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Background: Although hyperoncotic albumin may be used to recruit oedema, its effectiveness remains unclear. Therefore, this issue was studied during infusion experiments in healthy volunteers.Method: Fifteen healthy volunteers (mean age 31 years) received an infusion of 3 mL/kg of 20% albumin over 30 minutes. Their urinary excretion was recorded, and venous blood samples were taken to measure blood haemoglobin (Hb), haematocrit, colloid osmotic pressure as well as plasma albumin and sodium concentrations on 15 occasions over a period of 300 minutes. Plasma volume expansion was taken as the inverse of the fluid-induced dilution of venous plasma, as given by the blood Hb concentration. Mass balance calculations were used to estimate the mobilisation of fluid from the tissues.Results: Maximum plasma volume expansion was reached 20 minutes after completing an infusion of 20% albumin. Urinary excretion was effectively increased, and the mobilised fluid from the tissues at 300 minutes amounted to 3.4 ± 1.2 mL for each infused mL of 20% albumin, of which 19% was of intracellular origin. The urinary excretion correlated strongly with the amount of recruited fluid (R2  = 0.87) and inversely with the plasma volume expansion (R2  = 0.53).Conclusion: The infusion of 20% albumin significantly increases the plasma volume by recruiting interstitial fluid. After completing the infusion, there is a delay of 20 minutes until maximum plasma dilution is reached, and the duration of the plasma volume expansion lasts far beyond 5 hours. [ABSTRACT FROM AUTHOR]

Background: Crystalloid fluid requires 30 min for complete distribution throughout the extracellular fluid space and tends to cause long-standing peripheral edema. A kinetic analysis of the distribution of Ringer's acetate with increasing infusion rates was performed to obtain a better understanding of these characteristics of crystalloids.Methods: Data were retrieved from six studies in which 76 volunteers and preoperative patients had received between 300 ml and 2375 ml of Ringer's acetate solution at a rate of 20-80 ml/min (0.33-0.83 ml/min/kg). Serial measurements of the blood hemoglobin concentration were used as inputs in a kinetic analysis based on a two-volume model with micro-constants, using software for nonlinear mixed effects.Results: The micro-constants describing distribution (k12) and elimination (k10) were unchanged when the rate of infusion increased, with half-times of 16 and 26 min, respectively. In contrast, the micro-constant describing how rapidly the already distributed fluid left the peripheral space (k21) decreased by 90% when the fluid was infused more rapidly, corresponding to an increase in the half-time from 3 to 30 min. The central volume of distribution (V(c)) doubled.Conclusion: The return of Ringer's acetate from the peripheral fluid compartment to the plasma was slower with high than with low infusion rates. Edema is a normal consequence of plasma volume expansion with this fluid, even in healthy volunteers. The results are consistent with the view that the viscoelastic properties of the interstitial matrix are responsible for the distribution and redistribution characteristics of crystalloid fluid. [ABSTRACT FROM AUTHOR]

Background: During fluid infusion therapy, plasma proteins are diluted and leak from the intravascular space, which alters the colloid osmotic pressure (COP) and potentially affects coagulation. We hypothesised that acetated Ringer's and starch solution, alone or in combination, influence these mechanisms differently.Materials and Methods: On different occasions, 10 male volunteers were infused with 20 ml/kg acetated Ringer's and 10 ml/kg 6% hyroxyethyl starch 130/0.4 (Voluven(®) ) alone or in combination (first with starch solution followed by Ringer's solution). Blood samples were collected every 30-min for measurements of COP, blood haemoglobin, platelets, and plasma concentrations of albumin, immunoglobulins (IgG and IgM), coagulation factor VII (FVII), fibrinogen, cystatin C, activated partial thromboplastin time (APTT) and prothrombin international normalised ratio (PT-INR). Changes were compared with the haemoglobin-derived plasma dilution.Results: The COP increased by 8.4% (SD 3) with starch and decreased by 26.2% (7.9) with Ringer's. These infusions diluted the plasma by 23.4% (5.3) and 18.7% (4.9) respectively. The COP changes in the combined experiment followed the same pattern as the individual infusions. Albumin and IgG changes in excess of the plasma dilution were very subtle. The intravascular contents of the IgM and platelets decreased, whereas FVII, fibrinogen and cystatin C increased. PT-INR increased by 1/3 of the plasma dilution, whereas changes in APTT did not correlate with the plasma dilution.Conclusions: The starch increased COP and only minor capillary leak occurred in healthy volunteers. The fluid-induced plasma dilution correlated with mild impairment of the extrinsic coagulation pathway but not of the intrinsic pathway. [ABSTRACT FROM AUTHOR]

Background: A commercially available pulse oximeter that reports blood haemoglobin (Hb) concentration is evaluated. This study considers whether this device can provide serial Hb data that would be sufficiently reliable for volume kinetic analysis of infusion fluids. Methods: Forty infusions of 5 or 10 ml/kg of acetated Ringer's solution were given over 15 min in 10 healthy volunteers. Hb was measured on 17 different occasions over 120 min using the Radical 7 pulse oximeter and compared with the result of invasive blood sampling (control). A one-volume kinetic model was applied to each data series. The pulse oximeter also reported the perfusion index (PI). Results: The median deviation between the 680 invasive and non-invasive Hb samples (the accuracy) was 1.6% and the absolute median deviation (precision) was 4.6%. Between-subject factors explained half of the variation in the difference between non-invasive vs. invasive sampling. Ten of the 40 non-invasive series of Hb values were discarded from kinetic analysis due to poor quality. The remaining 30 series showed a smaller distribution volume for the infused fluid when kinetic analysis was based on the non-invasive method (3.0 vs. 5.3 l; P<0.001). This was due to co-variance with the PI, which exaggerated the decrease in Hb caused by the infusions. The non-invasive method might provide useful kinetic data at the group level, but individual curves deviated too much from the invasive data to be reliable. Conclusions: Non-invasive measurement of the Hb concentration during volume loading could not provide useful kinetic data for individuals. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented related to Nephrocheck, an apparatus for early detection of acute kidney injury (AKI).

Background: Elevated plasma concentrations of syndecan-1 and heparan sulfate in studies of trauma, sepsis, and major surgery are commonly assumed to indicate acute glycocalyx degradation. We explored a possible role of the kidneys for these elevations., Methods: Plasma and urine concentrations of syndecan-1, heparan sulfate, and biomarkers of inflammation were measured over 5 hours in 15 hospital patients treated for post-burn injury. The renal clearances of syndecan-1 and heparan sulfate (CL R ) were calculated and their influence on the plasma concentration predicted by simulation., Results: The urine/plasma concentration ratio was 0.9 (0.3-3.0) for syndecan-1 and 2.8 (2.0-4.3) for heparan sulfate. The CL R varied 250-fold for syndecan-1 and 10-fold for heparan sulfate. Multiple linear regression analysis showed that CL R for syndecan-1 was positively associated with the creatinine clearance (P < .0032) and the urine flow (P < .015). CL R for heparan sulfate increased with interleukin-6 (P < .003) and the urine flow (P < .01). Simulations suggested that a change in CL R from the mean of the highest 3 to the lowest three values would double plasma syndecan-1 within 4 hours and cause a 7-fold rise after 24 hours. A similar change in CL R for heparan sulfate would triple the plasma level within 24 hours, even if no increased shedding of the glycocalyx takes place., Conclusions: The renal elimination of syndecan-1 and heparan sulfate varied greatly. A change in kidney function, which is common after trauma and major surgery, might alone induce several-fold changes in their plasma concentrations., (© 2021 The Authors. Acta Anaesthesiologica Scandinavica published by John Wiley & Sons Ltd on behalf of Acta Anaesthesiologica Scandinavica Foundation.)

The Revised (or "Extended") Starling principle is based on highly controlled laboratory-based frog and rodent experiments and remains a hypothesis awaiting clinical validation. A key point is that the endothelial glycocalyx layer moves the oncotic gradient from being between the plasma and the interstitium to between the plasma and a virtually protein-free space between the glycocalyx and the endothelial cell membrane, which dramatically changes the prerequisites for fluid absorption from tissue to plasma. However, many experimental and clinical observations in humans agree poorly with the new microcirculatory proposals. The most troubling aspect of the explanation regarding the role of the glycocalyx in the Revised Starling principle is the effective reabsorption of fluid by skeletal muscle when the capillary filtration pressure is acutely reduced. Other issues include the plasma volume effects of hypertonic saline, iso-oncotic and hyper-oncotic albumin, fluid distribution during cardio-pulmonary bypass, and the virtually identical capillary leakage of plasma and albumin despite marked inflammation found in our fluid therapy studies. The Revised Starling principle deals mainly with steady-state conditions, but the circulatory system is highly dynamic. Second to second vasomotion is always operational and must be considered to understand what we observe in humans., (© 2020 The Authors. Acta Anaesthesiologica Scandinavica Foundation published by John Wiley & Sons Ltd on behalf of Acta Anaesthesiologica Scandinavica Foundation.)

Aims: A population kinetic model was developed for the body fluid shifts occurring when 20% albumin is given by intravenous infusion. The aim was to study whether its efficacy to expand the plasma volume is impaired after major surgery., Methods: An intravenous infusion of 3 mL/kg 20% albumin over 30 minutes was given to 15 volunteers and to 15 patients on the 1 st day after major open abdominal surgery. Blood samples and urine were collected during 5 hours. Mixed-effect modelling software was used to develop a fluid volume kinetic model, using blood haemoglobin and urine excretion the estimate body fluid shifts, to which individual-specific covariates were added in sequence., Results: The rise in plasma albumin expanded the plasma volume in excess of the infused volume by relocating noncirculating fluid (rate constant k 21 ), but it also increased losses of fluid from the kinetic system (k b ). The balance between k 21 and k b maintained the rise in plasma albumin and plasma volume at a virtual steady-state for almost 2 hours. The rate constant for urinary excretion (k 10 ) was slightly reduced by the preceding surgery, by a marked rise in plasma albumin, and by a high preinfusion urinary concentration of creatinine. The arterial pressure, body weight, and plasma concentrations of C-reactive protein and shedding products of the endothelial glycocalyx layer (syndecan-1, heparan sulfate, and hyaluronic acid) did not serve as statistically significant covariates., Conclusions: There were no clinically relevant differences in the kinetics of 20% albumin between postoperative patients and volunteers., (© 2019 The British Pharmacological Society.)