Background: Lung protective ventilation with low tidal volume (VT) is beneficial in patients with intermediate to high risk of post-operative pulmonary complications. However, during low VT ventilation, pulse pressure variation (PPV) and stroke volume variation (SVV) do not predict fluid responsiveness.

Objective: To determine whether changes in PPV and SVV after transient increases in VT could predict fluid responsiveness.

Materials and Methods: The authors recorded 20 measurements from 15 patients experiencing post-operative acute circulatory failure. The authors performed a VT challenge by transient increasing VT from 6 to 8 mL/kg (VT₆-₈), 8 to 10 mL/kg (VT₈-₁₀), and 6 to 10 mL/kg (VT₆-₁₀) of patients’ predicted body weight. The change in PPV (ΔPPV) at VT₆-₈ (ΔPPV₆-₈), VT₈-₁₀ (ΔPPV₈-₁₀), VT₆-₁₀ (ΔPPV₆-₁₀), and the change in SVV (ΔSVV) at VT₆-₈ (ΔSVV₆-₈), VT₈-₁₀ (ΔSVV₈-₁₀), and VT₆-₁₀ (ΔSVV₆-₁₀) were recorded. Patients were classified as fluid responders if there was an increase in stroke volume of more than 10% after a fluid bolus.

Results: Following the VT challenge, ΔPPV and ΔSVV failed to predict fluid responsiveness, with areas under the receiver operating characteristic curves (with 95% confidence intervals) of 0.49 (0.23 to 0.74), 0.54 (0.29 to 0.79), 0.52 (0.28 to 0.77) for ΔPPV₆-₈, ΔPPV₈-₁₀, and ΔPPV₆-₁₀, and 0.55 (0.30 to 0.80), 0.55 (0.31 to 0.80), and 0.59 (0.34 to 0.84) for ΔSVV₆-₈, ΔSVV₈-₁₀, and ΔSVV₆-₁₀, respectively.

Conclusion: Changes in PPV and SVV after the VT challenge did not predict fluid responsiveness in post-operative patients with low VT ventilation.

Trial registration: Thai Clinical Trials Registry, TCTR 20190808003

Keywords: Pulse pressure variation, Stroke volume variation, Fluid responsiveness, Tidal volume challenge

DOI: doi.org/10.35755/jmedassocthai.2020.08.10697

Received 27 Jan 2020 | Revised 8 May 2020 | Accepted 9 May 2020