Cyanosis is caused by:
Cyanosis or blue discoloration of mucous membrane is an index of hypoxia or decreased oxygen at the tissue level. It may occur in stagnant hypoxia, hypoxic hypoxia methemoglobinemia maybe treated by reducing Fe by methylene blue. Severe anemic hypoxia <5 gm% can never result in cyanosis (reduced Hb >5 gm%)
Reduced Hb above 7.5 g/dl
Met hb above 1.5 g/dl
Sulph. Hb above 0.5 g/dl
All of the above