title: Detection of dehydration by using volume kinetics.
abstract: BACKGROUND
  Patients admitted to surgery may be dehydrated, which is difficult to diagnose except when it is severe (>5% Gl116 of the body weight). We hypothesized that modest dehydration can be detected by kinetic analysis of the blood hemoglobin concentration after a bolus infusion of crystalloid fluid.
  
  
  METHODS
  Four series of experiments were performed on 10 conscious, healthy male volunteers. Separated by at least 2 days, they received 5 or 10 mL/kg acetated Ringer's solution over 15 minutes. Before starting half of the IV infusions, volume depletion amounting to 1.5 to 2.0 L (approximately 2% of body weight) was induced with furosemide. The elimination clearance and the half-life of the infused fluid were calculated based on blood hemoglobin over 120 minutes. The perfusion index and the pleth variability index were monitored by pulse oximetry after a change of body position.
  
  
  RESULTS
  Dehydration decreased the elimination clearance of acetated Ringer's solution [median (25th-75th percentile)] from 1.84 (1.23-2.57) to 0.53 (0.41-0.79) mL/kg/min (Wilcoxon matched-pair test P < 0.001) and increased the half-life from 23 (12-37) to 76 (57-101) minutes (P < 0.001). The smaller infusion, 5 mL/kg, fully discriminated between experiments performed in the euhydrated and dehydrated states, whereas the urinary excretion provided a less-reliable indication of hydration status. Dehydration decreased the perfusion index but did not affect the pleth variability index.
  
  
  CONCLUSIONS
  Dehydration amounting to 2% of the body weight could be detected from the elimination clearance and the half-life of an infusion of 5 mL/kg Ringer's solution.
authors: Department of Anesthesia, Faculty of Health Sciences, Linköping University, Linköping, Sweden.
authors: Joachim
authors: J
authors: Zdolsek
authors: Yuhong
authors: Y
authors: Li
authors: Robert G
authors: RG
authors: Hahn
mesh_terms: D000328:Adult; D001810:Blood Volume / Q000187:drug effects / Q000502:physiology*; D003681:Dehydration / Q000097:blood* / Q000139:chemically induced / Q000175:diagnosis*; D004232:Diuretics / Q000008:administration & dosage / Q000493:pharmacokinetics; D005665:Furosemide / Q000008:administration & dosage / Q000493:pharmacokinetics; D006801:Humans; D007552:Isotonic Solutions / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008297:Male; D008954:Models, Biological; D000077331:Ringer's Solution; D055815:Young Adult
chemical_list: D004232:Diuretics; D007552:Isotonic Solutions; D005665:Furosemide; D000077331:Ringer's Solution