Cyanosis

A. False Carboxyhaemoglobin is pink and gives the skin a pinkish colour.

B. True This blue pigment is a rare cause of central cyanosis.

C. False The fingers are red; cold inhibits oxygen dissociation and reduces metabolism.

D. False Cyanosis occurs when arterial blood contains more than 5 g/dl reduced haemoglobin; low haemoglobin values in anaemia make it difficult to reach this level.

E. False Cyanide poisons the enzymes involved in O2 uptake by the tissues; in cyanide poisoning the blood remains fully oxygenated and the skin is pink.