Understanding GTN and shunting

[mona4522]

I work in ICU and we have numerous patients on GTN infusions, frequently on very high doses. We notice that sometimes once the GTN has been commenced the patients oxygenation drops, senior staff refer to this as "shunting". Can anyone explain what they mean by this?

[ghillbert, MSN, NP]

Nitroglycerin (NTG/GTN) causes vessel dilation by increasing nitric oxide at vascular level. In patients with lung disease, you increase blood flow to non-oxygenated areas and thus you get a drop in O2 sat - this is called "intrapulmonary shunting".