Pleth Variability Index: An Insight into Its Benefits and Limitations as a Predictor of Fluid Responsiveness
Suhreet Manandhar, Zi Jun Liu*
Department of General Surgery, Nanjing First Hospital Affiliated to Nanjing Medical University, Chang Le Road, 68-Nanjing, Jiangsu, China
An important step in the management of surgical and critically ill patients is fluid and electrolyte balance as hypovolemia, hypervolemia and electrolyte imbalance can cause poor patient outcomes. The ability to distinguish between fluid responders and non-responders help us to avoid complications of fluid imbalance. Dynamic measures have been considered reliable than static measures to predict the fluid response. However, most dynamic measures are invasive with associated complications. The recent studies have reported that respiratory variations in plethysmographic waveform amplitude (?POP) are strongly linked with pulse pressure variation and hence can be used in predicting fluid response. This has led to pleth variability index (PVI), a dynamic measure developed by Masimo Corporation, which is closely related to ?POP and can noninvasively measure the dynamic variations of perfusion index (PI). It has benefited clinicians in distinguishing fluid responders from non-responders in surgical and critically ill patients under mechanical ventilation. Numerous studies have reported PVI as a dependable predictor of fluid responsiveness on par with pulse pressure variation (PPV) and stroke volume variation (SVV). PVI also provides the added benefits of predicting hypotension, especially in patients during anesthesia and also in selecting appropriate positive end expiratory pressure (PEEP) in patients under ventilator support, thus, helping to improve patient clinical outcomes. However, PVI has been reported to be erratic in predicting fluid response in spontaneously breathing patients, patients undergoing laparoscopic and cardiac surgery, and patients with low perfusion index, low tidal volume (<8 ml/kg) and cardiac arrhythmias.