Functional iron deficiency, infection and systemic inflammatory response syndrome in critical illness

To investigate the prevalence and clinical relevance of functional iron def iciency in the critically ill, we performed a prospective observational stu dy in a university hospital general intensive care unit. We collected patie nt demographics, severity of illness data, haematological and biochemical v ariables in 51 consecutive admissions. We recorded episodes of culture posi tive infection. Functional iron deficiency (FID), measured by red cell hypochromasia on flo w cytometry, was present in 35% of patients at admission to intensive care. FID patients were of similar age, diagnosis, APACHE score, sequential orga n failure assessment (SOFA) score, haemoglobin, serum B12, folate and ferri tin to patients without FID. However; patients with FID had a prolonged int ensive care stay compared with non-FID patients (P <0.001) and increased ti me to hospital discharge (P=0.09). Duration of intensive care stay correlat ed with severity of FID (r=0.33, P <0.02). Systemic inflammatory response s yndrome (SIRS) was present for longer in those with FID (P <0.02). Overall mortality did not differ between groups. No difference was seen in the inci dence of positive cultures between those with FID (9/18 patients) and those without FID (15/33 patients). FID was independently associated only with a bnormal white blood cell count (WBC <4 or > 11 x 10(9).l(-1)) at admission to ICU, P=0.007, but not with positive cultures. There is a high prevalence of FID in intensive care, associated with an inc reased duration of stay and duration of SIRS. We have been unable to demons trate a link with infection, either as a predisposing factor or as an acute response.