Extravascular Lung Water and Pulmonary Vascular Permeability Index measured at the end of surgery are independent predictors of prolonged mechanical ventilation in patients undergoing liver transplantation.

Abstract

Background: Pulmonary edema (PE) after orthotopic liver transplantation (OLT) may compromise the postoperative course and prolong the duration of mechanical ventilation (MV) and intensive care unit length of stay. Hemodynamic monitoring with transpulmonary thermodilution permits quantification of extravascular lung water index (ELWI) and calculation of the pulmonary vascular permeability index (PVPI), which is the ratio between the ELWI and the pulmonary blood volume. This ratio can discriminate between PE hydrostatic and nonhydrostatic PE. We investigated the relationship between ELWI and PVPI values, measured at the end of surgery, and prolonged MV (PMV) in patients after OLT.

Methods: We retrospectively studied 93 consecutive patients who underwent OLT. We recorded preoperative data including spirometry, echocardiography, severity liver disease with the Model for End-Stage Liver Disease score, and the Child-Pugh classification scores. Intraoperatively, we performed hemodynamic measurements with transpulmonary thermodilution and pulmonary arterial catheters after the induction of anesthesia, 10 minutes before reperfusion, and at the end of surgery. Moreover, we recorded the length of surgery, the amount of IV volume infused, the results of blood coagulation analyses, and blood transfusion. Postoperatively, we recorded the duration of MV and intensive care unit length of stay, mortality, and graft function. Patients were then classified as requiring PMV (>48 hours after surgery) or not. Statistical analyses, preoperative and intraoperative variables between patients with and without PMV, were compared using Mann-Whitney U tests. Receiver-operating characteristic curves were used to evaluate the ability of preoperative and intraoperative variables to predict PMV.

Results: Twelve patients required PMV after surgery. Patients who required PMV exhibited increased ELWI (11.6 ± 3 mL/kg vs 9.3 ± 2 mL/kg, P = 0.0099) and PVPI values (2.94 ± 1 vs 1.8 ± 0.6, P = 0.000015) at the end of surgery. The areas under the receiver-operating characteristic curve were 0.890 ± 0.04 for PVPI with a 99% confidence interval of 0.782 to 0.958 and 0.730 ± 0.08 for ELWI with a 99% confidence interval of 0.594 to 0.839. Using a cutoff of 2.3 for PVPI allowed a sensitivity = 91.7%, a specificity = 83.8, a positive predictive value = 45.8%, and a negative predictive value = 98.5% for predicting PMV. A cutoff of 12 for ELWI allowed a sensitivity of 50%, specificity of 85%, positive predictive value of 33.3%, and negative predictive value of 91.9% for PMV.

Conclusions: PVPI and ELWI values obtained at the end of OLT are useful for predicting the need for postoperative PMV.