title: Red blood cell 2,3-diphosphoglycerate concentration and in vivo P50 during early critical illness.
abstract: OBJECTIVE
  To measure red blood cell 2,3-diphosphoglycerate (RBC 2,3-DPG) concentrations in early critical illness; to investigate factors associated with high or low RBC 2,3-DPG levels; to calculate in vivo P50 in patients with early critical illness; and to explore the relationship between RBC 2,3-DPG and intensive care mortality.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  General medical-surgical intensive care unit (ICU) of a major Scottish teaching hospital.
  
  
  METHODS
  One-hundred eleven critically ill patients during the first 24 hrs in the ICU with no history of chronic hematologic disorders or RBC transfusion within 24 hrs and 34 age- and sex-matched healthy reference subjects.
  
  
  METHODS
  None.
  
  
  RESULTS
  We measured RBC 2,3-DPG concentration, plasma biochemistry values, and arterial blood gas parameters. On average, RBC 2,3-DPG was lower among critically ill patients than controls (mean [sd], 14.1 [6.3] vs. 16.7 [3.7] mumol/g hemoglobin; p = .004) and had a wider range of values (patients, 3.2-32.5 mumol/g hemoglobin; reference group, 9.1-24.3). Regression analysis indicated a strong independent association between plasma pH and RBC 2,3-DPG (B, 32.15 [95% confidence interval, 19.07-46.22], p < .001) and a weak association with plasma chloride (B, -0.196 [95% confidence interval, -0.39 to -0.01], p = .044) but not with hemoglobin or other measured biochemical parameters. The mean calculated in vivo P50 level was normal (3.8 kPa) but varied widely among patients (range, 2.0-5.5 kPa). RBC 2,3-DPG concentration was similar for ICU survivors and nonsurvivors.
  
  
  CONCLUSIONS
  RBC 2,3-DPG concentrations vary widely among critically ill patients. Acidosis is associated with lower RBC 2,3-DPG concentrations, but anemia is not associated with a compensatory increase in RBC 2,3-DPG early in critical illness. Lower RBC 2,3-DPG concentrations during the first 24 hrs of intensive care are not associated with higher ICU mortality.
authors.affiliation: Department of Anaesthetics, Critical Care, and Pain Medicine, The University of Edinburgh, Royal Infirmary, Little France, Edinburgh, Scotland.
authors.forename: Ezz el din S
authors.initials: Eel D
authors.lastname: Ibrahim
authors.forename: Stuart A
authors.initials: SA
authors.lastname: McLellan
authors.forename: Timothy S
authors.initials: TS
authors.lastname: Walsh
mesh_terms: D019794:2,3-Diphosphoglycerate / Q000378:metabolism*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001784:Blood Gas Analysis; D016022:Case-Control Studies; D015331:Cohort Studies; D003422:Critical Care; D016638:Critical Illness; D004912:Erythrocytes / Q000378:metabolism*; D005260:Female; D006452:Hemoglobinometry; D006801:Humans; D008297:Male; D008875:Middle Aged; D010108:Oxyhemoglobins / Q000378:metabolism*; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D010108:Oxyhemoglobins; D019794:2,3-Diphosphoglycerate