Objective To evaluate the influence of tidal volume on the accuracy of stroke volume variation ( SVV) to predict volume state of pigs with ventilation.Methods Thirty-six healthy pigs were anesthetized after tracheal intubation and ventilated. With the envelope method, they were randomized into a normovolemia group, a hemaerrhagic shock group, and a hypervolemia group, with 12 pigs in each group. The pigs in the hemaerrhagic shock group were removed 20 percent of blood, and the pigs in the hypervolemia group received additional infusion of 20 percent 6% hydroxyethyl starch. In each group, ventilator settings were changed in a randomized order by changing VT [ VT = 5 mL/kg ( VT5 ) , VT =10 mL/kg ( VT10 ) , and VT =15 mL/kg ( VT15 ) ] . Hemodynamic measurements [ heart rate ( HR) , mean arterial boold pressure ( MAP) , systemic vascular resistance index ( SVRI) , cardiac index ( CI) , stroke volume index ( SVI) , intrathoracic blood volume index( ITBVI) , and SVV] were obtained after 10 minutes of stabilization. Results SVV was increased in the hemaerrhagic shock group comparing with the normovolemia group for VT10 [ ( 21 ±5) % vs. ( 11 ±2) % , P lt;0. 05] , but SVV was decreased in the hypervolemia group comparing with the normovolemia group [ ( 7 ±2) % vs. ( 11 ±2) % , P lt; 0. 05] . The variation tendency for VT15 was the same with VT10 , moreover SVV were all above 12% for the hemaerrhagic shock group, the normovolemia group, and the hypervolemia group [ ( 30 ±7) % , ( 19 ±3) % , and ( 15 ±4) % ] . There were no significant diffrences among the hemaerrhagic shock group, hypervolemia group and normovolemia group [ ( 8 ±6) % ,( 7 ±5) % , and ( 7 ±4) % , P gt; 0. 05] for VT5 . Conclusions SVV was a precise indicator of cardiac preload, but SVV was less sensitive to the changes of volume during low tidal volume ( 5 mL/kg) ventilation. The threshold of SVV for predicting fluid responsiveness maybe above 12% with a high tidal volume ( 15 mL/kg) ventilation.
ObjectiveTo evaluate the value of stroke volume variation (SVV) and intrathoracic blood volume index (ITBVI) to predict fluid responsiveness in mechanically ventilated septic shock patients with spontaneous breathing. MethodsA prospective observational study was conducted in the Department of Critical Care Medicine of the First Affiliated Hospital of Guangzhou Medical University. Fluid resuscitation data was collected in septic shock patients who received PiCCO monitoring from June 2013 to June 2014. Transpulmonary thermodilution data were collected before and after fluid resuscitation, including cardiac index (CI), SVV, ITBVI, and central venous pressure (CVP). Seventeen patients were defined as responders by an observed increase of≥15% in the cardiac index (CI) after fluid resuscitation, 12 patients were defined as non-responders. Pearson correlation between changes of CI (ΔCI) and SVV, ITBVI, CVP was established. Area under the receiver operating characteristic (ROC) curve of SVV, ITBVI and CVP was calculated for predicting fluid responsiveness. ResultsBaseline CI and ITBVI were significantly lower in the responders (P < 0.05).There was no significant difference in baseline SVV between the responders and the non-responders (P > 0.05). A significant correlation was found between baseline ITBVI andΔCI (r=-0.593, P < 0.001), but no significant correlation between SVV andΔCI (r=0.037, P=0.847) or CVP andΔCI (r=0.198, P=0.302). The area under ROC curve of SVV, ITBVI and SVV for predicting fluid responsiveness was 0.640 (P=0.207), 0.865 (P=0.001), and 0.463 (P=0.565), respectively. The cut-off value of ITBVI for predicting fluid responsiveness was 784 mL/m2 with a sensitivity of 100.0% and a specificity of 70.6%. ConclusionIn mechanically ventilated septic shock patients with spontaneous breathing, ITBVI may be a valuable indicator in predicting fluid responsiveness compared with SVV.