Pulse pressure variation and prediction of fluid responsiveness in patients ventilated with low tidal volumes.
OBJECTIVE
To determine the utility of pulse pressure variation (ΔRESP PP) in predicting fluid responsiveness in patients ventilated with low tidal volumes (V T) and to investigate whether a lower ΔRESP PP cut-off value should be used when patients are ventilated with low tidal volumes.


METHODS
This cross-sectional observational study included 37 critically ill patients with acute circulatory failure who required fluid challenge. The patients were sedated and mechanically ventilated with a V T of 6-7 ml/kg ideal body weight, which was monitored with a pulmonary artery catheter and an arterial line. The mechanical ventilation and hemodynamic parameters, including ΔRESP PP, were measured before and after fluid challenge with 1,000 ml crystalloids or 500 ml colloids. Fluid responsiveness was defined as an increase in the cardiac index of at least 15%. ClinicalTrial.gov: NCT01569308.


RESULTS
A total of 17 patients were classified as responders. Analysis of the area under the ROC curve (AUC) showed that the optimal cut-off point for ΔRESP PP to predict fluid responsiveness was 10% (AUC = 0.74). Adjustment of the ΔRESP PP to account for driving pressure did not improve the accuracy (AUC = 0.76). A ΔRESP PP ≥ 10% was a better predictor of fluid responsiveness than central venous pressure (AUC = 0.57) or pulmonary wedge pressure (AUC = 051). Of the 37 patients, 25 were in septic shock. The AUC for ΔRESP PP ≥ 10% to predict responsiveness in patients with septic shock was 0.484 (sensitivity, 78%; specificity, 93%).


CONCLUSIONS
The parameter D RESP PP has limited value in predicting fluid responsiveness in patients who are ventilated with low tidal volumes, but a ΔRESP PP>10% is a significant improvement over static parameters. A ΔRESP PP ≥ 10% may be particularly useful for identifying responders in patients with septic shock.
Universidade Federal do Rio Grande do Sul, Hospital de Clínicas de Porto Alegre, Department of Intensive Care Medicine, Porto Alegre/RS, Brazil.
Clarice Daniele Alves de
CD
Oliveira-Costa
Gilberto
G
Friedman
Sílvia Regina Rios
SR
Vieira
Léa
L
Fialkow
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure / Q000502:physiology*; D001810:Blood Volume / Q000502:physiology*; D002302:Cardiac Output / Q000502:physiology; D016638:Critical Illness; D003430:Cross-Sectional Studies; D005260:Female; D005440:Fluid Therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012372:ROC Curve; D012121:Respiration, Artificial / Q000379:methods*; D012772:Shock, Septic / Q000503:physiopathology; D013990:Tidal Volume / Q000502:physiology*; D055815:Young Adult