多巴胺
多巴胺是一種內源性**兒茶酚胺**，也是去甲腎上腺素的直接代謝前體。在獸醫重症監護中，主要在充分的液體復甦*之後*，作為連續靜脈輸注 (CRI) 用於控制血流動力學不穩定，特別是低血壓休克和急性心臟衰竭。 ### 臨床重點 * **劑量依賴性效應**：多巴胺的受體親和力會根據輸注速率發生顯著變化，從多巴胺能（血管擴張）進展到 β-1（正性肌力），再到 α-1（升壓）效應。 * **腎臟劑量爭議**：過去常使用「低劑量」多巴胺來促進少尿型急性腎損傷的利尿。現代證據表明它並不能顯著改善腎小球濾過率 (GFR)，在犬隻中的應用被認為未經證實或存在爭議，對貓甚至可能有害。 * **嚴格的給藥規則**：必須透過專用靜脈管線並使用注射幫浦或輸液幫浦給藥。**藥物外滲**會導致嚴重的組織壞死。
作用機制: Dopamine acts directly on **dopaminergic**, **β1-adrenergic**, and **α1-adrenergic** receptors, and indirectly by stimulating the release of endogenous norepinephrine from sympathetic nerve terminals. Its effects are highly dose-dependent: * **Low Dose (0.5–2 µg/kg/min)**: Primarily stimulates **D1 and D2 dopaminergic receptors** → vasodilation of renal, mesenteric, coronary, and intracerebral vascular beds. Increases renal blood flow and urine output, but does not appreciably increase GFR. * **Medium Dose (2–10 µg/kg/min)**: Stimulates **β1-adrenergic receptors** in the myocardium → increases intracellular cAMP → positive inotropic (increased contractility) and mild chronotropic (increased heart rate) effects. Improves cardiac output and organ perfusion. * **High Dose (>10–12 µg/kg/min)**: Overrides dopaminergic effects and strongly stimulates **α1-adrenergic receptors** in the vasculature → profound vasoconstriction → increases systemic vascular resistance (SVR) and blood pressure. Renal and peripheral blood flows are decreased at these rates.
各物種劑量
- Vasodilatory shock if fluid resuscitation and dobutamine is not successful · 2.5-10 micrograms/kg/min · IV · CRI · Titrated to effect · If not successful may try adding norepinephrine.
- Treatment of severe hypotension/shock · 1-3 micrograms/kg/minute CRI; higher dosages of 3-10 micrograms/kg/min CRI are indicated if greater cardiotonic and BP support are indicated · IV · CRI · Titrated to effect · Not a substitute for adequate volume replacement therapy.
- Treatment of severe hypotension/shock after fluid correction and if dobutamine does not give desired effect · 1-10 micrograms/kg/min · IV · CRI · Titrated to effect
- Vasodilatory shock if fluid resuscitation and dobutamine is not successful · 2.5-10 micrograms/kg/min · IV · CRI · Titrated to effect · If not successful may try adding norepinephrine.
- Adjunctive therapy for acute heart failure · 1-10 micrograms/kg/min · IV · CRI · Titrated to effect · Initially, a dose of 2 micrograms/kg/min is usually used and titrated upward to desired clinical effect. Doses higher than 10 may increase peripheral vascular resistance and heart rate.
- Treatment of severe hypotension/shock · 1-3 micrograms/kg/minute CRI; higher dosages of 3-10 micrograms/kg/min CRI are indicated if greater cardiotonic and BP support are indicated · IV · CRI · Titrated to effect · Not a substitute for adequate volume replacement therapy.
- Treatment of severe hypotension/shock after fluid correction and if dobutamine does not give desired effect · 1-10 micrograms/kg/min · IV · CRI · Titrated to effect
給藥途徑
禁忌症
- Pheochromocytoma
- Ventricular fibrillation
- Uncorrected tachyarrhythmias
- Uncorrected hypovolemia (must replace fluids first)
不良反應
- Nausea and vomiting
- Ectopic beats (arrhythmias)
- Tachycardia
- Palpitations
- Hypotension (at low doses) or Hypertension (at high doses)
- Dyspnea
- Vasoconstriction (reduced peripheral circulation)
- Severe tissue necrosis and sloughing (if extravasated)
藥物相互作用
- Alpha-adrenergic blockers (e.g., prazosin) · May antagonize the vasoconstrictive properties of high-dose dopamine.
- Halogenated hydrocarbon anesthetics (e.g., halothane) · May result in increased incidences of ventricular arrhythmias.
- Tricyclic antidepressants · May potentiate adverse cardiovascular effects.
- Beta-blockers (e.g., propranolol, metoprolol) · May antagonize the cardiac (inotropic/chronotropic) effects of dopamine.
- Diuretics · May potentiate urine production effects of low-dose dopamine.
- Monoamine oxidase inhibitors (MAOIs) · Can significantly prolong and enhance the effects of dopamine.
- Oxytocic drugs · May cause severe hypertension when used concurrently.
- Phenothiazines · May antagonize the renal and mesenteric vasodilatation effects of dopamine.
- Vasopressors/Vasoconstrictors · Concurrent use may cause severe hypertension.
監測
- Continuous electrocardiogram (ECG) for cardiac rate and rhythm
- Direct or indirect blood pressure
- Urine output/flow
- IV catheter site (frequent checks for patency and signs of extravasation)
過量
Accidental overdosage is primarily manifested by **excessive blood pressure elevation** (severe hypertension) and arrhythmias. * **Treatment**: Because dopamine's half-life is extremely short (~2 minutes), treatment usually consists only of temporarily discontinuing the IV infusion or reducing the rate until parameters normalize. * If the patient's condition fails to stabilize rapidly after discontinuation, the alpha-adrenergic antagonist **phentolamine** may be administered.
VetSheet 藥物參考供持牌獸醫專業人員作臨床決策輔助之用,不能取代專業判斷或廠方最新藥品說明書。