Morphine in the treatment of acute pulmonary oedema--Why?

Morphine has for a long time, been used in patients with acute pulmonary oedema due to its anticipated anxiolytic and vasodilatory properties, however a discussion about the benefits and risks has been raised recently. A literature search in Medline and Embase using the keywords "pulmonary oedema" OR "lung oedema" OR "acute heart failure" AND "morphine" was performed. A certain vasodilation has been described after morphine administration, but the evidence for this mechanism is relatively poor and morphine-induced anxiolysis may possibly be the most important factor of morphine in pulmonary oedema and therefore some authors have suggested benzodiazepines as an alternative treatment. Respiratory depression seems to be a less relevant clinical problem according to the literature, whereas vomiting is common, which may cause aspiration. In the largest outcome study, based on the ADHERE registry, morphine given in acute decompensated heart failure was an independent predictor of increased hospital mortality, with an odds ratio of 4.8 (95% CI: 4.52-5.18, p<0.001). Other, smaller studies have shown a significant association between morphine administration and mortality, which was lost after adjusting for confounding factors. Morphine is still used for pulmonary oedema in spite of poor scientific background data. A randomised, controlled study is necessary in order to determine the effect--and especially the risk--when using morphine for pulmonary oedema. Since the positive effects are not sufficiently documented, and since the risk for increased mortality cannot be ruled out, one can advocate that the use should be avoided.