Dose range is 0 5-25 micrograms kg-1 per minute. Dopamine stimulates adrenoreceptors and dopaminergic receptors. The effects of dopamine change with increasing dose.
At low doses (up to 3 micrograms kg-1 per minute) the predominant effects are those of dopaminergic stimulation causing an increase in renal and mesenteric blood flow. Between doses of 2 5 and 10 micrograms kg-1 per minute, pi receptor effects predominate causing increased myocardial contractility, heart rate, and cardiac output. At doses >10 micrograms kg-1 per minute, a stimulation predominates, causing a rise in systemic vascular resistance and reduction in renal blood flow. High doses of dopamine are associated with arrhythmias and increased myocardial oxygen demand.
It has been shown that there is marked individual variation in plasma level compared with dose in the critically ill, making it difficult to know which effects are predominating. Dopamine may accumulate in patients with hepatic dysfunction. There is no evidence to justify using low dose dopamine in acute renal failure either as prevention or treatment (see Chapter 8). The indications for and disadvantages of dopamine are given in Box 6.4.
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