Intravenous oxygenation (IVOX) is a new technique for augmentation of gas exchange in patients who require near maximal conventional ventilatory support. Patients who require IVOX are, by definition, critically ill with a high expected mortality. At present, these high risk patients must be transferred to the operating theatre for the IVOX device to be inserted. This report describes the anaesthetic problems associated with nine patients in whom an IVOX device was inserted and removed in our institution. The mortality was six out of nine patients; all deaths occurred with the IVOX device in situ. Three patients died within 6 h of insertion. Four patients were female. The patients' ages ranged from 14 to 76 years. There were few immediate ventilation changes in the first 4 h after IVOX insertion. Inspired oxygenation concentration was reduced in only one patient. Positive end-expiratory pressure was not reduced. Peak inspiratory pressure decreased in four patients. Arterial oxygen tension increased in four patients (range 0.1-2.5 kPa) and decreased in five (range 0.1-3.4 kPa). Arterial carbon dioxide tension increased in one patient (0.3 kPa) and decreased in eight (range 0.1-2.7 kPa). Inotropic support with adrenaline, dobutamine and noradrenaline needed to be initiated or increased in eight patients. Eight patients required 2-4 units of blood to be transfused during IVOX insertion or in the following 2 h. One patient suffered an asystolic cardiac arrest during the operation, but was resuscitated successfully. Three patients survived to have the IVOX removed.(ABSTRACT TRUNCATED AT 250 WORDS)