William C. Wilson, M.D., MA, Chief Medical Officer at UCI Health, said, “Anesthesiologists and critical care physicians have long recognized the importance of dynamic measures of intravascular volume and fluid responsiveness. Previously this data could only be acquired using an invasive arterial line, and/or additional sophisticated devices. With the Masimo pleth variability index (PVi), one can now obtain this essential data using the pulse oximeter probe and following the continuous readout on the monitor. The PVi technology has undergone rigorous peer-reviewed evaluation, and demonstrated efficacy in determining adequacy of intravascular volume for guiding goal-directed therapy. The recent clearance of the Masimo PVi system will serve as another major breakthrough in promoting patient safety.”
Available alongside Masimo SET pulse oximetry and rainbow Pulse CO-Oximetry on a variety of 2-LED, 4-LED, and 8-LED Masimo sensors, PVi is an index between 0 and 100 that is calculated using a proprietary algorithm based upon the relative variability of the pleth waveform.
Hospital protocols such as Enhanced Recovery After Surgery (ERAS) and Goal-directed Therapy (GDT) recommend fluid management as part of larger initiatives designed to improve patient care and safety. Fluid management protocols look to balance fluids by identifying when patients may be fluid responsive. The utility of PVi as a fluid responsiveness indicator has been demonstrated in more than 100 independent, published studies, including in ERAS and GDT protocols.1 For example:
- ERAS: In a study of 109 patients undergoing colorectal surgery, researchers found that the implementation of an ERAS protocol which included PVi led to substantial reductions in lengths of stay (from a median of 5 days to 3 days), complication rates (from 30.1 percent to 14.7 percent), and costs per patient (from mean cost at 30 days of $20,435 to $13,306 per patient)—in addition to improved patient satisfaction.2
- GDT: In a study of 82 patients undergoing major abdominal surgery, researchers found that GDT with fluid management using PVi reduced the volume of intraoperative fluid infused and reduced intraoperative and postoperative lactate levels.3
In addition, PVi has been used in combination with Masimo’s noninvasive, continuous hemoglobin monitoring technology (SpHb). In a study published last year involving 18,716 surgical patients at a hospital in Limoges, France, researchers investigated the effects of implementing a hospital-wide protocol for fluid management and blood administration using PVi and SpHb. The researchers found that use of an integrated GDT algorithm using both PVi and SpHb led to earlier transfusion and fewer units of blood transfused, as well as a 33 percent lower mortality rate 30 days after surgery and a 29 percent lower mortality rate 90 days after surgery. A year after the study ended, when the hospital did not use PVi and SpHb technology, the mortality rate returned to levels similar to those found before implementation of the GDT protocol.4
Stephen Weston, M.D., Health Sciences Associate Clinical Professor and Medical Director, Operating Room Support Services, Department of Anesthesia and Perioperative Care at the University of California, San Francisco, said, “At UCSF we display PVi on all of our Masimo pulse oximeters. PVi is a great tool for helping to assess the patient’s fluid status. Having a fluid responsiveness monitor incorporated into something as ubiquitous as pulse oximetry allows us to monitor fluid responsiveness universally. I integrate PVi into my routine sweeps of the hemodynamic data in the operating room, and we’ve rolled out this functionality to the intensive care units as well. Without PVi, I feel that I’m flying a little bit blind.”
Joe Kiani, Founder and CEO of Masimo, said, “We are thrilled that at long last we are able to offer clinicians and patients in the U.S. the full benefits of PVi monitoring. Multiple studies have shown how this breakthrough noninvasive indicator of fluid responsiveness can help improve outcomes and reduce costs on mechanically ventilated patients—with no more equipment needed than a software upgrade with most existing Masimo SET and rainbow platforms and the existing Masimo SET sensors that so many top hospitals around the world already use for pulse oximetry.”
The accuracy of PVi in predicting fluid responsiveness is variable and influenced by numerous patient, procedure, and device-related factors. PVi measures the variation in the plethysmography amplitude but does not provide measurements of stroke volume or cardiac output. Fluid management decisions should be based on a complete assessment of the patient’s condition and should not be based solely on PVi.
SpHb is not intended to replace laboratory blood testing. Clinical decisions regarding red blood cell transfusions should be based on the clinician’s judgment considering, among other factors, patient condition, continuous SpHb monitoring, and laboratory diagnostic tests using blood samples.
The GDT and ERAS studies summarized above were conducted on patients undergoing specific types of procedures and following specific fluid management protocols. The results may not be reflective of all cases and the described GDT and ERAS protocols may not be appropriate for all types of patients and procedures.
1 Published clinical studies on PVi, with varying results and outcomes, can be found on our website at http://www.masimo.com/evidence/pulse-oximetry/pvi. Studies include independent and objective studies which are comprised of abstracts presented at scientific meetings and peer-reviewed journal articles.
2 Thiele RH et al. Standardization of care: impact of an enhanced recovery protocol on length of stay, complications, and direct costs after colorectal surgery. J Am Coll Surg. 2015 Apr;220(4):430-43.
3 Forget P et al. Goal-directed fluid management based on the pulse oximeter-derived pleth variability index reduces lactate levels and improves fluid management. Anesth Analg. 2010 Oct;111(4):910-4.
4 Cros J et al. Continuous hemoglobin and plethysmography variability index monitoring can modify blood transfusion practice and is associated with lower mortality. J Clin Monit Comp. 3 Aug 2019. https://doi.org/10.1007/s10877-019-00367-z.