Shakes is a sign of low blood pressure. Poppers reduce blood pressure when blood vessels dilate. Even worse with viagra etc as these do same. Shakes is a sign the heart is struggling to keep up pressue, so next you might faint or have a heart attack. Its a warning sign not to be ignored.
The headache and optical effects of poppers is also an effect from dilation of the blood vessels, in this case those alongside the optic nerve, as happens when people suffer migraines. In fact what you get is a drug induced migraine.
