The predictive performance of infusion strategy nomogram based on a fluid kinetic model / 대한마취과학회지

BACKGROUND: In a previous study, fluid kinetic models were applied to describe the volume expansion of the fluid space by administration of crystalloid and colloid solutions. However, validation of the models were not performed, it is necessary to evaluate the predictive performance of these models in another population. METHODS: Ninety five consenting patients undergoing elective spinal surgery under general anesthesia were enrolled in this study. These patients were randomly assigned to three fluid groups i.e. Hartmann's solution (H group, n = 28), Voluven(R) (V group, n = 34), and Hextend(R) (X group, n = 33). After completion of their preparation for surgery, the patients received a loading and maintenance volume of each fluid predetermined by nomograms based on fluid pharmacokinetic models during the 60-minute use of an infusion pump. Arterial samples were obtained at preset intervals of 0, 10, 20, and 30 min after fluid administration. The predictive performances of the fluid kinetic modes were evaluated using the fractional change of arterial hemoglobin. The relationship between blood-volume dilution and target dilution of body fluid space was also evaluated using regression analysis. RESULTS: A total of 194 hemoglobin measurements were used. The bias and inaccuracy of these models were -2.69 and 35.62 for the H group, -1.53 and 43.21 for the V group, and 9.05 and 41.82 for the X group, respectively. The blood-volume dilution and target dilution of body-fluid space showed a significant linear relationship in each group (P < 0.05). CONCLUSIONS: Based on the inaccuracy of predictive performance, the fluid-kinetic model for Hartmann's solution showed better performance than the other models.

Effects of anesthesia on fluid volume kinetics after infusion of colloid solution during blood donation / 대한마취과학회지

BACKGROUND: The fluid kinetics of intravenously infused colloid during inhalation anesthesia and hemorrhage have not been investigated. We therefore assessed fluid space changes during infusion of hydroxyethyl starch solution after hemorrhage in conscious and desflurane-anesthetized individuals. METHODS: Following the donation of 400 ml of blood, 500 ml of hydroxyethyl starch solution was infused over 20 minutes into wakeful and desflurane-anesthetized volunteers. Blood was repeatedly sampled to measure hemoglobin concentration, a marker of plasma dilution, and fluid kinetic analysis was performed to evaluate changes in fluid space. RESULTS: Using a fluid kinetic model, we found that the mean volume of fluid space was 7,724 +/- 1,788 ml in wakeful volunteers and 6,818 +/- 4,221 ml in anesthetized volunteers, and the elimination rate constants were 7.1 +/- 3.5 ml/min and 19.4 +/- 4.6 ml/min, respectively. CONCLUSIONS: Infusion of colloid after mild hemorrhage resulted in similar expansions of plasma volume in desflurane-anesthetized and conscious individuals. During anesthesia, however, the expansion of plasma volume by colloid was decreased and of shorter duration than observed in conscious patients.

Modelling the Expandable Body Fluid Space after I.V. Fluid Infusion / 대한마취과학회지

BACKGROUND: Changes in the volume of the fluid space expanded by i.v. infusion of crystalloid solution have been analysed recently using mathematical models. The models are based on the assumption that the body strives to maintain volume homeostasis of fluid spaces and that the rate of restoration is a function of deviation from resting volume. METHODS: In this work mathematical models were developed to represent the kinetics of volume changes of fluid spaces associated with infusion of Ringer's solution. Based on the characteristics of fluid transportation, two expansion models were tested. The single-fluid space model has a single volume into which fluid is fed and from which fluid is left, and the two-fluid space model has another space in addition to the first volume so that fluid exchanges between these two spaces are possible. Volunteers (six men) were given Hartman's solution for 30 min and the changes in blood hemoglobin were detected. RESULTS: From the comparison with experimental data, the single-fluid space model was found to represent adequately in all volunteers, however, two-fluid space model was found to represent 75% of volunteers. CONCLUSIONS: These models may be useful in the description and analysis of the effects of i.v. fluid therapy.