Stroke volume variation compared with pulse pressure variation and cardiac index changes for prediction of fluid responsiveness in mechanically ventilated patients

Introduction

Adequate volume resuscitation is very important for a favorable outcome of critically ill patients. Both over and under filling of intravascular volume could be deleterious. Static indices including central venous pressure, pulmonary capillary wedge pressure, left ventricular end-diastolic area, mean arterial pressure (MAP) and tachycardia are commonly used and are known to be of little value in discriminating responders from non-responders. On the other hand dynamic indices such as pulse pressure variation (PPV), inferior vena cava diameter, superior vena cava diameter, aortic blood flow, which are based on variation on the left ventricular stoke volume, have been shown to be more accurate predictors of fluid responsiveness in mechanically ventilated patients. In this study we are evaluating the ability of stroke volume variation (SVV) obtained by Vigileo–FloTrac device to predict fluid responsiveness in patients with acute circulatory failure under complete passive, volume controlled mechanical ventilation and correlating it to manually calculated PPV.

Materials and methods

Twenty five patients aged above 18 years, with acute circulatory failure and at least one sign of tissue hypoperfusion requiring fluid resuscitation and mechanical ventilation were included. Excluded are patients with cardiogenic shock, acute pulmonary edema, LVEF <50%, atrial fibrillation, frequent ectopics, significant aortic or mitral valve abnormalities or renal failure. Candidates were subjected to thorough clinical evaluation, lab investigation and ECG. Following sedation, muscle relaxation and maintenance of mean arterial pressure >65 mmHg by norepinephrine, 500 ml of Hes-steril were administered over 10 min. Static and dynamic hemodynamic parameters were taken in supine position before and after fluid challenge. Patients who had an increase of cardiac index measured by trans-thoracic echocardiography ⩾15% of baseline measurement were considered responders.

Results

Fourteen patients were fluid responders. Before fluid challenge SVV and PPV were significantly higher in responders than non-responders (p = 0.0001 for each). SVV ⩾ 8.15% predicted responders with a sensitivity of 100% and specificity 81.1% (AUC 0.906). PPV ⩾ 10.2 also predicted responders with a sensitivity of 92.9% and specificity of 90.9% (AUC 0.974). The higher the SVV before fluid challenge the higher the percentage of increase of CI following fluid challenge (r = 0.733, p = 0.00). PPV showed the same correlation pattern with percentage increase of CI (r = 0.798, p = 0.00).

Conclusions

Baseline stroke volume variation ⩾8.15% predicted fluid responsiveness in mechanically ventilated patients with acute circulatory failure. The study also confirmed the ability of pulse pressure variation to predict fluid responsiveness.