Cardiovascular response to dobutamine stress predicts outcome in severe sepsis and septic shock

During septic shock, resistance to the haemodynamic effects of catecholamine vasopressors and inotropes is a well-recognised marker of mortality risk. However, the specific cardiovascular or metabolic response elements that are most closely associated with outcome have not been well defined. The objective of this study was to assess cardiovascular and metabolic responses to dobutamine as correlates of outcome in patients with severe sepsis or septic shock.

A prospective, non-randomised, non-blinded interventional study of graded dobutamine challenge (0, 5, 10, and 15 mug/kg/min) in adult patients who had undergone pulmonary artery catheterisation within 48 hours of onset of severe sepsis or septic shock (8 survivors/15 non-survivors) was performed. Radionuclide cineangiography during graded infusion was used to determine biventricular ejection fractions at each increment of dobutamine.

In univariate analysis, a variety of cardiovascular or haemodynamic and oxygen transport or metabolic variables (at the point of maximum cardiac index response for a given subject) were associated with survival including: increased stroke volume index (p = 0.0003); right ventricular end-diastolic volume index (p = 0.0047); left ventricular stroke work index (p = 0.0054); oxygen delivery index (p = 0.0084); cardiac index (p = 0.0093); systolic blood pressure/left ventricular end-systolic volume index ratio (p = 0.0188); left ventricular ejection fraction (p = 0.0160); venous oxygen content (p = 0.0208); mixed venous oxygen saturation (p = 0.0234); pulse pressure (p = 0.0403); decreased pulmonary artery diastolic pressure (p = 0.0133); systemic vascular resistance index (p = 0.0154); extraction ratio (p = 0.0160); and pulmonary vascular resistance index (p = 0.0390). Increases of stroke volume index of greater than or less than 8.5 mL/m2 were concordant with survival or death in 21 of 23 cases. Multivariate profile construction showed stroke volume index as the dominant discriminating variable for survival with the systolic blood pressure/left ventricular end-systolic volume index ratio alone among all other variables significantly improving the model.

Survivors maintain cardiac responsiveness to catecholamine stimulation during septic shock. Survival from severe sepsis or septic shock is associated with increased cardiac performance and contractility indices during dobutamine infusion. Further studies are required to determine whether these parameters are predictive of outcome in a larger severe sepsis/septic shock population.