• M Wenz, B Hoffmann, J Bohlender, and G Kaczmarczyk.
• Clinic of Anesthesiology and Operative Intensive Medicine, Universitätsklinikum Charité Campus Virchow-Klinikum, Berlin, Germany.
• Intensive Care Med. 2000 Mar 1; 26 (3): 292-8.

ObjectiveIn patients with acute respiratory distress syndrome (ARDS), the prone position may enhance oxygenation by changing ventilation/perfusion ratio. In this study, we investigated whether the prone position affects the net balance between pulmonary endothelin (ET-1) and angiotensin II (Ang II) production and clearance, two metabolic functions of lung endothelial cells.SettingAnaesthesiological intensive care unit of a university hospital.PatientsTen ARDS patients (Murray score > 2.5) were studied in both the supine position (SP) and the prone position (PP). MEASUREMENTS AND DESIGN: Blood samples were taken simultaneously from the patient in SP for assessment of mixed venous and arterial ET-1 and Ang II concentrations, and plasma renin concentration (PRC). This was repeated after 60 min in SP, immediately after turning the patient into PP, and 60 min thereafter. Net arterial/mixed venous ET-1 clearances and net Ang II formations were calculated.Resultsarterial oxygen tension increased from SP to PP by an average of 60 mmHg, about 20%. Arterial ET-1 concentrations of ARDS patients were 1.57 +/- 1.1 pg/ml (mean +/- SD) and within the range of healthy persons. Net ET-1 clearances were negative in SP, indicating pulmonary release of ET-1, and did not change in PP. Arterial Ang II concentrations (73 +/- 56 pg/ml) as well as PRC (126 +/- 85 pg/ml) were markedly elevated. Net transpulmonary Ang II formation did not change.ConclusionAcute changes of oxygenation in ARDS patients by positioning do not induce any short-term effects on pulmonary ET-1 net clearance or Ang II net formation.

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