Assessment of dynamic left ventricular outflow track obstruction as fluid responsiveness marker in mechanically ventilated septic patients

Abstract

Background: Sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection. Similar to poly trauma, acute myocardial infarction, or stroke, early identification and appropriate management in the initial hours after sepsis develops improves outcomes. In a patient with septic shock, a fluid challenge will cause an increase in stroke volume; according to the Frank-Starling curve [1] .Relative hypovolemia has been described in the setting of septic shock. However, only 50 % of patients with hemodynamic instability are fluid responsive [2] . Purpose: Assessment of Fluid responsiveness in ventilated septic shock patients according to presence of LVOT obstruction and to judge the power of prediction of other hemodynamic parameters. Methods: A prospective observational study was carried out on 50 adult mechanically ventilated patients with septic shock. Two sets of measurements were performed before and immediately after volume expansion. Cardiac output (CO), stroke volume (SV), IVC distensibility index (dIVC), LVOT velocity ( m/s ,Mean and peak pressure gradient (mmHg) were measured by transthoracic echocardiography. Fluid challenge responders were defined as patients whose cardiac output was increased ≥15 %. The area under the receiver operating characteristic curve (AUC) was compared for each predictive parameter. Results:During the study period, LVOT obstruction was found in 18 patients (36 %). Mortality rate at 60 days was found to be higher in patients with LVOT than in patients without LVOT obstruction (75% versus 25%, p < 0.01). Around 90 % of patients with LVOT obstruction were fluid responders versus 60 % from patient without LVOT obstruction (P-value=0.04). IVC distensibility index predicts fluid responsiveness at a cutoff point 17% with a sensitivity 88% and specificity 83 %( pvalue < 0.001 and AUC= 0.934) Conclusions: LVOT obstruction in the early phase of septic shock is not rare (more than one third of septic shock patients) and is associated with a high mortality rate.Patients who have LVOT, are more fluid responsive than whom have no LVOT. IVC distensibility index carries important baseline parameters that could predict fluid responsiveness in mechanically ventilated patients with septic shock