor lysis syndrome make usually physicians prescribe alkali therapy even if this prescription is only supported by physiopathological data without any proven clinical results. Finally, bicarbonate is essential in the composition of dialysate in both hemodialysis and peritoneal dialysis.