Hemodynamic Effects of Dopamine during Thoracic Epidural Analgesia in Man

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Abstract
The cardiovascular effects of dopamine were studied before and during thoracic epidural analgesia (TEA) in eight patients prior to abdominal aortic surgery. Dopamine was infused at rates of 2, 4, and 8 .mu.g .cntdot. kg-1 .cntdot. min-1. Mean plasma dopamine concentration increased proportionally to the infusion rate. Before TEA, dopamine 8 .mu.g .cntdot. kg-1 .cntdot. min-1 decreased systemic vascular resistance 4 .+-. 4 mmHg min .cntdot. l-1 (m .+-. SD) (P < 0.05), but increased mean arterial pressure 15 .+-. 12 mmHg (P < 0.01), cardiac output 1.9 .+-. 1.0 l .cntdot. min-1 (P < 0.01), heart rate 10 .+-. 9 beats .cntdot. min-1 (P < 0.05), and plasma norepinephrine concentration 544 .+-. 252 pg .cntdot. ml-1 (P < 0.01). After the induction of TEA, which extended above the T2 dermatome and below the L2 dermatome, saline and albumin were infused to maintain central venous and pulmonary capillary wedge pressures. TEA reduced mean arterial pressure from 96 .+-. 18 to 55 .+-. 8 mmHg (P < 0.01), cardiac output from 4.7 .+-. 0.9 to 3.9 .+-. 0.9 l .cntdot. min-1 (P = 0.05), systemic vascular resistance from 21 .+-. 6 to 14 .+-. 3 mmHg min .cntdot. l-1 (P < 0.05), and plasma norepinephrine concentration from 394 .+-. 141 to 207 .+-. 73 pg .cntdot. ml-1 (P < 0.010. The plasma epinephrine concentration was reduced 49% after the induction of TEA. During TEA, dopamine, 8 .mu.g .cntdot. kg-1 .cntdot. min-1 increased mean arterial pressure by 57 .+-. 9 mmHg (P < 0.01), cardiac output by 2.9 .+-. 0.8 l .cntdot. min-1 (P < 0.01), heart rate by 14 .+-. 11 beats .cntdot. min-1 (P < 0.01), and plasma norepinephrine concentration by 833 .+-. 499 pg .cntdot. ml-1 (P < 0.01). Systemic vascular resistance changed in a diphasic fashion. Thus, at 2 .mu.g .cntdot. kg-1 .cntdot. min-1 of dopamine, the value decreased further, below the level seen with TEA alone, but increased at 4 and 8 .mu.g .cntdot. kg-1 .cntdot. min-1. In addition, at 8 .mu.g .cntdot. kg-1 .cntdot. min-1, mean pulmonary artery pressure and pulmonary capillary wedge pressure were greater during than before TEA, although the values were similar without dopamine. The authors conclude that the effects of dopamine on mean arterial pressure, cardiac output, systemic vascular resistance, pulmonary capillary wedge, and mean pulmonary artery pressure were different during TEA, as compared to before the block. A moderate dose of dopamine (4 .mu.g .cntdot. kg-1 .cntdot. min-1) was sufficient to maintain arterial pressure and cardiac output at adequate levels during TEA although systemic vascular resistance remained low.
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