TIME COURSE OF IRON METABOLISM IN CRITICALLY ILL PATIENTS

Background: Altered iron metabolism plays a central role in the development of anaemia in critically ill patients but the time course of iron status in septic and non-septic critically ill patients has not been well defined. Methods: Prospective study in a 34-bed medico-surgical ICU. The complete blood count, iron, ferritin, transferrin, and transferrin receptor concentrations, transferrin saturation and C-reactive protein (CRP) concentrations were measured on days 1,3 and 5 of the ICU stay in 95 consecutive ICU patients (33 with sepsis and 62 without). Results: Despite an identical complete blood count on day 1, septic patients had significantly lower iron concentrations (21[13-34] vs 50[28-75] mu g/dL,p < 0.001), transferrin concentrations (169[121-215] vs 214[173247] nng/dL; p = 0.003), and transferrin saturation (11[7-15] vs 19[11-25]%; p = 0.004), and higher ferritin concentrations (432[184-773] vs 204[78-354] ng/mL; p = 0.002) than non-septic patients. These alterations were associated with a lower reticulocyte count (42[29-61] vs 58[48-77] x 10(3)/mm(3); p = 0.028). On day 1, CRP concentrations, which were higher in septic than in non-septic patients (20.0[13.5-27.5] vs 2.3[0.7-5.9] mg/dL; p < 0.001), were directly correlated with ferritin concentrations (rho = 0.55, p < 0.001) and inversely correlated with transferrin concentrations (rho = -0.49, p = 0.0001) and transferrin saturation (rho = -0.49, p= 0.0001). After 3 days, iron and transferrin concentrations were identical in septic and non-septic patients. Iron metabolism remained altered in both populations until the 5th day. Conclusions: Iron status is rapidly altered in critically ill patients, especially in septic patients. These alterations persist during the course of the disease and are associated with decreased erythropoiesis.