Comparison between conventional pleth variability index (PVI) and Rainbow PVI (RPVI) in non-cardiothoracic surgery: a retrospective study.

BACKGROUND

The rainbow pleth variability index (RPVI) is a newly introduced multiwavelength variant of the pleth variability index (PVI). However, the clinical data on RPVI remains limited. This study retrospectively compared PVI and RPVI in non-cardiothoracic surgery patients using pulse pressure variation (PPV) as a reference.

METHODS

Adult patients (≥20 years) who underwent non-cardiothoracic surgery under general anesthesia and had concurrent RPVI, PVI, and invasive arterial pressure monitoring were included. Repeated-measures correlation was used to evaluate the association with PPV. Agreement was assessed using nested Bland-Altman analysis, and receiver operating characteristic (ROC) curve analysis was conducted to assess the predictive performance for detecting high PPV (>13%).

RESULTS

A total of 86 cases (195.3 h of data) were analyzed. The RPVI showed a stronger correlation with PPV than with PVI (r = 0.511 vs. r = 0.243). The Bland-Altman analysis revealed narrower limits of agreement for the RPVI, indicating greater precision. RPVI also demonstrated better predictive performance, with an area under the curve of 0.813 (95% CI, 0.804-0.821) compared to 0.663 (95% CI, 0.653-0.674) for PVI (P < 0.001). The optimal thresholds for detecting PPV >13% were 8.5 for RPVI and 13.5 for PVI.

CONCLUSIONS

RPVI demonstrated superior performance compared with PVI, showing a stronger correlation and greater precision with respect to PPV, as well as an improved ability to detect states of elevated PPV. While not a direct substitute for PPV, RPVI may serve as a promising non-invasive index for fluid status assessment.