Could you comment on the use of nitroglycerin to dilate the veins prior to venipuncture?
—Ana Soto Muniz, MD, Ponce, P.R.
Theoretically, nitroglycerin might help in desperate circumstances, but there are many potential adverse effects. Difficulty with venous access often occurs in the elderly, in the presence of hypotension, or in situations of peripheral vasoconstriction (certain forms of shock, for example). A large enough dose of topical nitroglycerin might exacerbate the hypotension, worsen a number of the aforementioned circumstances, or predispose an elderly person to orthostasis (albeit temporarily).
—Christopher Ruser, MD (116-3)