BACKGROUND: Intraoperative administration of crystalloid for plasma volume expansion may be reduced by use of hyperoncotic albumin. However, the degree of plasma volume expansion with administration of 20% albumin is poorly quantitated. We estimated the amount of volume expansion attributable to 20% albumin administration in patients undergoing surgery for more than 5 hours. METHODS: Twenty percent albumin was delivered at 3 mL/kg by intravenous infusion during 30 minutes to 15 patients (mean ± standard deviation [SD] age; 46 ± 15 years) undergoing surgery. Blood samples and urine were collected for 5 hours. Mass balance calculations and volume kinetics were used to estimate plasma volume expansion and capillary leakage of albumin and fluid. RESULTS: Administration of 20% albumin was associated with an increase in plasma volume amounting to 1.7 times the infused volume. After correction for hemorrhage, the median (and 25th to 75th percentiles) intravascular half-life for the administered albumin mass was 20.4 (14.2-34.7) hours. The plasma volume decreased with a half-life of 21.7 (16.1-26.8) hours. Urinary excretion was 3 times greater than the infused volume of albumin, but kinetic analysis suggested that other flows of fluid to and from the plasma occurred more slowly than previously found in volunteers. Hemodynamic support with norepinephrine increased urinary excretion and contracted the plasma volume. CONCLUSIONS: Albumin (20%) increased the plasma volume by 1.7 times the infused volume. Our results do not support that the transcapillary leakage of albumin is accelerated by anesthesia and surgery. (Anesth Analg 2022;134:1270-9) KEY POINTS• Question: What is the magnitude of plasma volume expansion with intravenous administration of 20% albumin during surgery? • Findings: The plasma volume increased by 1.7 times the infused volume of 20% albumin in patients undergoing surgical procedures lasting more than 5 hours. • Meaning: Twenty percent albumin increases plasma volume by more than the infused volume during lengthy surgery. GLOSSARYASA = American Society of Anesthesiologists; BW = body weight; CI = confidence interval; CONSORT = Consolidated Standards of Reporting Trials; COP = colloid osmotic pressure; CRP = C-reactive protein; CV = coefficient of variation; EDTA = ethylenediaminetetraacetic acid; FOCE ELS = First Order Conditional Estimation Extended Least-Squares; Hgb = hemoglobin; IV = intravenous; k 10 = elimination rate constant for albumin or fluid leaving the kinetic system; k 21 = rate constant for absorption of fluid for the extravascular (interstitial) fluid space to V c ; k b = fluid eliminated from the kinetic system but not recovered as urine; k bleed = rate constant for plasma loss with hemorrhage and blood sampling; MAP = mean arterial pressure; NLME = nonlinear mixed effect; NT-proBNP = aminoterminal prohormone brain natriuretic peptide; R 0 = rate of infusion; SD = standard deviation; Spo 2 = peripheral capillary oxygen saturation; STROBE = Strengthening the Reporting of Observational Stud...

Background The transcapillary leakage of albumin is increased by inflammation and major surgery, but whether exogenous albumin also disappears faster is unclear. Methods An intravenous infusion of 3 mL/kg of 20% albumin was given over 30 min to 70 subjects consisting of 15 healthy volunteers, 15 post-burn patients, 15 patients who underwent surgery with minor bleeding, 10 who underwent surgery with major bleeding (mean, 1.1 L) and 15 postoperative patients. Blood Hb and plasma albumin were measured on 15 occasions over 5 h. The rate of albumin disappearance from the plasma was quantitated with population kinetic methodology and reported as the half-life (T1/2). Results No differences were observed for T1/2 between volunteers, post-burn patients, patients who underwent surgery with minor bleeding and postoperative patients. The T1/2 averaged 16.2 h, which corresponds to 3.8% of the amount infused per h. Two groups showed plasma concentrations of C-reactive protein of approximately 60 mg/L and still had a similarly long T1/2 for albumin. By contrast, patients undergoing surgery associated with major hemorrhage had a shorter T1/2, corresponding to 15% of the infused albumin per h. In addition, our analyses show that the T1/2 differ greatly depending on whether the calculations consider plasma volume changes and blood losses. Conclusion The disappearance rate of the albumin in 20% preparations was low in volunteers, in patients with moderately severe inflammation, and in postoperative patients.