USE OF SODIUM NITROPRUSSIDE (SNP) FOR TREATMENT OF FULMINANT CONGESTIVE HEART FAILURE (CHF) IN DOGS WITH MITRAL REGURGITATION

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The purpose of this study was to retrospectively evaluate the management and outcome of 10 cases of severe fulminant mitral regurgitation (MR) treated with SNP at the Animal Emergency Center between June of 1997 and August of 2000. The presence of acute respiratory distress with echocardiograph findings consistent with mitral regurgitation; no response to oxygen, lasix, and nitroglycerine ointment after 2–4 hours; and radiographic evidence that over 75% of the lung fields were involved defined dogs with severe fulminant MR. SNP was started at a dose of 1 μg/kg/min. The dogs were monitored every 15 min by Doppler blood pressure, mucous membrane color, capillary refill time, respiratory rate, and auscultation of the lungs for respiratory crackles were recorded. If the blood pressure remained above 90 mmHg systolic and increased lung sounds were present, the dose of SNP was increased by 1 μg/kg/min every 15 min until respiratory crackles were reduced. These dogs were then maintained on that dose of SNP during what was called the ‘maintenance period’. During this maintenance period, they were evaluated for signs of respiratory distress and blood pressure monitoring was recorded every 2 hours. The dogs were started on an angiotensin‐converting enzyme inhibitor during the maintenance period, and slowly tapered off the SNP. If the blood pressure decreased below 90 mmHg systolic, the dose of SNP was reduced to the previous dose. Eight dogs survived to discharge, one dog died 1 hour after starting SNP, and one dog was euthanized after 2 hours of SNP treatment. In the 8 dogs that survived, respiratory distress improved within 2 hours in 7 dogs (mean: 1.69, median: 2, range: 1.15–2) at a SNP dose of 1–3 μg/kg/hr (mean: 1.75, median: 1.5 and range: 1–3). Respiratory distress improved in one dog within 6 hours on SNP at a dose of 5 μg/kg/hr. In the survival group, SNP was maintained for 9–20 hours (mean: 14, median: 13 and range: 9–22). The taper of SNP occurred over 2–3 hours (mean: 4.2, median: 3 and range: 0–14) in 7 of the dogs that survived. One dog was tapered over 14 hours due to periodic episodes of hypotension and respiratory distress. The results suggest that use of SNP for treatment of dogs with CHF secondary to MR resulted in improvement in respiratory distress in 8 of the 10 dogs evaluated, and may be an effective alternative therapy for dogs with severe refractory CHF due to MR.

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