An assessment of global end-diastolic volume and extravascular lung water index during one-lung ventilation: is transpulmonary thermodilution usable?

Abstract

The thermodilution curve assessed by transpulmonary thermodilution is the basis for calculation of global end-diastolic volume index (GEDI) and extravascular lung water index (EVLWI). Until now, it was unclear whether the method is affected by 1-lung ventilation. Therefore, aim of our study was to evaluate the impact of 1-lung ventilation on the thermodilution curve and assessment of GEDI and EVLWI. In 23 pigs, mean transit time, down slope time, and difference in blood temperature (ΔTb) were assessed by transpulmonary thermodilution. "Gold standard" cardiac output was measured by pulmonary artery flowprobe (PAFP) and used for GEDIPAFP and EVLWIPAFP calculations. Measurements were performed during normovolemia during double-lung ventilation (M1), 15 minutes after 1-lung ventilation (M2) and during hypovolemia (blood withdrawal 20 mL/kg) during double-lung ventilation (M3) and again 15 minutes after 1-lung ventilation (M4). Configuration of the thermodilution curve was significantly affected by 1-lung ventilation demonstrated by an increase in ΔTb and a decrease in mean transit time and down slope time (all P < 0.04) during normovolemia and hypovolemia. GEDIPAFP was lower after 1-lung ventilation during normovolemia (M1: 459.9 ± 67.5 mL/m(2); M2: 397.0 ± 54.8 mL/m(2); P = 0.001) and hypovolemia (M3: 300.6 ± 40.9 mL/m(2); M4: 275.2 ± 37.6 mL/m(2); P = 0.03). EVLWIPAFP also decreased after 1-lung ventilation in normovolemia (M1: 9.0 [7.3, 10.1] mL/kg; M2: 7.4 [5.8, 8.3] mL/kg; P = 0.01) and hypovolemia (M3: 7.4 [6.3, 9.7] mL/kg; M4: 5.8 [5.2, 7.4]) mL/kg; P = 0.0009). Configuration of the thermodilution curve and therefore assessment of GEDI and EVLWI are significantly affected by 1-lung ventilation.