Abstracts and Programme: EUROANAESTHESIA 2011: The European Anaesthesiology Congress: ESA Best Abstract Prize Competition (BAPC)
Background and Goal of Study: Patients admitted to surgery are often dehydrated which might require cardiac output monitoring (goal-directed fluid therapy) to be corrected. This study proposes that even modest dehydration can be detected by kinetic analysis based on the Hb dilution following an infusion of acetated Ringer's solution.
Materials and Methods: Forty experiments were performed in 10 male healthy volunteers with a mean age of 22 years. All 10 underwent 4 experiments in random order that were separated by at least two days. The four arms consisted of infusing either 5 ml/kg or 10 ml/kg of Ringer's over 15 min. For both volumes, the volunteer was either in the euhydrated or dehydrated state. Dehydration of 1.5-2.0 L (about 2% of the body weight) was induced by repeatedly injecting 5 mg of furosemide. Sixty minutes were then allowed between the last dose of furosemide and the infusion of Ringer's. The venous Hb concentration was measured every 5 min during the first 50 min and then at 60, 70, 90 105 and 120 min. The Hb series was analyzed for the volume of distribution and fluid clearance according to a one-volume fluid model (1). The results are given as the median and 25th-75th percentiles. Two-way ANOVA based on In-transformed data was used for statistics; the tested predictors were the infused volume and the presence of dehydration.
Results and Discussion: The volume of distribution did not differ significantly between the 4 experiments, but the fluid clearance differed by a factor of 3 between the euhydrated and dehydrated state. The overall clearance during normohydration was 152 (95-218) ml/min as compared to 50 (35-66) in dehydration (P< 0.001). The half-life of the infused fluid also differed greatly depending on the hydration status. In euhydration the half-life was 23 (12-37) min and in dehydration 76 (57-101) min. There was no benefit from infusing 10 ml/kg instead of 5 ml/kg. Using a cut-off of 90 ml/min, the fluid clearance predicted the presence of dehydration by a sensitivity of 1.0 and a specificity of 0.9. The same sensitivy and specificty was obtained when using a cut-off point of 40 min for the half-life.
Conclusions: Dehydration of 2% of the body weight can be detected from the Hb response to infusion of a small volume of Ringer's solution.
(1) Hahn RG. Volume kinetics of infusion fluids (review). Anesthesiology 2010; 113: 470-481.
Acknowledgement: The study was financed as part of an ESA grant.