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

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 ]) × m[Cl ].

RESULTS

Corrected [Cl ] and m[Cl ] were lower in Stage D vs Stage C and NO-CHF (all P < .0001). The c[Cl ] was higher than m[Cl ] in Stage D (P < .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 = .0003). No hypochloremic Stage D dogs had normal c[Cl ], but 11/24 had [Cl ] that was increased by >2 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.