Acute pulmonary oedema

After reading the article on managing acute pulmonary oedema,¹  I would like to point out the following. Pulmonary embolus causes pulmonary ischaemia not oedema. Nitrates do not cause coronary vasodilatation as they are already maximally dilated by way of autoregulation. Morphine causes coronary vasoconstriction in conscious dogs.²

Robert McRitchie
Flinders Medical Centre, Adelaide 

Megan Purvey and George Allen, the authors of the article, comment:

We have further reviewed the literature and agree that pulmonary embolus does cause regional ischaemia, but it is also listed as a precipitant of acute heart failure in the 2016 European Society of Cardiology Guidelines for the Diagnosis and Treatment of Acute and Chronic Heart Failure.³ Similarly, we were guided by the 2005 version of these guidelines which, when discussing nitrates, stated ‘At low doses they only induce venodilation, but as the dose is gradually increased they cause the arteries, including the coronary arteries, to dilate’.⁴

We appreciate your clarification of morphine-induced coronary vasoconstriction² as a mechanism of why morphine may cause harm if used in acute pulmonary oedema.