Respiratory variations in aortic blood flow predict fluid responsiveness in ventilated children

Objective: To investigate whether respiratory variations in aortic blood flow velocity (Delta Vpeak ao), systolic arterial pressure (Delta PS) and pulse pressure (Delta PP) could accurately predict fluid responsiveness in ventilated children. Design and setting: Prospective study in a 18-bed pediatric intensive care unit. Patients: Twenty-six children [median age 28.5 (16-44) months] with preserved left ventricular (LV) function. Intervention:Standardized volume expansion (VE). Measurements and main results: Analysis of aortic blood flow by transthoracic pulsed-Doppler allowed LV stroke volume measurement and on-line Delta Vpeak ao calculation. The VE-induced increase in LV stroke volume was > 15% in 18 patients (responders) and < 15% in 8 (non-responders). Before VE, the Delta Vpeak ao in responders was higher than that in non-responders [19% (12.1-26.3) vs. 9% (7.3-11.8), p = 0.001], whereas Delta PP and Delta PS did not significantly differ between groups. The prediction of fluid responsiveness was higher with Delta Vpeak ao [ROC curve area 0.85 (95% IC 0.99-1.8), p = 0.001] than with Delta PS (0.64) or Delta PP (0.59). The best cut-off for Delta Vpeak ao was 12%, with sensitivity, specificity, and positive and negative predictive values of 81.2%, 85.7%, 93% and 66.6%, respectively. A positive linear correlation was found between baseline Delta Vpeak ao and VE-induced gain in stroke volume (rho = 0.68, p = 0.001). Conclusions: While respiratory variations in aortic blood flow velocity measured by pulsed Doppler before VE accurately predict the effects of VE, Delta PS and Delta PP are of little value in ventilated children.