Dobutamine
Dobutamine is a synthetic beta-adrenergic agonist that is sometimes useful in improving inotropic activity of the myocardium
in severe cases of CHF, especially in patients with dilated cardiomyopathy. At lower dosages, dobutamine improves cardiac
contractility with minimal effects on heart rate. This improves contractile function with minimal effects on myocardial oxygen
demand. At higher dosages, however, dobutamine can be proarrhythmogenic, so carefully monitor the patient's ECG during the
constant-rate infusion. To administer dobutamine (2 to 20 μg/kg/min), start with a low dose and gradually increase the dose
until the desired effect is achieved. Potential side effects include tachyarrhythmias (at higher doses), facial twitching,
and seizures.25,26 Cats are more at risk for complications associated with dobutamine infusion.
PERICARDIOCENTESIS
If pericardial effusion is diagnosed, pericardiocentesis can be a temporary lifesaving procedure until fluid reaccumulates
or more definitive palliative therapy is performed. Before attempting pericardiocentesis, perform a prothrombin time to rule
out pericardial hemorrhage secondary to vitamin K antagonist rodenticide intoxication.
To perform pericardiocentesis, place the patient in left lateral recumbency, and shave a 10-cm square caudal to the point
of the elbow on the right lateral body wall. Aseptically scrub the clipped area, and, ideally, drape the area with sterile
field towels. While wearing sterile gloves, infuse 1 mg/kg 2% lidocaine through the skin and intercostal muscles between the
fifth and sixth intercostal space dorsal to the sternum to create an anesthetized subcutaneous tunnel through which the catheter
can be inserted.
Monitor the patient's ECG throughout the procedure for potential life-threatening cardiac dysrhythmias. Make a small nick
incision through the skin with a No. 11 scalpel blade, and insert a 16-ga, 5.5 in catheter (Abbocath-T—Abbott Laboratories)
through the skin and intercostal muscles into the pleural space and pericardial sac.
A flash of blood will appear in the hub of the catheter as the catheter and stylet penetrate the pericardial sac. At this
point, push the catheter off the stylet, and attach the hub of the catheter to a length of intravenous extension tubing, three-way
stop-cock, and 60-ml syringe to remove the pericardial effusion. Place a small amount of the effusion into a red-topped tube,
and monitor it for clots. Clots can form because of acute hemorrhage or iatrogenic puncture into the ventricular lumen. Removing
even small amounts of pericardial fluid can drastically improve ventricular preload and cardiac output.
CONCLUSION
Irrespective of the underlying cause of CHF, affected patients must be treated carefully and aggressively after initial diagnosis.
Supplemental oxygen, potent diuretics, and nitric oxide donors continue to be the mainstay of therapy in both cats and dogs
during the initial treatment of CHF. Patients that do not respond to standard therapies may require additional therapies,
including positive inotropic and intravenous vasodilatory drugs. Carefully monitor heart rate and rhythm, arterial blood pressure,
respiratory rate and effort, and pulse oximetry or arterial oxygen saturation to evaluate a patient's response to therapy.
Elisa M. Mazzaferro, MS, DVM, PhD, DACVECC
Wheat Ridge Veterinary Specialists
3695 Kipling St.
Wheat Ridge, CO 80033.
Dr. Mazzaferro lectured on this topic at the 2005 Central Veterinary Conference. Her paper originally appeared in the conference
proceedings.
REFERENCES
1. Sisson DD, Ettinger SJ. The physical exam. In: Fox PR, Sisson D, Moise NS, eds. Textbook of canine and feline cardiology. Philadelphia, Pa: WB Saunders Co., 1999.
2. Wall RE, Rush JE. Cardiac emergencies. In: Murtaugh RJ, Kaplan PM, eds. Veterinary emergency and critical care. St. Louis, Mo: Mosby-Year Book, 1992.
3. Butson R. Treatment of congestive heart failure. J Small Anim Pract 2003;44:516.
4. Beardow AW. The diagnostic and therapeutic approach to the patient in acute congestive heart failure. Clin Tech Small Anim Pract 2000;15:70-75.
5. Kittleson MD. Pathophysiology and treatment of heart failure. In: Tilley LP, Owens JM, eds. Manual of small animal cardiology. New York, NY: Churchill Livingstone, 1985;307-332.
6. Root CR, Bahr RJ. The heart and great vessels. In: Thrall DR, ed. Textbook of veterinary diagnostic radiology. Philadelphia, Pa: WB Saunders Co., 1994.
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