Predicting fluid responsiveness in mechanically ventilated children under general anaesthesia using dynamic parameters and transthoracic echocardiography

Background. Dynamic variables are accurate predictors of fluid responsiveness in adults undergoing mechanical ventilation. They can be determined using respiratory variation in aortic flow peak velocity (Delta Vpeak), arterial pulse pressure [Delta PP and pulse pressure variation (PPV)], or plethysmographic waveform amplitude [Delta POP and pleth variability index (PVI)]. These indices have not been validated in children. We studied the ability of these variables to predict fluid responsiveness in mechanically ventilated children. Methods. All results are expressed as median [median absolute deviation (MAD)]. Thirty mechanically ventilated children were studied after undergoing general anaesthesia. Mechanical ventilation was maintained with a tidal volume of 10 ml kg(-1) of body weight. Delta PP, PPV, Delta POP, PVI, Delta Vpeak, and aortic velocity-time integral were recorded before and after volume expansion (VE). Patients were considered to be responders to VE when the aortic velocity-time integral increased more than 15% after VE. Results. VE induced significant changes in Delta PP [13 (MAD 4) to 9 (5)%], PPV [15 (5) to 9 (5)%], Delta POP [15 (10) to 10 (6)%], PVI [13 (6) to 8 (5)%], and Delta Vpeak [16 (9) to 8 (3)%] (P < 0.05 for all). Differences in Delta PP, Delta POP, PPV, and PVI did not reach statistical significance. Only Delta Vpeak was significantly different between responders (R) and non-responders (NR) to VE [22 (3) vs 7 (1)%, respectively; P < 0.001]. The threshold Delta Vpeak value of 10% allowed discrimination between R and NR. Conclusions. In this study, Delta Vpeak was the most appropriate variable to predict fluid responsiveness.