Time course of anemia during six months follow up following intensive care discharge and factors associated with impaired recovery of erythropoiesis

Abstract

Objectives: Anemia is a common complication of critical illness, but its duration after intensive care discharge and possible contributory factors have not been studied. Our aim was to follow patients discharged anemic from the intensive care unit (ICU) for up to 6 months and determine the duration of and possible reasons for persisting anemia.

Design: Prospective observational cohort study of intensive care (ICU) survivors with moderate-severe anemia at the time of ICU discharge. Erythropoietic and inflammatory markers were measured at regular intervals over six months to assess red cell production and factors limiting recovery from anemia.

Setting: An 18-bed medico-surgical ICU in a Scottish university teaching hospital.

Patients: Patients who required >24 hrs of ventilatory support and were discharged from intensive care with hemoglobin < 100 g/L were studied prospectively over 6 months. 30 patients were recruited; 19 completed 6 months follow-up, 6 died during the study period, and 5 completed part of the follow up. Patients with ongoing renal failure or chronic hematologic disorders were excluded.

Measurements and main results: 47% (9 of 19) of patients completing 6 months follow up recovered from their anemia. The median time to recovery was 11 wks (1, 3 quartiles: 9, 26 wks). 10 patients (53%) were still anemic 6 months after ICU discharge. No patients developed iron, vitamin B12 or folate deficiency. An inappropriately low erythropoietin response to anemia was observed in virtually all patients and did not distinguish nonrecovering patients. Patients with delayed recovery or persisting anemia during the 13 wks following ICU discharge had higher levels of circulating inflammatory markers (IL-6 and C-reactive protein) and did not exhibit reticulocytosis during the weeks following discharge.

Conclusions: Anemia persists in many patients following critical illness and is associated with ongoing inflammation, inappropriate erythropoietin response and poor marrow red cell production.