Author + information
- Hoong Sern Lim, MD∗ ()
- ↵∗University Hospital Birmingham, NHS Foundation Trust, Edgbaston, Birmingham B15 2TH, United Kingdom
Grodin et al. (1) showed that low admission chloride levels are associated with worse outcomes in patients with acute decompensated heart failure (ADHF). The prognostic value of chloride level may reflect greater congestion (dilution), diuresis (depletion), or acid-base disturbance (buffer) and deserves discussion in the context of the data presented by the authors.
Free water excess often produces hyponatremia in ADHF (2) and would similarly result in dilutional hypochloremia. A greater absolute reduction in sodium compared with chloride level would be expected at a particular degree of dilution given the higher sodium compared with chloride levels in the extracellular fluid. The data presented paradoxically showed a greater reduction in chloride compared with sodium, assuming normal sodium and chloride levels of 140 mEq/l and 106 mEq/l (3), suggesting that the degree of hypochloremia is unlikely to be dilution alone. It is also unlikely that dilutional hypochloremia would be prognostically more significant than dilutional hyponatremia.
Loop diuretics inhibit the sodium-potassium-chloride cotransporter (stoichiometric balance of 1:1:2) and will produce a proportionately greater reduction in chloride than sodium. In addition, chloride is readily altered to regulate plasma strong ion difference (SID) and maintain the acid-base balance. Chloride and sodium are the major strong anion and cation in extracellular fluid and key determinants of SID. The electrochemical effects of SID affect water dissociation and hence hydrogen ([H+]) concentration. As SID becomes more positive, [H+], a “weak” cation decreases to maintain electrical neutrality. A reduction in SID from a net increase in anions has the opposite effect, resulting in acidosis. Hence, the larger reduction in chloride relative to sodium may reflect greater loop diuretic use and/or the presence of unmeasured anions, both of which may explain the prognostic value of chloride levels. Additional data on diuretic therapy and measures of acid-base balance will shed light on these possible mechanisms.
Please note: Dr. Lim has reported that he has no relationships relevant to the contents of this paper to disclose.
- 2015 American College of Cardiology Foundation
- Grodin J.L.,
- Simon J.,
- Hachamovitch R.,
- et al.
- Verbrugge F.H.,
- Steels P.,
- Grieten L.,
- Nijst P.,
- Tag W.H.W.,
- Mullens W.