Time course of hemoglobin concentrations in nonbleeding intensive care unit patients

OBJECTIVES: To evaluate the time course of hemoglobin concentrations in nonbleeding intensive care unit patients. DESIGN: Prospective, observational study. SETTING: Multidisciplinary (medicosurgical) department of intensive care. PATIENTS: Ninety-one patients with no evidence of recent or active blood loss, no history of hematologic disease or chronic renal failure, and no need for extracorporeal epuration techniques. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Data collection included primary diagnoses, Acute Physiology and Chronic Health Evaluation II and sepsis-related organ failure assessment scores, signs of sepsis, 24-hr fluid balance, and hemoglobin concentrations. For the entire intensive care unit stay, the fall in hemoglobin concentrations (calculated from the mean of individual slopes of hemoglobin concentrations over time) averaged 0.52 +/- 0.69 g/dL/day. For the 33 patients who stayed in the intensive care unit for >3 days, this decline was larger for the first 3 days than for subsequent days (0.66 +/- 0.84 g/dL/day vs. 0.12 +/- 0.29 g/dL/day; p0.5 g/dL/day during the first days of intensive care unit stay in nonbleeding patients. Beyond the third day, hemoglobin concentrations can remain relatively constant in nonseptic patients but continue to decrease in septic patients, as well as patients with high sepsis-related organ failure assessment or Acute Physiology and Chronic Health Evaluation II scores. These observations may help in the interpretation of hemoglobin concentrations in critically ill patients.