Pulse oximetry wave variation as a noninvasive tool to assess volume status in cardiac surgery

ABSTRACT

OBJECTIVE: To compare variations of plethysmographic wave amplitude (ÃPpleth) and to determine the percent difference between inspiratory and expiratory pulse pressure (ÃPp) cutoff values for volume responsiveness in a homogenous population of postoperative cardiac surgery patients. INTRODUCTION: Intra-thoracic pressure variations interfere with stroke volume variation. Pulse pressure variations through arterial lines during mechanical ventilation have been recommended for the estimation of fluid responsiveness. Pulse oximetry may offer a non-invasive plethysmographic method to evaluate pulse pressure; this may be useful for guiding fluid replacement. METHODS: Controlled, prospective study in cardiac surgery patients under controlled ventilation. Simultaneous digital recordings of arterial pressure and plethysmographic waves were performed. ÃPp, systolic pressure (ÃPs), DPpleth, and systolic component (ÃSpleth) were calculated. A DPp > 13 percent identified fluid-responsive patients. Volume expansion was performed in responsive subjects. Systolic and amplitude components of pressure and plethysmographic waves were compared. RESULTS: In 50 measurements from 43 patients, ÃPp was correlated with (Ppleth (r=0.90, p<0.001), (Ps (r=0.90, p<0.001), and (Spleth (r=0.73, p<0.001). An aArea under ROC curve (AUC) identified the fluid responsiveness thresholds: (Ppleth of 11 percent (AUC = 0.95±0.04), (Ps of 8 percent (AUC=0.93±0.05), and (Spleth of 32 percent (AUC=0.82±0.07). A (Ppleth value > 11 percent predicted (Pp > 13 percent with 100 percent specificity and 91 percent sensitivity. Volume expansion, performed in 20 patients, changed (Pp, (Ppleth, (Ps and (Spleth significantly (p<0.008). CONCLUSIONS: ÃPpleth is well correlated with DPp and constitutes a simple and non-invasive method for assessing fluid responsiveness in patients following cardiac surgery.