ELEVATED LEVELS OF METHEMOGLOBIN IN TANZANIAN CHILDREN WITH SEVERE AND UNCOMPLICATED MALARIA

Elevated levels of methaemoglobin, the ferric form of haemoglobin inca pable of oxygen transport, have been previously found during Plasmodiu m vivax infections and in acidotic infants. We measured methaemoglobin in the following 5 groups of children with P. falciparum malaria admi tted to Muhimbili Medical Centre, Dar es Salaam, Tanzania. (i) Cerebra l malaria (CM) with unrousable coma (n=50), including 32 with complete recovery (CMCR) and 18 with death or neurological sequelae (CMDS); (i i) malaria with severe anaemia but without severe respiratory distress (SA; n=6); (iii) uncomplicated malaria (UM; n=37); (iv) asymptomatic parasitaemia (AP; n=5); and (v) healthy controls (HC; n=34). Mean meth aemoglobin levels were elevated in all groups with malaria, forming up to 164% of circulating haemoglobin. The degree of methaemoglobinaemia correlated with disease severity and severity of anaemia. Mean methae moglobin levels in children with AP, UM, SA, CMCR and CMDS were 3.3%, 4.1%, 5.6%, 4.7% and 5.8% respectively; the mean levels in those with clinical disease were significantly higher than those in healthy contr ols (2.0%). Methaemoglobinaemia >10% was found in 5.4%, 16.7%, 12.5% a nd 22.2% of those with UM, SA, CMCR and CMDS, respectively. In the pre sence of parasite sequestration, impaired tissue perfusion, and a redu ction in oxygen carrying capacity of blood due to anaemia, a further r eduction in oxygen carrying capacity from even a modest concentration of methaemoglobin is likely to exacerbate tissue hypoxia, perhaps crit ically so in a minority of anaemic and acidotic patients with severe f alciparum malaria.