Canine congestive heart failure (CHF) is staged using the ACVIM classification system, and stage C (symptomatic) disease is treated with quadruple therapy: furosemide or torsemide, pimobendan, spironolactone, and enalapril or benazepril. MSD Vet Manuals
Staging drives treatment decisions. Stage B1 describes preclinical disease without cardiac remodeling, and stage B2 describes preclinical disease with echocardiographic evidence of remodeling — both are asymptomatic. Stage C is symptomatic CHF responsive to standard therapy, and stage D is refractory CHF despite standard therapy. Journal of Vete… Dogs with stage D disease are distinguished in part by serum chloride below 103.5 mmol/L, which accurately identifies this refractory population. Journal of Vete…
For acute decompensated CHF, furosemide is administered at 2 mg/kg IV at presentation, followed by oral furosemide at 2.3 mg/kg PO q12h [4.6 mg/kg/day total] for ongoing management. Journal of the… When furosemide becomes insufficient at higher doses in refractory (stage D) disease, earlier transition to torsemide is warranted, as furosemide oral bioavailability does not correlate reliably with serum concentration at higher doses. Journal of Vete…
Chronic stage C management combines four drug classes. Spironolactone is initiated at 1.5 mg/kg PO q12h [3 mg/kg/day total], and enalapril at 0.4 mg/kg PO q12h [0.8 mg/kg/day total]. Journal of the… Pimobendan is included as the inodilator component of quadruple therapy. MSD Vet Manuals Inhibition of the renin-angiotensin-aldosterone system (RAAS) with ACE inhibitors and spironolactone improves potassium retention and increases beneficial RAAS metabolites in stage C and D dogs. Journal of Vete…
Dietary sodium restriction is recommended alongside pharmacologic therapy. A low-sodium diet with balanced protein, phosphorus, and antioxidants is appropriate for stage C dogs. Journal of the… High-sodium food and treats should be avoided. Journal of the…
Fluid therapy is approached with caution in CHF patients. When IV fluids are necessary, 0.45% NaCl with 2.5% dextrose administered at half to daily maintenance rates is the recommended formulation. AAHA Clinical G… Hypotension in CHF should be addressed with positive inotropes rather than fluid boluses. AAHA Clinical G…
Monitoring after initiating therapy includes a renal panel in 1–2 weeks and echocardiography at 3 months. Ongoing clinical surveillance targets persistent cough, tachypnea, dyspnea, exercise intolerance, and syncope. Journal of the… Serum chloride should be tracked in dogs on loop diuretics, as hypochloremia is exacerbated by loop diuretic inhibition of the Na/K/2Cl cotransporter and signals progression toward stage D. Journal of Vete…
| Drug | Dose & Route | Role | Key Caveat |
|---|---|---|---|
| Furosemide | 2 mg/kg IV (acute); 2.3 mg/kg PO q12h (chronic) | Loop diuretic | Transition to torsemide in stage D when high-dose furosemide fails Journal of Vete… |
| Pimobendan | Per quadruple therapy protocol | Inodilator | Component of standard stage C quadruple therapy MSD Vet Manuals |
| Spironolactone | 1.5 mg/kg PO q12h | Aldosterone antagonist / RAAS modulator | Improves potassium retention in stage C–D Journal of Vete… |
| Enalapril | 0.4 mg/kg PO q12h | ACE inhibitor | Renal panel recheck in 1–2 weeks after initiation Journal of the… |
Would you like guidance on when and how to transition from furosemide to torsemide in a dog progressing toward stage D?