Exchange transfusion for malaria and Babesia infection

Malaria accounts for about 2 million deaths per year. Although most cases occur in children in sub-Saharian Africa, fatal infections are seen increasingly in industrialized countries. In 1992, over 900 malaria cases were reported in the United States and a third of these were caused by Plasmodium falciparum. Fatal infections are related to the magnitude of the parasitemia and the immune status of the host. P falciparum poses the greatest threat of death because it invades red cells of all ages, is often drug resistant, and is the only one of the plasmodia species that produces microvascular disease. The risk of death is correlated with the parasite load in immune naive individuals. Babesiosis is generally a subclinical infection in most normal hosts, but it can be life threatening in asplenic patients, older, or immunocompromised individuals. The role of exchange transfusion (ET) in the treatment of these infections is controversial. The Centers for Disease Control recommends that ET be performed in P falciparum infection when parasitemia is equal or greater than 10%. In patients with coma, renal failure, or adult respiratory distress syndrome, ET is recommended regardless of the level of parasitemia even if less than 10%. ET has been advocated to reduce the level of parasitized red blood cells (RBCs), to remove cytokines, and to improve the rheologic properties of the blood. Dramatic improvement has been reported, but there are conflicting reports that question the need for exchange transfusion. This review examines the pathophysiology of severe infection and its treatment, with an emphasis on the role of exchange transfusion.