Variability in the Hemodynamic Response to Fluid Bolus in Pediatric Septic Shock

Fluid boluses are commonly administered to improve the cardiac output and tissue oxygen delivery in pediatric septic shock. The objective of this study is to evaluate the effect of an early fluid bolus administered to children with septic shock on the cardiac index and mean arterial pressure, as well as on the hemodynamic response and its relationship with outcome.

We prospectively collected hemodynamic data from children with septic shock presenting to the emergency department or the PICU who received a fluid bolus (10 mL/kg of Ringers Lactate over 30 min). A clinically significant response in cardiac index-responder and mean arterial pressure-responder was both defined as an increase of greater than or equal to 10% 10 minutes after fluid bolus.

Forty-two children with septic shock, 1 month to 16 years old, median Pediatric Risk of Mortality-III of 13 (interquartile range, 9-19), of whom 66% were hypotensive and received fluid bolus within the first hour of shock recognition. Cardiac index- and mean arterial pressure-responsiveness rates were 31% and 38%, respectively. We failed to identify any association between cardiac index and mean arterial pressure changes (r = 0.203; p = 0.196). Cardiac function was similar in mean arterial pressure- and cardiac index-responders and nonresponders. Mean arterial pressure-responders increased systolic, diastolic, and perfusion pressures (mean arterial pressure - central venous pressure) after fluid bolus due to higher indexed systemic vascular resistance and arterial elastance index. Mean arterial pressure-nonresponders required greater vasoactive-inotrope support and had higher mortality.

The hemodynamic response to fluid bolus in pediatric septic shock was variable and unpredictable. We failed to find a relationship between mean arterial pressure and cardiac index changes. The adverse effects of fluid bolus extended beyond fluid overload and, in some cases, was associated with reduced mean arterial pressure, perfusion pressures and higher vasoactive support. Mean arterial pressure-nonresponders had increased mortality. The response to the initial fluid bolus may be helpful to understand each patient's individualized physiologic response and guide continued hemodynamic management.