The Haemodynamic Effects of Dopamine and Prenalterol in Patients after Cardiac Valve Surgery

High lumbar epidural block was induced in seven dogs, causing a fall in mean arterial blood pressure (AP) from 24.5 +/- 2.9 to 12.0 +/- 3.1 kPa owing to reductions in cardiac output (QT) and systemic vascular resistance (SVR) to 67% and 68% of the pre-epidural values. Volume loading with dextran 10 ml X kg-1 b.w. increased QT nearly to the pre-epidural value. SVR decreased further to 61% of the pre-epidural value and AP was only slightly increased to 14.9 +/- 2.7 kPa. Subsequent administration of prenalterol 20 micrograms X kg-1 b.w. caused a further increase in QT to 17% above the pre-epidural value due to an increase in heart rate of 51 beats/min. AP did not change since SVR decreased further to 49% of the pre-epidural value. The hepatic arterial blood flow (QHA) was essentially unchanged during epidural block as well as during volume loading, while the portal venous blood flow (Qpv) was changed concurrently with (QT). In spite of the decrease in SVR, the preportal and hepatic arterial vascular resistances were not diminished following prenalterol. The increase in OT must therefore have favoured other vascular beds. Hepatic and pre-portal tissue oxygen uptakes were unchanged during the experimental procedure, while whole-body oxygen uptake decreased by 20% following the epidural block and increased nearly to the pre-epidural level following volume loading in combination with prenalterol.

Section: Cenlral Haemodynamicssupporting

confidence: 69%

Effects of Prenalterol and Volume Loading with Dextran on Haemodynamics and Oxygen Consumption in Dogs During High Epidural Block with Special Reference to the Splanchnic Region

Greitz

Andreen

Irestedt

1985

Dopamine versus Dobutamine after Open‐Heart Surgery

Tydén

Nyström

1983

The haemodynamic effects of dopamine and dobutamine were compared in a cross-over study of 12 patients in the early postoperative phase after open-heart surgery. The drug infusion rates (dopamine (microgram/kg/min) mean 6.5, range 2.8-12, dobutamine (microgram/kg/min) mean 7.9, range 4.3-12.3) were adjusted so that the cardiac output increased by 50%. With both drugs this was achieved through simultaneous increases in stroke volume (dopamine + 16%, dobutamine + 9%) and heart rate (dopamine + 31%, dobutamine + 38%). The systemic vascular resistance did not change with dopamine but decreased significantly (-18%) with dobutamine. Therefore, the systolic and diastolic arterial blood pressures rose significantly more with dopamine than with dobutamine. The left atrial pressure increased with dopamine but was unchanged with dobutamine. The urine output was significantly higher with dopamine than with dobutamine.

Haemodynamic Comparison of Dopamine and Dobutamine in Normovolaemic and Hypovolaemic Dogs

Vainionpää

Nuutinen

Kairaluoma

et al. 1983

The haemodynamic effects of dopamine and dobutamine in doses of 1-106 micrograms/kg/min were compared in dogs, first in the normovolaemic state and then after bleeding (10 ml/kg). In normovolaemia, dopamine caused a dose-dependent rise in systolic, mean and diastolic aortic pressures, while dobutamine caused a rise only in systolic pressure. In hypovolaemia, a rise in all three aortic pressures, was caused by both drugs, but to a lesser extent by dobutamine. Heart rate and cardiac output were similarly increased by both drugs, as was pulmonary artery pressure with high doses, in both states. Renal blood flow and diuresis increased in the middle-dose area. Both inotropic drugs caused an elevation in Paco2 and a drop in Pao2 and O2-saturation in both normovolaemia and hypovolaemia. The results agree with current opinion on the dose-dependent alpha-sympathomimetic action of dopamine and the relatively pure beta-action of dobutamine.