[Coupling of cardiac output or systemic O2 transport and metabolism during catecholamine therapy]

Catecholamines increase cardiac output (CO) and thus systemic oxygen delivery, but they also increase the tissue's oxygen demand (thermogenic or calorigenic effect). Therefore, it is of particular interest for the choice of a catecholamine as to what extent CO is increased in relation to oxygen demand (VO2), because the tissue's oxygen balance is improved only if CO and thus oxygen delivery increases more than oxygen demand. For this purpose we reviewed the literature and analysed the relation between CO and VO2 during physiological as well as during pathological conditions. In particular, we compared the slopes of the regression lines of the individual CO/VO2-relation for each catecholamine. Dependent on study conditions, the extent of the increases in CO and VO2 varies substantially already for one and the same agent. During physiological conditions, the synthetic agents dobutamine and dopexamine primarily increase CO, whereas the endogenous ones epinephrine and particularly norepinephrine increase both CO and VO2 to about the same extent. During pathological conditions the literature is inconsistent, but it appears that the CO/VO2-relations do not differ substantially from those observed under physiological conditions. With due caution the current information implies that the synthetic catecholamines dobutamine and in particular dopexamine might be preferred in the treatment of low cardiac output states because they increase CO and thus oxygen delivery above the increase in metabolic demand.