1 rich Libsyn https://www.libsyn.com 90 600 Author: Nick Hatch, M.D. Educational Pearls: &amp;nbsp; Methemoglobinemia is when the iron in hemoglobin is in the Fe3+ (ferric) state rather than the normal Fe2+ &amp;nbsp;(ferrous) state. Methemoglobin cannot release oxygen at the tissues. Symptoms include cyanosis, headache, tachycardia, dyspnea, and lethargy. Suspect in setting of hypoxia that does not improve with oxygenation, and clinical cyanosis with a normal PaO2 on ABG. Treatment is methylene blue which reduces the iron back to the ferrous state. Causes can be Dapsone, Lidocaine, Benzocaine. &amp;nbsp; References: Agarwal N, Nagel RL, Prchal JT. Dyshemoglobinemias. In: Disorders of Hemoglobin: Genetics, Pathophysiology, and Clinical Management, 2nd ed, Steinberg M (Ed), 2009. P.607 Cortazzo JA, Lichtman AD. (2014). Methemoglobinemia: a review and recommendations for management. Journal of Cardiothoracic and Vascular Anesthesia. 28:1043. Darling R, Roughton F. (1942). The effect of methemoglobin on the equilibrium between oxygen and hemoglobin. American Journal of Physiology. 137:56. Emergency Medical Minute https://www.emergencymedicalminute.com <iframe title="Libsyn Player" style="border: none" src="//html5-player.libsyn.com/embed/episode/id/6519629/height/90/theme/custom/thumbnail/yes/direction/forward/render-playlist/no/custom-color/fa102a/" height="90" width="600" scrolling="no" allowfullscreen webkitallowfullscreen mozallowfullscreen oallowfullscreen msallowfullscreen></iframe> https://assets.libsyn.com/secure/content/20606598