Is the pleth variability index a surrogate for pulse pressure variation in a pediatric population undergoing spine fusion?

Summary Objective: To compare simultaneous measurements of pulse pressure variation (PPV) and pleth variability index (PVI) in patients undergoing spinal fusion. Aims: To determine if PVI can be used as a surrogate for PPV and also the influence of the prone position on these measurements. Background: Spine fusion is an involved surgical procedure requiring attention to fluid administration. Dynamic indices for assessing fluid responsiveness like PPV have proven useful to guide fluid administration. Plethysmographic waveform variation like PVI is an appealing surrogate for measurements like PPV that require invasive arterial pressure measurement. Spine fusion patients are unique and the potential of either PPV or PVI to guide fluid therapy has not been studied. Methods: Patients undergoing spine fusion for scoliosis were studied. In addition to the usual monitors including direct arterial pressure measurement, a multi‐wavelength pulse co‐oximeter was applied to measure PVI. Paired measurements of PPV and PVI were obtained and limits of agreement determined using the method of Bland and Altman. PPV and PVI in prone and supine positions were compared by paired t‐test. Results: The bias between PVI and PPV measurements was −0.56% with 95% limits of agreement of +21.67% to −20.55%. There was no significant difference between the prone and supine measurements at the P = 0.05 level ( Table 1 ). Demographics of subjects and case information. Subjects 5 and 8 were excluded due to lack of data in the supine position Subject Age (years) Wt (kg) ASA Sex Duration (h) EBL (ml) Average TV (ml) Average PIP (cmH2O) IV Fluid (ml) Blood (ml) 001 12 43.7 2 M 5.33 1000 401 19 4000 150 002 17 62.2 1 M 7.63 1250 518 20 4000 275 003 16 50 2 F 6.9 1700 355 19 4500 881 004 16 71.3 2 F 6.67 500 524 18 4500 0 006 17 62.3 2 F 6.15 600 490 17 3500 600 007 18 54 2 M 6.12 600 419 15 4200 0 009 11 52.4 1 F 7.27 300 348 29 3000 0 010 14 24.5 3 F 8.37 600 290 18 3500 380 011 18 72.1 2 M 7.02 400 397 15 3100 0 012 16 64.1 1 M 8.9 850 411 20 3300 120 013 13 39.2 3 F 5.33 1100 261 17 5250 739 014 13 49.6 2 M 8.3 1500 376 17 5000 885 015 14 45.2 2 M 6.43 600 350 18 3200 0 016 11 64.6 2 F 6.48 325 468 18 3000 0 017 18 62.1 2 M 8.37 1400 440 21 4000 0 018 13 44 1 F 11.4 400 297 16 4900 0 019 17 67.7 2 M 7.07 600 472 18 4400 100 020 14 47 2 F 4.53 200 351 18 3400 200 021 15 69.3 2 M 6.28 800 570 17 5000 150 022 18 62.5 1 M 7.82 1100 471 17 3250 1100 023 16 56 2 M 6.48 800 370 19 4000 800 024 14 37.8 3 M 8.62 900 342 17 4000 200 EBL, estimated blood loss; TV, tidal volume; PIP, peak inspiratory pressure. Conclusions: Our data indicate that PVI is not a surrogate for PPV. PVI measurements were not influenced by changing from the supine to prone position and therefore may prove useful for patients undergoing spine surgery.