Pharmacological Characteristics #
Dopamine is an endogenous catecholamine with dose-dependent receptor affinity and effects. At low doses (1-5 μg/kg/min), it primarily activates dopaminergic receptors, at intermediate doses (5-10 μg/kg/min) it activates beta-1 adrenergic receptors, and at high doses (>10 μg/kg/min) alpha-1 effects predominate (Plumb, 2018). Dobutamine is a synthetic catecholamine with predominant beta-1 adrenergic activity and minimal beta-2 and alpha effects, designed specifically for cardiac support (Silverstein & Hopper, 2015).
Hemodynamic Effects #
Dopamine increases heart rate and contractility through beta-1 stimulation, with dose-dependent effects on preload and afterload. At higher doses, it increases afterload through alpha-mediated vasoconstriction (Pascoe, 2014). This effect may be especially helpful during inhalant-anesthetic associated hypotension in healthy animals. Dobutamine primarily increases myocardial contractility with modest chronotropic effects and minimal impact on vascular resistance, often slightly decreasing afterload through mild beta-2 effects (Muir & Hubbell, 2014). This is often beneficial for animals with valvular insufficiency. Both drugs increase cardiac output, though through somewhat different mechanisms (Haskins, 2015). The two drugs may be combined in some clinical situations where increases in both contractility and mild vasoconstriction are deemed appropriate.
Systemic Effects #
Dopamine produces significant extracardiac effects including increased renal blood flow and sodium excretion at low doses, enhanced mesenteric perfusion, and potential increases in pulmonary vascular resistance at high doses (Pypendop & Ilkiw, 2017). Felines have little diuretic effect from dopamine due to differences in the DA1 receptor actions. Renal vasoconstriction maybe be more prominent in cats vs. dogs, but that is probably dose and condition dependent. It increases metabolic rate and may suppress prolactin secretion (Grimm et al., 2015). Dobutamine has minimal direct renal or splanchnic effects, though improved cardiac output may secondarily enhance organ perfusion. It produces less metabolic stimulation and negligible effects on pulmonary vasculature compared to dopamine (Tranquilli et al., 2015).
Clinical Applications in Veterinary Anesthesia #
Dopamine may be preferred when concurrent oliguria and hypotension are present, when both chronotropic and inotropic effects are desired, or in distributive shock requiring vascular tone support (Mazzaferro, 2017). Dobutamine is typically selected for cardiac failure, cardiogenic shock, systolic dysfunction during anesthesia, and valvular disease where tachycardia must be avoided (Epstein et al., 2015). Selection depends on the specific hemodynamic goals and concurrent pathophysiology (Posner, 2018).
Species Considerations #
Dogs generally respond predictably to both drugs, though dobutamine may be preferred in breeds prone to arrhythmias. Dopamine offers advantages when renal perfusion is a concern (Duke-Novakovski et al., 2016). The more selective cardiac effects and reduced alpha-adrenergic stimulation generally make dobutamine preferable in feline patients (Dibartola, 2014). Dobutamine may be useful as a positive chronotropic which can be carefully titrated in animals with blood pressure problems that are heart rate dependent.
Precautions and Contraindications #
Both drugs require administration via continuous rate infusion with proper dilution. Dopamine can cause tissue necrosis if extravasation occurs . Both drugs carry a risk of tachyarrhythmias and dopamine (like norepinephrine and phenylephrine) may worsen tissue perfusion at high doses through excessive vasoconstriction. It can exacerbate pulmonary hypertension at high doses (Ramsey, 2017). Dobutamine may worsen outflow obstruction in hypertrophic cardiomyopathy, increase myocardial oxygen demand, and has limited efficacy in hypovolemic states (Snyder, 2017). If either drug is initiated and response is unexpectedly poor, preload may be insufficient and fluid administration should be evaluated for appropriateness.
References #
Dibartola, S.P. (2014). Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice. Elsevier Health Sciences.
Duke-Novakovski, T., de Vries, M., & Seymour, C. (2016). BSAVA Manual of Canine and Feline Anaesthesia and Analgesia. British Small Animal Veterinary Association.
Epstein, S.E. (2015). Small Animal Critical Care Medicine. Elsevier Health Sciences.
Grimm, K.A., Lamont, L.A., Tranquilli, W.J., Greene, S.A., & Robertson, S.A. (2015). Veterinary Anesthesia and Analgesia: The Fifth Edition of Lumb and Jones. Wiley-Blackwell.
Haskins, S.C. (2015). Monitoring the critically ill dog or cat. Veterinary Clinics: Small Animal Practice, 45(5), 1001-1018.
Mazzaferro, E.M. (2017). Small Animal Emergency and Critical Care: Case Studies in Client Communication, Morbidity and Mortality. Wiley-Blackwell.
Muir, W.W., & Hubbell, J.A.E. (2014). Handbook of Veterinary Anesthesia. Mosby Elsevier.
Pascoe, P.J. (2014). The cardiopulmonary effects of dopamine hydrochloride in the anesthetized dog. Veterinary Anaesthesia and Analgesia, 41(4), 410-415.
Plumb, D.C. (2018). Plumb’s Veterinary Drug Handbook. Wiley-Blackwell.
Posner, L.P. (2018). Essentials of Small Animal Anesthesia and Analgesia. Wiley-Blackwell.
Pypendop, B.H., & Ilkiw, J.E. (2017). Cardiovascular effects of dopamine in the anesthetized cat. Veterinary Anaesthesia and Analgesia, 44(6), 1382-1388.
Ramsey, I. (2017). BSAVA Small Animal Formulary. British Small Animal Veterinary Association.
Silverstein, D.C., & Hopper, K. (2015). Small Animal Critical Care Medicine. Elsevier Health Sciences.
Snyder, L.B.C. (2017). Critical Care of the Surgical Patient, An Issue of Veterinary Clinics of North America: Small Animal Practice. Elsevier Health Sciences.
Tranquilli, W.J., Thurmon, J.C., & Grimm, K.A. (2015). Lumb and Jones’ Veterinary Anesthesia and Analgesia. Blackwell Publishing.
