Pleth variability index may predict preload responsiveness in patients treated with nasal high flow: a physiological study

The purpose of this study was to determine whether the plethysmographic variability index (PVi) can predict preload responsiveness in nasal high flow (NHF) patients (≥30 L/min) with any sign of hypoperfusion. Preload responsiveness was defined as a ≥10% increase in stroke volume (SV), measured by transthoracic echocardiography, after passive leg raising. SV and PVi were reassessed in preload responders after receiving a 250-mL fluid challenge. Twenty patients were included, and 12 patients (60%) were preload responders. Responders showed higher baseline mean PVi (24% vs. 13%; p=0.001) and higher mean PVi variation (∆PVi) after passive leg raising (6.8% vs. -1.7%; p<0.001). No differences between mean ∆PVi after passive leg raising and mean ∆PVi after fluid challenge were observed (6.8 % vs. 7.4%; p=0.24), and both values were strongly correlated (r=0.84; p<0.001). Baseline PVi and ∆PVi after passive leg raising showed excellent diagnostic accuracy identifying preload responders (AUROC 0.92 and 1.00, respectively). Baseline PVi ≥16% had a sensitivity of 91.7% and a specificity of 87.5% for detecting preload responders. Similarly, ∆PVi after passive leg raising ≥2%, had a 100% of both sensitivity and specificity. Thus, PVi might predict preload responsiveness in patients treated with NHF, suggesting that it may guide fluid administration in these patients.

Intraoperative Assessment of Fluid Responsiveness in Normotensive Dogs under Isoflurane Anaesthesia

The aim of this study was to evaluate the incidence of fluid responsiveness (FR) to a fluid challenge (FC) in normotensive dogs under anaesthesia. The accuracy of pulse pressure variation (PPV), systolic pressure variation (SPV), stroke volume variation (SVV), and plethysmographic variability index (PVI) for predicting FR was also evaluated. Dogs were anaesthetised with methadone, propofol, and inhaled isoflurane in oxygen, under volume-controlled mechanical ventilation. FC was performed by the administration of 5 mL/kg of Ringer’s lactate within 5 min. Cardiac index (CI; L/min/m2), PPV, (%), SVV (%), SPV (%), and PVI (%) were registered before and after FC. Data were analysed with ANOVA and ROC tests (p < 0.05). Fluid responsiveness was defined as 15% increase in CI. Eighty dogs completed the study. Fifty (62.5%) were responders and 30 (37.5%) were nonresponders. The PPV, PVI, SPV, and SVV cut-off values (AUC, p) for discriminating responders from nonresponders were PPV >13.8% (0.979, <0.001), PVI >14% (0.956, <0.001), SPV >4.1% (0.793, <0.001), and SVV >14.7% (0.729, <0.001), respectively. Up to 62.5% of normotensive dogs under inhalant anaesthesia may be fluid responders. PPV and PVI have better diagnostic accuracy to predict FR, compared to SPV and SVV.

Individualized Fluid Management Using the Pleth Variability Index

Background The present trial was designed to assess whether individualized strategies of fluid administration using a noninvasive plethysmographic variability index could reduce the postoperative hospital length of stay and morbidity after intermediate-risk surgery. Methods This was a multicenter, randomized, nonblinded parallel-group clinical trial conducted in five hospitals. Adult patients in sinus rhythm having elective orthopedic surgery (knee or hip arthroplasty) under general anesthesia were enrolled. Individualized hemodynamic management aimed to achieve a plethysmographic variability index under 13%, and the standard management strategy aimed to maintain a mean arterial pressure above 65 mmHg during general anesthesia. The primary outcome was the postoperative hospital length of stay decided by surgeons blinded to the group allocation of the patient. Results In total, 447 patients were randomized, and 438 were included in the analysis. The mean hospital length of stay ± SD was 6 ± 3 days for the plethysmographic variability index group and 6 ± 3 days for the control group (adjusted difference, 0.0 days; 95% CI, −0.6 to 0.5; P = 0.860); the theoretical postoperative hospital length of stay was 4 ± 2 days for the plethysmographic variability index group and 4 ± 1 days for the control group (P = 0.238). In the plethysmographic variability index and control groups, serious postoperative cardiac complications occurred in 3 of 217 (1%) and 2 of 224 (1%) patients (P = 0.681), acute postoperative renal failure occurred in 9 (4%) and 8 (4%) patients (P = 0.808), the troponin Ic concentration was more than 0.06 μg/l within 5 days postoperatively for 6 (3%) and 5 (2%) patients (P = 0.768), and the postoperative arterial lactate measurements were 1.44 ± 1.01 and 1.43 ± 0.95 mmol/l (P = 0.974), respectively. Conclusions Among intermediate-risk patients having orthopedic surgery with general anesthesia, fluid administration guided by the plethysmographic variability index did not shorten the duration of hospitalization or reduce complications. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New

Plethysmographic variability index as a tool to assess fluid responsiveness in critically ill patients: a correlation study with inferior vena cava distensibility index

Background: In critically ill patients in the intensive care unit (ICU), early aggressive fluid replacement is the cornerstone of resuscitation. Traditionally employed static measures of fluid responsiveness have a poor predictive value. It is therefore imperative to employ dynamic measures of fluid responsiveness that take into account the heart lung interactions in the mechanically ventilated patients. The main objective of this study was to evaluate the reliability of one such non-invasive dynamic index: Plethysmographic variability index (PVI) compared to the widely employed Inferior vena cava distensibility index (dIVC).Methods: Seventy-six adult patients admitted at a tertiary care mixed ICU, who developed hypotension (MAP<65mmHg), were included in the study. PVI was recorded using the MASIMO-7 monitor and dIVC measurements done using Terason ultrasound. Based on the dIVC measurement threshold of 18%, the patients were classified into volume responders and non-responders. The hemodynamic, PVI and dIVC measurements were recorded at pre specified time points following a fluid challenge of 20 ml/kg crystalloid infusion.Results: Baseline PVI values were significantly higher in the responders (22.3±8.2) compared to non-responders (10.1±2.9) (p<0.001) and showed a declining trend at all time points in the responders. Similar declining trend was observed in the dIVC measurements. Overall, the Pearson correlation graph showed strong correlation between dIVC and PVI values at all time points (r=0.678, p=0.001). The ROC curve between the dIVC and PVI values revealed that Baseline PVI (Pre PVI) >15.5% discriminated between responders and non-responders with a 90.2% sensitivity and 75% specificity with an AUC of 0.84 (0.72-0.96) (p<0.001).Conclusions: There is good correlation between PVI values and measured dIVC values at baseline and following a fluid challenge. Thus, PVI may be an acceptable, real time, continuous, surrogate measure of fluid responsiveness in critically ill patients.