Feb 2 2011
Masimo announced today that a new study published in the peer-reviewed journal Critical Care Medicine demonstrates that noninvasive, continuous monitoring of Masimo Pleth Variability Index (PVI®) predicts fluid responsiveness with high sensitivity (95%) and specificity (91%) in mechanically-ventilated patients in the Intensive Care Unit (ICU). Multiple previous studies have shown that PVI predicts fluid responsiveness in surgical patients—helping clinicians improve fluid management to reduce patient risk, but this is the first published study demonstrating its effectiveness in predicting fluid responsiveness in critically-ill ICU patients.
Hemodynamic instability is a common problem for critically-ill patients, but the decision to administer fluid in an attempt to improve cardiac output is challenging. When necessary, fluid administration is critical to optimizing patient status and enabling end organ preservation, but unnecessary fluid administration is associated with increased morbidity and mortality. However, other dynamic indicators for assessing intravascular fluid volume are either invasive, operator dependent, costly, or unreliable predictors of whether a patient will benefit from fluid administration.
Citing numerous prospective studies showing that "only half of critically-ill patients respond to fluid boluses deemed necessary by attending physicians," researchers from CHU de Poitiers (France) acknowledged the "need for simple, noninvasive, and continuous bedside monitoring capable of detecting fluid responsiveness early in virtually all ICU patients, including those without an arterial catheter" in undertaking the current study. PVI provides clinicians with a noninvasive, continuous, and cost-effective measure for assessing whether patients will benefit from fluid administration—enabling clinicians to provide personalized and goal-directed fluid therapy(1, 2, 3, 4).
To evaluate the predictive ability of fluid responsiveness indicators, study researchers compared three indices in 40 mechanically-ventilated patients with circulatory insufficiency in the ICU. The indices ranged in level of difficulty to perform—from automatic (PVI, noninvasively obtained via the Masimo Radical-7 Pulse CO-Oximeter) to invasive (DeltaPP, respiratory variations in arterial pulse pressure obtained via arterial catheter) to operator-dependent (CO, cardiac output obtained via echocardiography). Each of the indices was recorded before and after fluid challenge, which consisted of either 500mL of 130/0.4 hydroxyethyl-starch (fluid) infused over 10 minutes with the patient in a semi-recumbent position (head at 45 degrees) or passive leg raising (PLR) if DeltaPP <13%—indicating that the patient would be unlikely to respond to fluid administration.
Results showed 21 patients (19 fluid, 2 PLR) were responders—defined as an increase in cardiac output of >15% after fluid or PLR—and 19 patients (2 fluid, 17 PLR) were non-responders. A threshold value of 17% for PVI allowed discrimination between responders and non-responders at 95% sensitivity and 91% specificity and a DeltaPP threshold value of 10% allowed discrimination between responders and non-responders at 100% sensitivity and 95% specificity. However, cardiac output (CO) was unable to reliably predict responders vs. non-responders. Additionally, responders had significantly higher average values vs. non-responders for PVI (28% vs. 11%) and DeltaPP (22% vs. 5%) and both PVIthe higher PVI or DeltaPP is at baseline, the higher the beneficial effect of volume expansion."
Finding that the "performance of PVI to predict fluid responsiveness was similar to that of DeltaPP," researchers concluded that Masimo PVI "can predict fluid responsiveness in intensive care unit patients under mechanical ventilations." Researchers also noted the implications of using such dynamic fluid responsiveness predictors, commenting that "optimizing the patient's hemodynamic state with DeltaPP or PVI monitoring has potential to decrease duration of hospital stay and mechanical ventilation, postoperative morbidity, and costs in patients undergoing high-risk surgery."