There's an interesting case study in the Journal of Veterinary Internal Medicine about a dog (juvenile, mixed breed) who presented with cyanosis, tachycardia, tachypnea, lethargy, exercise intolerance, and aggression when touched on the head.
There's a lot going on there. To cut to the chase, a methylene blue IV administration (1 mg/kg) took care of the problem, which turned out to be a pair of gene mutations that led to reductase deficiency and then methemoglobinemia.
The symptoms returned after 11 days, but a slightly higher dose of the methylene blue fixed the issue and now Fido (not his real name) gets that higher concentration every other day which keeps his methemoglobin concentration at bay.
Methemoglobinemia can affect different animals differently, and while the solution seems straightforward — methylene blue — it's obviously critical to choose the right concentration and possibly
