<prompt> Concentration of methemoglobin to appears cyanosis: PGI June 20075 gmdi2gmdf1.5gmdl12 gmdi  <response>: Ans. C 1.5 gdl An methemoglobin level of 15 i.e. 1.5 gdl Q is associated with visible cyanosisQ; a level of 70 MHg level is fatal- Nelson 18th2033MethemoglobinemiaQ is a condition in which the iron within hemoglobin is oxidized from the ferrous Fe2 state to the ferric Fe3 state, resulting in the inability to transport oxygen and carbon dioxide. Clinically, this condition causes cyanosis.Methemoglobinemia in children usually results from exposure to : Oxidizing substances nitrates or nitrites, aniline dyes, or medications, indications, including lidocaine, prilocaine, and phenazopyridine hydrochloride.Cyanosis Occurs WhenDeoxygenated hemoglobin usually in amounts 4 gdL orMethemoglobin 1.5 gdL Q orSulfhemoglobin 0.5 gdLQ CYANOSIS Centralcyanosis Peripheralcyanosis Central cyanosis is caused by in adequate oxygenation of systemic arterial blood due to decreased arterial oxygenQ saturation or Hemoglobin abnormalities It results from cardiac shunting, pulmonary diseases or hematological disorders Hb abnormalities Central cyanosis is charachterized by cyanosis affective both mucous membranes and skin5 Peripheral cyanosis is caused by slowing of blood flow and increased extraction of oxygen from normally saturated blood It results from vasoconstriction or decreased peripheral blood flow, reduced cardiac output or vascular occlusion Peripheral cyanosis is characterized by cyanosis of skin alone and sparing of mucous membranes3 