Efficacy of using tidal volume challenge to improve the reliability of pulse pressure variation reduced in low tidal volume ventilated critically ill patients with decreased respiratory system compliance

Assessment of fluid responsiveness after tidal volume challenge in renal transplant recipients: a nonrandomized prospective interventional study

Background

When applying lung-protective ventilation, fluid responsiveness cannot be predicted by pulse pressure variation (PPV) or stroke volume variation (SVV). Functional hemodynamic testing may help address this limitation. This study examined whether changes in dynamic indices such as PPV and SVV, induced by tidal volume challenge (TVC), can reliably predict fluid responsiveness in patients undergoing renal transplantation who receive lung-protective ventilation.

Methods

This nonrandomized interventional study included renal transplant recipients with end-stage renal disease. Patients received ventilation with a 6 mL/kg tidal volume (TV), and the FloTrac system was attached for continuous hemodynamic monitoring. Participants were classified as responders or nonresponders based on whether fluid challenge increased the stroke volume index by more than 10%.

Results

The analysis included 36 patients, of whom 19 (52.8%) were responders and 17 (47.2%) were nonresponders. Among responders, the mean ΔPPV6-8 (calculated as PPV at a TV of 8 mL/kg predicted body weight [PBW] minus that at 6 mL/kg PBW) was 3.32±0.75 and ΔSVV6-8 was 2.58±0.77, compared to 0.82±0.53 and 0.70±0.92 for nonresponders, respectively. ΔPPV6-8 exhibited an area under the curve (AUC) of 0.97 (95% confidence interval [CI], 0.93-1.00; P≤0.001), with an optimal cutoff value of 1.5, sensitivity of 94.7%, and specificity of 94.1%. ΔSVV6-8 displayed an AUC of 0.93 (95% CI, 0.84-1.00; P≤0.001) at the same cutoff value of 1.5, with a sensitivity of 94.7% and a specificity of 76.5%.

Conclusions

TVC-induced changes in PPV and SVV are predictive of fluid responsiveness in renal transplant recipients who receive intraoperative lung-protective ventilation.

Effect of different targets of goal-directed fluid therapy on intraoperative hypotension and fluid infusion in robot-assisted laparoscopic gynecological surgery: a randomized non-inferiority trial

Carotid corrected flow time (FTc) and tidal volume challenge pulse pressure variation (VtPPV) are useful clinical parameters for assessing volume status and fluid responsiveness in robot-assisted surgery, but their usefulness as goal-directed fluid therapy (GDFT) targets is unclear. We investigated whether FTc or VtPPV as targets are inferior to PPV in GDFT. This single-center, prospective, randomized, non-inferiority study included 133 women undergoing robot-assisted laparoscopic gynecological surgery in the modified head-down lithotomy position. Patients were equally divided into three groups, and the GDFT protocol was guided by FTc, VtPPV, or PPV during surgery. Primary outcomes were non-inferiority of the time-weighted average of hypotension, intraoperative fluid volume, and urine output. Secondary outcomes were optic nerve sheath diameter (ONSD) pre- and post-operatively and creatinine and blood urea nitrogen preoperatively and on day 1 post-operatively. No significant differences were observed in intraoperative hypotension index, infusion and urine volumes, and ONSD post-operatively between the FTc and VtPPV groups and the PPV group. No differences in serum creatinine and urea nitrogen levels were identified between the FTc and VtPPV groups preoperatively, but on day 1 post-operatively, the urea nitrogen level in the FTc group was higher than that in the PPV group (4.09 ± 1.28 vs. 3.0 ± 1.1 mmol/L, 1.08 [0.59, 1.58], p < 0.0001), and the difference from the preoperative value was smaller than that in the PPV group (- 2 [- 2.97, 1.43] vs. - 1.34 [- 1.9, - 0.67], p = 0.004). FTc- or VtPPV-guided protocols are not inferior to that of PPV in GDFT during robot-assisted laparoscopic surgery in the modified head-down lithotomy position.Trial registration: Chinese Clinical Trial Registry (ChiCTR2200064419).

Superior vena cava collapsibility index as a predictor of fluid responsiveness: a systematic review with meta-analysis

INTRODUCTION

The superior vena cava collapsibility index (SVC-CI) is a potential marker of fluid responsiveness (FR) in mechanically ventilated patients. Few studies reporting its diagnostic performance are currently available.

MATERIAL AND METHODS

A systematic search, using the PRISMA approach, was performed using the Medline and EMBASE databases. Prospective studies evaluating the SVC-CI as a marker of FR in ventilated adult patients were included. A bivariate random-effect model was utilised to generate the summary receiver operating characteristic (SROC) curve. The area under the ROC curve (AUC), the sensitivity and specificity of the curve operating point were calculated.

RESULTS

We included eight studies with a total of 857 patients, in whom SVC-CI was evaluated a total of 1083 times prior to the volume expansion trial. In 609 (56.23%) trial cases FR was present. The SROC curve demonstrated that the test's operating point has a sensitivity and specificity of 80.8% (95% CI: 66.3-90%) and 81.4% (95% CI: 76.4-85.5%), respectively. The model's AUC was equal to 0.848 (95% CI: 0.824-0.863) with P < 0.001. No significant inter-study heterogeneity was found (I 2 = 0%). A subgroup analysis revealed a significantly lower sensitivity of SVC-CI in patients with higher levels of positive end-expiratory pressure (PEEP) (> 5 cm H 2 O) (χ 2 = 7.753, df = 2, P = 0.0207). The study setting and type of intervention for volume expansion did not significantly change the performance of the test.

CONCLUSIONS

SVC-CI is a reliable predictor of FR for mechanically ventilated patients in intensive care units and operating rooms. A PEEP level exceeding 5 cm H 2 O may impair the sensitivity of the test.

Does tidal volume challenge improve the feasibility of pulse pressure variation in patients mechanically ventilated at low tidal volumes? A systematic review and meta-analysis

BACKGROUND

Pulse pressure variation (PPV) has been widely used in hemodynamic assessment. Nevertheless, PPV is limited in low tidal volume ventilation. We conducted this systematic review and meta-analysis to evaluate whether the tidal volume challenge (TVC) could improve the feasibility of PPV in patients ventilated at low tidal volumes.

METHODS

PubMed, Embase and Cochrane Library inception to October 2022 were screened for diagnostic researches relevant to the predictability of PPV change after TVC in low tidal volume ventilatory patients. Summary receiving operating characteristic curve (SROC), pooled sensitivity and specificity were calculated. Subgroup analyses were conducted for possible influential factors of TVC.

RESULTS

Ten studies with a total of 429 patients and 457 measurements were included for analysis. The predictive performance of PPV was significantly lower than PPV change after TVC in low tidal volume, with mean area under the receiving operating characteristic curve (AUROC) of 0.69 ± 0.13 versus 0.89 ± 0.10. The SROC of PPV change yielded an area under the curve of 0.96 (95% CI 0.94, 0.97), with overall pooled sensitivity and specificity of 0.92 (95% CI 0.83, 0.96) and 0.88 (95% CI 0.76, 0.94). Mean and median cutoff value of the absolute change of PPV (△PPV) were 2.4% and 2%, and that of the percentage change of PPV (△PPV%) were 25% and 22.5%. SROC of PPV change in ICU group, supine or semi-recumbent position group, lung compliance less than 30 cm H₂O group, moderate positive end-expiratory pressure (PEEP) group and measurements devices without transpulmonary thermodilution group yielded 0.95 (95%0.93, 0.97), 0.95 (95% CI 0.92, 0.96), 0.96 (95% CI 0.94, 0.97), 0.95 (95% CI 0.93, 0.97) and 0.94 (95% CI 0.92, 0.96) separately. The lowest AUROCs of PPV change were 0.59 (95% CI 0.31, 0.88) in prone position and 0.73 (95% CI 0.60, 0.84) in patients with spontaneous breathing activity.

CONCLUSIONS

TVC is capable to help PPV overcome limitations in low tidal volume ventilation, wherever in ICU or surgery. The accuracy of TVC is not influenced by reduced lung compliance, moderate PEEP and measurement tools, but TVC should be cautious applied in prone position and patients with spontaneous breathing activity. Trial registration PROSPERO (CRD42022368496). Registered on 30 October 2022.