The Validity of Peripheral Perfusion Index to Predict Fluid Responsiveness

The concept of fluid responsiveness has been suggested to guide fluid administration in critically ill patients to avoid either over or under-transfusion.

Several methods have been suggested to detect fluid responsiveness. Mini fluid challenge with concomitant monitoring of stroke volume is one of the most robust methods for pre-load challenge.

The main foreshortening of mini fluid challenge method is the need for a real-time cardiac output monitor, to track the instantaneous change of stroke vole with changing body position. Finding a surrogate to cardiac output to trace the effect of mini fluid challenge would make the test more applicable without the need for advanced hemodynamic monitors.

There is a growing interest in the use of perfusion indices in assessment of fluid responsiveness. Perfusion indices are measures for adequacy of oxygen delivery in peripheral tissues; thus, they were hypothesized to be possible surrogates of cardiac output. Peripheral perfusion index represents "the ratio between the pulsatile and non-pulsatile component of the light reaching the pulse oximeter" . Peripheral perfusion index has been considered as a numerical non-invasive measure for peripheral perfusion. PPI has the advantage over other perfusion indices that it a non-invasive, user-friendly monitor.

The aim of this work is to investigate the ability of peripheral perfusion index to predict the hemodynamic response to mini-fluid challenge in patients with septic shock.

Mini-fluid challenge test will be performed by infusion of 200 mL Lactated Ringer's solution over 1 minute. Velocity time integral will be monitored using Transthoracic echocardiography at the left ventricular outflow tract at the apical five-chamber view. Cardiac output will be calculated, and the patient will be considered fluid-responder if cardiac output increased by 10% after fluid challenge.