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We analyzed the tissue oxygen extraction in 25 patients with acute respiratory failure. Fourteen met the clinical criteria for the adult respiratory distress syndrome (ARDS). The 11 remaining patients had acute respiratory failure with causes different from ARDS. In all cases the changes in the oxygen extraction ratio (O2ER) and in the oxygen consumption (VO2) were evaluated after changing oxygen availability (O2A) with positive end-expiratory pressure (PEEP) and dobutamine infusion. The patients with ARDS showed a change in VO2 parallel to O2A changes, with a significant correlation (r = 0.85); however, no changes were found in O2ER (r = 18). In the patients without ARDS, the changes in O2A did not modify the VO2 (r = 0.02) but there was a significant inverse relationship between DO2 and O2ER (r = -0.70). These findings suggest an abnormal regulation of tissue oxygen extraction and an abnormal dependence of VO2 on O2A in cases with ARDS. Dobutamine therapy, in addition to inotropic effects, could improve a situation of hidden hypoxia, as it is a vasodilator that might act on microvasculature.

Cytology in blood drawn through a wedged Swan-Ganz catheter appears as a sensitive method for the diagnosis of carcinomatous lymphangitis in patients in whom transbronchial biopsy is considered dangerous or who refuse to undergo the latter procedure. However, its usefulness has not been assessed in critical patients with acute respiratory failure of unknown etiology in whom malignant disease is suspected. We report our experience in two patients admitted to the Intensive Care Unit with acute respiratory failure of unknown etiology: they were a female with breast carcinoma and a male with lymphoma in whom the cytological study of pulmonary capillary blood disclosed malignant cells. The clinical evaluation and the subsequent histological studies confirmed the pulmonary involvement by malignant disease in both cases.

A case is presented of minimum renal trauma, leading to a retroperitoneal hematoma as a consequence of a simple renal cyst rupture as well as an artery contained therein. The etiopathogenicity of this phenomenon is commented. The different clinical manifestations of renal trauma are highlighted, as well as the suspicion of previous renal pathology when a large renal lesion is found secondary to minimum renal trauma. The approach of the renal pediculum must be the first step in the surgical treatment of renal trauma.