Objective: To compare the single thermodilution and the thermal-dye dilution techniques with postmortem gravimetry for assessment of changes in extravascular lung water after pneumonectomy and to explore the evolution of edema after injurious ventilation of the left lung.
Design: Experimental study.
Setting: University laboratory.
Subjects: A total of 30 sheep weighing 35.6 ± 4.6 kg. The study included two parts: a pneumonectomy study (n = 18) and an injurious ventilation study (n = 12).
Methods: Sheep were anesthetized and mechanically ventilated with an Fio2 of 0.5, tidal volume of 6 mL/kg, and positive end-expiratory pressure of 2 cm H2O. In the pneumonectomy study, sheep were assigned to right-sided pneumonectomy (n = 7), left-sided pneumonectomy (n = 7), or lateral thoracotomy only (sham operation, n = 4). In the injurious ventilation study, right-sided pneumonectomy was followed by ventilation with a tidal volume of 12 mL/kg and positive end-expiratory pressure of 0 cm H2O (n = 6) or by ventilation with a tidal volume of 6 mL/kg and positive end-expiratory pressure of 2 cm H2O for 4 hrs (n = 6). Volumetric variables, including extravascular lung water index (EVLWI), were measured with single thermodilution (STD; EVLWISTD) and thermal-dye dilution (TDD; EVLWITDD) techniques. We monitored pulmonary hemodynamics and respiratory variables. After the sheep were killed, EVLWI was determined for each lung by gravimetry (EVLWIG).
Results: In total, the study yielded strong correlations of EVLWISTD and EVLWITDD with EVLWIG (n = 30; r = .83 and .94, respectively; p < .0001). After pneumonectomy, both the left- and the right-sided pneumonectomy groups displayed significant decreases in EVLWISTD and EVLWITDD. The injuriously ventilated sheep demonstrated significant increases in EVLWI that were detected by both techniques. The mean biases (±2 sd) compared with EVLWIG were 3.0 ± 2.6 mL/kg for EVLWISTD and 0.4 ± 1.6 mL/kg for EVLWITDD.
Conclusions: After pneumonectomy and injurious ventilation of the left lung, TDD and STD displayed changes in extravascular lung water with acceptable accuracy when compared with postmortem gravimetry. Ventilator-induced lung injury seems to be a crucial mechanism of pulmonary edema after pneumonectomy.
From the Department of Anesthesiology, Institute of Clinical Medicine, University of Tromsø, Tromsø, Norway (VVK, EVS, MYK, VNK, MS, SJ, KW, LJB); and the Department of Anesthesiology and Intensive Care Medicine, Northern State Medical University, Arkhangelsk, Russian Federation (VVK, EVS, MYK).
Presented, in part, at the 28th Scandinavian Congress of Anesthesiologists, Reykjavik, Iceland, July 2005; at the Norwegian Anesthesiological Society, Tromsø, Norway, October 2005; and at the Euroanesthesia Congress 2006, Madrid, Spain, June 2006.
Dr. Kirov is a member of the medical advisory board of Pulsion Medical Systems. The other authors have not disclosed any potential conflicts of interest.
Supported, in part, by Helse Nord, Norway (project 4001.721.477); the Research Council of Norway; Pulsion Medical Systems, Germany; and departmental funds of the Department of Anesthesiology, University Hospital of North Norway.
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