Mechanism of anaemia in experimental bacterial endocarditis.

Rabits with Streptococcus viridans aortic valve endocarditis develop anaemia and reticulocytosis which increase with the duration of infection. Mean red cell counts decreased from 6.05 +/- 0.29 X 10(6) per mul before infection to 4.10 +/- 0.18 X 10(6) per mul after 11 to 20 days of endocarditis and reticulocytes increased from 1.16 +/- 0.14 X 10(5) per mul to 4.91 +/- 0.83 X 10(5) per mul after more than 20 days of endocarditis. The anaemia could not be explained by intravascular haemolysis. Anti-erythrocyte antibodies were not detected. Splenomegaly was a consistent finding and also increased with the duration of infection. Red cell half life (T1/2) was shortened to 4.7 +/- 0.3 days in rabbits with endocarditis compared with normal T1/2 of 11.1 +/- 0.5 days. The T1/2 of red cells from infected animals was prolonged when measured in noninfected rabbits and splenectomized animals had a mean red cell T1/2 of 9.25 days after three weeks of infection. These studies suggest that splenic enlargement associated with infection results in red cell sequestration, a mechanism not well recognized as contributing to the anaemia of endocarditis.