Comparative haemodynamic effects of dopamine and dobutamine in septic shock

Septic shock associated with depressed myocardial function generally requires the use of catecholamine. Currently dopamine is often selected. Dobutamine is a newly developed catecholamine which has been shown to be of value in severe cardiomyopathic disease. The aim of this work was to determine the most appropriate drug by comparing haemodynamic responses to dopamine and dobutamine in 19 studies carried out in 11 patients with septic shock and heart failure. Cardiac index increased similarly with dopamine and dobutamine (33%), as did stroke volume (respectively 26.4 and 25%). Arterial pressure increased by 17% with dopamine whereas it did not significantly change with dobutamine due to reduction in vascular resistance of 19%. Dobutamine decreased filling pressure, either right (14%) or left (28%) whilst they slightly but unsignificantly increased with dopamine. Pulmonary shunting increased more with dopamine (47%) than with dobutamine (16%), but PaO₂ remained constant with both. Since septic shock is characterized by lowered arterial pressure and vasodilatation it is concluded that effects of dopamine on capacitance and resistance vessels make this drug more suitable. In addition it selectively increases renal blood flow. Nevertheless dobutamine could be appropriate, in case of very high filling pressures, severe peripheral vasoconstriction, marked pulmonary shunting and in some cases where dopamine becomes ineffective.