Abstract
Introduction: Excessive fluid administration in septic shock worsens clinical outcomes. Pulse pressure variation (PPV) is a validated predictor of fluid responsiveness but requires invasive monitoring, which is not always available.
Objective: To evaluate the diagnostic accuracy of respiratory variations in carotid peak systolic velocity (ΔCPSV) and carotid velocity-time integral (ΔCVTI), and to compare them with PPV in mechanically ventilated patients with septic shock receiving vasopressor support.
Patients and Methods: In this prospective single-center cohort study (n=120), Doppler ultrasonography of the right common carotid artery was used to assess ΔCPSV and ΔCVTI, alongside PPV measurement. Fluid responsiveness was defined by a passive leg raising-induced cardiac output increase ≥12% measured by echocardiography. Diagnostic performance was assessed using ROC analysis (bootstrap BCa 95% CI), AUCs were compared using the DeLong test, and inter-observer reproducibility was evaluated using intraclass correlation coefficients (ICC) in a subsample of 50 patients.
Results: Seventy-eight patients (65%) were fluid responders, and 42 (35%) were non-responders. PPV showed an AUC of 0.94 (95% CI 0.90-0.98), sensitivity of 85.9%, and specificity of 92.9% at a 12% threshold. ΔCPSV demonstrated an AUC of 0.93 (95% CI 0.88-0.97), sensitivity of 93.6%, and specificity of 81.0% at an 11% threshold. ΔCVTI showed an AUC of 0.90 (95% CI 0.84-0.95), sensitivity of 82.1%, and specificity of 85.7% at a 12% threshold. No statistically significant differences in AUCs were observed between methods according to the DeLong test (p=0.17-0.64). The combined ΔCPSV+ΔCVTI model achieved the highest AUC—0.96 (95% CI 0.93-0.99). Both ultrasound indices strongly correlated with PPV (r=0.71 and r=0.69; p<0.001).
Conclusions: ΔCPSV and ΔCVTI are highly accurate, noninvasive predictors of fluid responsiveness, with diagnostic performance comparable to that of invasive PPV. Their combination showed the highest numerical AUC and may represent a practical noninvasive bedside option when invasive monitoring is delayed, unavailable, or undesirable.