Paradoxical increase of pulmonary vascular resistance during testing of inhaled iloprost.

The case of a 14 month old girl with primary pulmonary hypertension treated with domiciliary oxygen is described. After invasive evaluation and testing of nitric oxide with very good response, the testing was repeated to study the effect of inhaled iloprost on pulmonary vascular resistance (PVR). An unexpected and severe increase of PVR was observed, rising from 392 dynes x s x cm(-5) with oxygen to a maximum of 1192 dynes x s x cm(-5) with oxygen and iloprost. Underlying ventilatory and technical problems were excluded. While inhaled iloprost has been described to be highly effective in the treatment of primary pulmonary hypertension, the possibility of contrary "paradoxical" reactions in isolated patients is emphasised, with a dramatic increase of PVR and a possible adverse outcome.