Heterogeneity and prediction of hemodynamic responses to dobutamine in patients with septic shock

Objective: To establish the heterogeneity of hemodynamic responses to dobutamine in patients with septic shock and to identify the predictive factors of these hemodynamic responses. Design: Prospective study. Setting and Patients: A total of 12 patients with septic shock in a tertiary medical intensive care unit. Interventions: A 20-min dobutamine infusion at 5 mu g.kg(-1).min(-1) with subsequent increments to 8, 12.6, and 20 mu g.kg(-1).min(-1), on two consecutive days. Responses were dichotomized into changes in heart rate (HR) or stroke volume index (SVI) of >10% and <= 10% at the maximal dobutamine infusion. Measurements and Main Results: No differences were found in survival, Acute Physiology and Chronic Health Evaluation II score, maximal dobutamine doses, or pharmacokinetics of dobutamine between HR and SVI groups. In Delta HR > 10% vs. Delta HR <= 10%, baseline HR was lower, and baseline mixed venous oxygen tension and saturation were higher. During dobutamine infusion, mean arterial pressure decreased in Delta HR > 10%. Cardiac index and the systemic oxygen delivery index increased and the systemic vascular resistance index decreased at unchanged SVI. Pressure work index increased and the ratio of the diastolic to systolic aortic pressure time indices decreased but not to <0.6. In Delta HR <= 10%, systemic vascular resistance index and the ratio of the diastolic to systolic aortic pressure time indices decreased (but remained >0.6) without changes in SVI or cardiac index. Baseline hemodynamic and metabolic variables did not differ between SVI groups. In Delta SVI > 10%, cardiac index increased with dobutamine, but PaO2 and the systemic oxygen delivery index decreased. In Delta SVI <= 10%, HR and the systemic oxygen delivery index increased; mean arterial pressure, left ventricular stroke work index, systemic vascular resistance index, and the ratio of the diastolic to systolic aortic pressure time indices decreased. Conclusions: Patients with a positive chronotropic response to dobutamine had lower baseline HR values, and a chronotropic rather than inotropic response predicted an increase in cardiac index and systemic oxygen delivery index. Incremental dosages of dobutamine did not compromise indirectly measured myocardial oxygen balance.