Correction of serum chloride concentration in dogs with congestive heart failure.

Abstract

BACKGROUND: Hypochloremia associated with congestive heart failure (CHF) in dogs is likely multifactorial. Loop diuretics cause 1:2 sodium [Na]:chloride [Cl] loss, whereas water retention causes a 1:1 [Na]:[Cl] dilution. Mathematical [Cl] correction separates these effects on [Cl]. HYPOTHESIS: We hypothesized that corrected [Cl] (c[Cl]) would not differ from measured [Cl] (m[Cl]) in dogs with controlled CHF because of loop diuretics, and dogs with refractory CHF would have higher c[Cl] than m[Cl], indicating relative water excess. ANIMALS: Seventy-one client-owned dogs with acquired heart disease, without CHF (NO-CHF), 76 with Stage C CHF and 24 with Stage D CHF. METHODS: Clinicopathological data from a previous study were retrospectively analyzed. Corrected [Cl], m[Cl], and differences were compared among NO-CHF, Stage C CHF, and Stage D CHF, using the formula: c[Cl] = (mid-reference range [Na]/measured [Na]) &#xd7; m[Cl]. RESULTS: Corrected [Cl] and m[Cl] were lower in Stage D vs Stage C and NO-CHF (all P <&#x2009;.0001). The c[Cl] was higher than m[Cl] in Stage D (P <&#x2009;.0001) but not Stage C or NO-CHF. Median difference between c[Cl] and m[Cl] was higher for Stage D vs Stage C (P =&#x2009;.0003). No hypochloremic Stage D dogs had normal c[Cl], but 11/24 had [Cl] that was increased by >2&#x2009;mmol/L. CONCLUSIONS AND CLINICAL IMPORTANCE: Serum [Cl] increased after mathematical correction in Stage D CHF dogs but not in Stage C and NO-CHF dogs. Although c[Cl] was higher than m[Cl] in Stage D dogs supportive of relative water excess, hypochloremia persisted, consistent with concurrent loop diuretic effects on electrolytes. Future study correlating c[Cl] to antidiuretic hormone concentrations is warranted.