Abnormal Serum Bicarbonate Concentration in Hemodialysis Patients

Abstract

I read with great interest the article by Drs Lisawat and Gennari,1Lisawat P. Gennari F.J. Approach to the hemodialysis patient with an abnormal serum bicarbonate concentration.Am J Kidney Dis. 2014; 64: 151-155Abstract Full Text Full Text PDF PubMed Scopus (16) Google Scholar which presents a patient with a high predialysis serum bicarbonate concentration due to low endogenous acid production. According to the authors (and described in Box 1 of their article1Lisawat P. Gennari F.J. Approach to the hemodialysis patient with an abnormal serum bicarbonate concentration.Am J Kidney Dis. 2014; 64: 151-155Abstract Full Text Full Text PDF PubMed Scopus (16) Google Scholar), excessive alkali administration in a patient receiving hemodialysis is a cause of elevated predialysis serum bicarbonate level. They also emphasize that there is no evidence that reducing dialysate bicarbonate concentration lessens morbidity and mortality. However, there is no reason to give bicarbonate to patients without metabolic acidosis or with metabolic acidosis overcorrected by previous dialysis bicarbonate overload (the latter could be iatrogenic metabolic alkalosis). Hence I disagree with the authors’ decision to treat a patient’s high predialysis serum bicarbonate concentration by using a dialysate with such a high concentration of alkali (bicarbonate plus citrate) because in my opinion, even little net bicarbonate gain is inappropriate. Regarding the mystery of a lower postdialysis serum bicarbonate level than expected, I suppose that enhanced ventilatory excretion of carbon dioxide throughout the dialysis session, despite the presence of alkalosis,2Symreng T. Flanigan M.J. Lim V.S. Ventilatory and metabolic changes during high efficiency hemodialysis.Kidney Int. 1992; 41: 1064-1069Crossref PubMed Scopus (47) Google Scholar could clear away some bicarbonate in the form of carbon dioxide. Financial Disclosure: The author declares that he has no relevant financial interests. Approach to the Hemodialysis Patient With an Abnormal Serum Bicarbonate ConcentrationAmerican Journal of Kidney DiseasesVol. 64Issue 1PreviewWe present a patient receiving hemodialysis with a persistently high serum bicarbonate concentration to illustrate the evaluation and management issues for patients with both high (>25 mEq/L) and low (<20 mEq/L) pretreatment values. Patients with high serum bicarbonate concentrations typically are malnourished and have low rates of endogenous acid production. Evaluation should begin with assessment of whether an acute and potentially reversible cause of metabolic alkalosis is present. If not, management should be directed at treating malnutrition. Full-Text PDF In Reply to ‘Abnormal Serum Bicarbonate Concentration in Hemodialysis Patients’ and ‘A “Lingering Mystery” of Postdialysis Serum Bicarbonate Concentration’American Journal of Kidney DiseasesVol. 64Issue 6PreviewDr Marano1 argues that we have sustained our patient’s metabolic alkalosis by not reducing dialysate bicarbonate concentration and that it therefore is iatrogenic in origin. I disagree. The cause of the patient’s high serum bicarbonate level is low endogenous acid production, with which Dr Havlin2 agrees. However, Dr Havlin2 states that we should eliminate unnecessary alkalinization by reducing dialysate bicarbonate concentration. There is no evidence that reducing dialysate bicarbonate concentration is helpful in this setting; the increase in mortality is due to factors unrelated to acid-base status. Full-Text PDF