Detection of dehydration by using volume kinetics

R. G. Hahn, J. Zdolsek, Y. Li
2011 European Journal of Anaesthesiology  
Running head: Kinetic analysis of dehydration Author's contributions: Zdolsek planned and organized the experiments. Li conducted the experiments. Hahn made the study design, completed the data analysis, and wrote the manuscript. Implications statement: A study of volunteers shows that dehydration of 2% of body weight can be detected from the dilution of the blood hemoglobin concentration following an infusion of only 5 ml/kg of Ringer's solution. Abstract Background: Patients admitted to
more » ... s admitted to surgery may be dehydrated, which is difficult to diagnose except when it is severe (>5% of the body weight). This study hypothesizes that modest dehydration can be detected by kinetic analysis of the blood hemoglobin (Hgb) concentration following a bolus infusion of crystalloid fluid. Methods : Four series of experiments were performed on 10 conscious, healthy male volunteers. Separated by at least two days, they received 5 ml/kg or 10 ml/kg of acetated Ringer's over 15 min. Before starting half of the intravenous infusions, volume depletion amounting to 1.5-2.0 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 Hgb over 120 min. The perfusion index and the pleth variability index were monitored by pulse oximetry following a change of body position. Results and Discussion: Dehydration decreased the elimination clearance of acetated Ringer´s [median (25 th -75 th percentile)] from 1.84 (1.23-2.57) to 0.53 (0.41-0.79) ml/kg/min (Wilcoxon´s 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. Conclusion: 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 of Ringer's solution. Word count: 3,974
doi:10.1097/00003643-201106001-00002 fatcat:zcbjfh7lmnejhgatyo5jpk5pqy