Nonimmune Hemolytic Anemia Most etiologies of nonimmune hemolytic anemia require observation and supportive care, including removal of the offending agent and prevention of renal damage due to significant hemolysis (see Table 93.3 ) Infectious agents that may induce hemolytic anemia include malaria, other protozoa, and a wide variety of gram-positive and gram-negative organisms Hemolysis secondary to infection requires rapid identification and prompt treatment When hemolysis is a result of small-vessel disease, treatment of the underlying disorder (e.g., collagen vascular disease) or primarily affected organs (e.g., renal failure in hemolytic-uremic syndrome) is the first priority The prompt institution of plasma exchange for TTP can be lifesaving Clinical Indications for Discharge or Admission Hospitalize patients with severe or symptomatic anemia or an unclear clinical trajectory for close clinical monitoring and treatment Frequently, a critical care setting is appropriate for these patients Consider outpatient management in patients with a clear or well-established underlying diagnosis and mild anemia with short-interval follow-up for monitoring and ongoing management METHEMOGLOBINEMIA Goals of Treatment Methemoglobin (MHb) is the end product of a number of mechanisms (toxic exposure, dietary trigger, acidosis, genetic abnormality) that oxidize the iron associated with a heme group from the ferrous (Fe2+ ) to ferric state (Fe3+ ) rendering it unable to reversibly bind oxygen In high quantities, insufficient gas exchange may be incompatible with life The primary goal of treatment is to remove the causative agent, provide supportive care to optimize end-organ oxygenation, and allow time for reduction of MHb back to hemoglobin In symptomatic and life-threatening situations, therapeutic intervention can hasten the reduction process CLINICAL PEARLS AND PITFALLS Suspect MHb when a cyanotic patient has a normal arterial PO2 , and pulse oximetry (generally in the mid 80s) is significantly lower than the oxygen saturation reported on arterial blood gas MHb levels are reported as percent of total hemoglobin; therefore, patients with anemia will manifest more symptoms at lower levels of MHb Methylene blue administration for methemoglobinemia is contraindicated in patients with G6PD Clinical Considerations