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 (∆PPV) at VT₆-₈ (∆PPV₆-₈), VT₈-₁₀ (∆PPV₈-₁₀), VT₆-₁₀ (∆PPV₆-₁₀), and the change in SVV (∆SVV) at VT₆-₈ (∆SVV₆-₈), VT₈-₁₀ (∆SVV₈-₁₀), and VT₆-₁₀ (∆SVV₆-₁₀) 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, ∆PPV and ∆SVV 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 ∆PPV₆-₈, ∆PPV₈-₁₀, and ∆PPV₆-₁₀, and 0.55 (0.30 to 0.80), 0.55 (0.31 to 0.80), and 0.59 (0.34 to 0.84) for ∆SVV₆-₈, ∆SVV₈-₁₀, and ∆SVV₆-₁₀, 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
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