Plethysmographic dynamic indices predict fluid responsiveness in septic ventilated patients

Abstract

Objectives: In septic patients, reliable non-invasive predictors of fluid responsiveness are needed. We hypothesised that the respiratory changes in the amplitude of the plethysmographic pulse wave (∆P PLET ) would allow the prediction of changes in cardiac index following volume administration in mechanically ventilated septic patients. Design: Prospective clinical investigation. Setting: An 11-bed hospital medical intensive care unit. Patients: Twenty-three deeply sedated septic patients mechanically ventilated with tidal volume ≥ 8 ml/kg and equipped with an arterial catheter and a pulse oximetry plethysmographic sensor. Interventions: Respiratory changes in pulse pressure (∆PP), ∆P PLET and cardiac index (transthoracic Doppler echocardiography) were determined before and after volume infusion of colloids (8 ml/kg). Measurements and main results: Twenty-eight volume challenges were performed in 23 patients. Before volume expansion, ∆PP correlated with ∆P PLET (r 2 = 0.71, p < 0.001). Changes in cardiac index after volume expansion significantly (p < 0.001) correlated with baseline ∆PP (r 2 = 0.76) and ∆P PLET (r 2 = 0.50). The patients were defined as responders to fluid challenge when cardiac index increased by at least 15% after the fluid challenge. Such an event occurred 18 times. Before volume challenge, a ∆PP value of 12% and a ∆P PLET value of 14% allowed discrimination between responders and non-responders with sensitivity of 100% and 94% respectively and specificity of 70% and 80% respectively. Comparison of areas under the receiver operator characteristic curves showed that ∆PP and ∆P PLET predicted similarly fluid responsiveness. Conclusion: The present study found ∆P PLET to be as accurate as ∆PP for predicting fluid responsiveness in mechanically ventilated septic patients.

Reply to the comment by Drs. Cannesson et al.

“…Cannesson et al for their kind comments regarding our contribution [1]. We fully agree with these authors that pulse oximeters use digital signal processing to make accurate measurements in clinical conditions that were otherwise impossible (e. g., patient motion, low perfusion, electrical interference).…”

Assessment of loading conditions with cardiac ultrasound. A comprehensive review

“…With transthoracic echocardiography, it is easy to demonstrate the dilation and decrease of diameter of the inferior caval vein (IVC) with inspiration and expiration, respectively. Barbier et al and M Feissel et al demonstrated clearly that respiratory variation of the IVC reliably predicts fluid responsiveness [20,21]. Conversely, in acutely decompensated heart failure patients, the rate of fluid withdrawal during haemodialysis can be guided by intermittent evaluation of the respiratory induced alterations of the IVC diameters [22].…”

Hemodynamic instability and fluid responsiveness

“…10,16 Pulse pressure variation (PPV) and systolic pressure variation (SPV)-both derived from analysis of the arterial waveform-, stroke volume variation (SVV), and the variation of the amplitude of the pulse oximeter plethysmographic waveform are predictive of fluid responsiveness. 7,21,22 These techniques use heart-lung interactions during mechanical ventilation. During inspiration, pleural pressure increases, causing a reduction in RV preload and an increase in RV afterload.…”