Project description:ObjectiveThe colloid osmotic pressure (COP) of plasma and interstitial fluid play important roles in transvascular fluid exchange. COP values for monitoring fluid balance in healthy and sick children have not been established. This study set out to determine reference values of COP in healthy children.Materials and methodsCOP in plasma and interstitial fluid harvested from nylon wicks was measured in 99 healthy children from 2 to 10 years of age. Nylon wicks were implanted subcutaneously in arm and leg while patients were sedated and intubated during a minor surgical procedure. COP was analyzed in a colloid osmometer designed for small fluid samples.ResultsThe mean plasma COP in all children was 25.6 ± 3.3 mmHg. Arbitrary division of children in four different age groups, showed no significant difference in plasma or interstitial fluid COP values for patients less than 8 years, whereas patients of 8-10 years had significant higher COP both in plasma and interstitial fluid. There were no gender difference or correlation between COP in interstitial fluid sampled from arm and leg and no significant effect on interstitial COP of gravity. Prolonged implantation time did not affect interstitial COP.ConclusionPlasma and interstitial COP in healthy children are comparable to adults and COP seems to increase with age in children. Knowledge of the interaction between colloid osmotic forces can be helpful in diseases associated with fluid imbalance and may be crucial in deciding different fluid treatment options.Trial registrationClinicalTrials.gov NCT01044641.
Project description:BackgroundIn clinical states associated with systemic oxidative stress (OS) and inflammation such as chronic kidney disease (CKD), oxidative modifications of serum albumin impair its quantification, resulting in apparent hypoalbuminemia. As the maintenance of oncotic pressure/colloid osmotic pressure (COP) is a major function of albumin, this study examined the impact of albumin oxidation on COP, both in-vivo and in-vitro.MethodsPatients with proteinuria and patients on chronic hemodialysis (HD) with systemic inflammation and OS were enrolled. Blood samples were collected from 134 subjects: 32 healthy controls (HC), proteinuric patients with high (n = 17) and low (n = 31) systemic inflammation and from 54 patients on chronic hemodialysis (HD) with the highest levels of OS and inflammation.ResultsIn-vitro oxidized albumin showed significantly higher COP values than non-oxidized albumin at identical albumin levels. In vivo, in hypoalbuminemic HD patients with the highest OS and inflammation, COP values were also higher than expected for the low albumin levels. The contribution to COP by other prevalent plasma proteins, such as fibrinogen and immunoglobulins was negligible. We imply that the calculation of COP based on albumin levels should be revisited in face of OS and inflammation. Hence, in hypoalbuminemic proteinuric patients with systemic OS and inflammation the assumption of low COP should be verified by its measurements.
Project description:Background and objectivesColloid osmotic pressure (COP) is a principal determinant of intravascular fluid homeostasis and a pillar of fluid therapy and transfusion. Transfusion-associated circulatory overload (TACO) is a leading complication of transfusion, and COP could be responsible for recruiting additional fluid. Study objective was to measure COP of blood products as well as investigate the effects of product concentration and storage lesion on COP.Materials and methodsThree units of each product were sampled longitudinally. COP was measured directly as well as the determinants thereof albumin and total protein. Conventional blood products, that is red blood cell (RBC), fresh-frozen plasma (FFP) and platelet concentrates (PLTs), were compared with their concentrated counterparts: volume-reduced RBCs, hyperconcentrated PLTs, and fully and partially reconstituted lyophilized plasma (prLP). Fresh and maximally stored products were measured to determine changes in protein and COP. We calculated potential volume load (PVL) to estimate volume recruited using albumin's water binding per product.ResultsColloid osmotic pressure varies widely between conventional products (RBCs, 1·9; PLTs, 7·5; and FFP, 20·1 mmHg); however, all are hypooncotic compared with human plasma COP (25·4 mmHg). Storage lesion did not increase COP. Concentrating RBCs and PLTs did not increase COP; only prLP showed a supraphysiological COP of 47·3 mm Hg. The PVL of concentrated products was lower than conventional products.ConclusionColloid osmotic pressure of conventional products was low. Therefore, third-space fluid recruitment is an unlikely mechanism in TACO. Concentrated products had a lower calculated fluid load and may prevent TACO. Finally, storage did not significantly increase oncotic pressure of blood products.
Project description:To measure colloid osmotic pressure in interstitial fluid (COP(i)) from human subcutaneous tissue with the modified wick technique in order to determine influence of topical application of anaesthetics, dry vs. wet wick and implantation time on COP(i).In 50 healthy volunteers interstitial fluid (IF) was collected by subcutaneous implantation of multi-filamentous nylon wicks. Study subjects were allocated to two groups; one for comparing COP(i) obtained from dry and saline soaked wicks, and one for comparing COP(i) from unanaesthetized skin, and skin after application of a eutectic mixture of local anaesthetic (EMLA®, Astra Zeneca) cream. IF was sampled from the skin of the shoulders, and implantation time was 30, 60, 75, 90 and 120 min. Colloid osmotic pressure was measured with a colloid osmometer. Pain assessment during the procedure was compared for EMLA cream and no topical anaesthesia using a visual analogue scale (VAS) in a subgroup of 10 subjects.There were no significant differences between COP(i) obtained from dry compared to wet wicks, except that the values after 75 and 90 min. were somewhat higher for the dry wicks. Topical anaesthesia with EMLA cream did not affect COP(i) values. COP(i) decreased from 30 to 75 min. of implantation (23.2 ± 4.4 mmHg to 19.6 ± 2.9 mmHg, p = 0.008) and subsequently tended to increase until 120 min. EMLA cream resulted in significant lower VAS score for the procedure.COP(i) from subcutaneous tissue was easily obtained and fluid harvesting was well tolerated when topical anaesthetic was used. The difference in COP(i) assessed by dry and wet wicks between 75 min. and 90 min. of implantation was in accordance with previous reports. The use of topical analgesia did not influence COP(i) and topical analgesia may make the wick technique more acceptable for subjects who dislike technical procedures, including children.ClinicalTrials.gov NCT01044979.
Project description:BackgroundSevere respiratory distress and acute kidney injury (AKI) are key factors leading to poor outcomes in patients with dengue shock syndrome (DSS). There is still limited data on how much resuscitated fluid and the specific ratios of intravenous fluid types contribute to the development of severe respiratory distress necessitating mechanical ventilation (MV) and AKI in children with DSS.Methodology/principal findingsThis retrospective study was conducted at a tertiary pediatric hospital in Vietnam between 2013 and 2022. The primary outcomes were the need for MV and renal function within 48 h post-admission. A predictive model for MV was developed based on covariates from the first 24 h of PICU admission. Changes in renal function within 48 h were analyzed using a linear mixed-effects model. A total of 1,278 DSS children with complete clinical and fluid data were included. The predictive performance of MV based on the total intravenous fluid volume administered yielded an AUC of 0.871 (95% CI, 0.836-0.905), while the colloid-to-crystalloid ratio showed an AUC of 0.781 (95% CI, 0.743-0.819) (both P < 0.001). The optimal cut-off point of the cumulative fluid infusion was 181 mL/kg, whereas that of the colloid-to-crystalloid ratio was 1.6. Multivariable analysis identified female patients, severe bleeding, severe transaminitis, excessive fluid resuscitation, and a higher proportion of colloid solutions in the first 24 h as significant predictors of MV in DSS patients. The predictive model for MV demonstrated high accuracy, with a C-statistic of 89%, strong calibration, and low Brier score (0.04). Importantly, a more pronounced decline in glomerular filtration rate was observed in DSS patients who required MV than in those who did not.Conclusions/significanceThis study provides insights into optimizing fluid management protocols, highlighting the importance of monitoring fluid volume and the colloid-to-crystalloid ratio during early resuscitation to improve the clinical outcomes of DSS patients.
Project description:Why do people give to strangers? We propose that people trust and give more to those whose emotional expressions match how they ideally want to feel ("ideal affect match"). European Americans and Koreans played multiple trials of the Dictator Game with recipients who varied in emotional expression (excited, calm), race (White, Asian) and sex (male, female). Consistent with their culture's valued affect, European Americans trusted and gave more to excited than calm recipients, whereas Koreans trusted and gave more to calm than excited recipients. These findings held regardless of recipient race and sex. We then used fMRI to probe potential affective and mentalizing mechanisms. Increased activity in the nucleus accumbens (associated with reward anticipation) predicted giving, as did decreased activity in the right temporo-parietal junction (rTPJ; associated with reduced belief prediction error). Ideal affect match decreased rTPJ activity, suggesting that people may trust and give more to strangers whom they perceive to share their affective values.
Project description:ObjectivesColloid oncotic pressure (COP) is an important factor in cardiac surgery, owing to its role in haemodilution. The effect of cardiopulmonary bypass prime fluids on the COP is unknown. In this study, the effect of crystalloid and colloid prime fluids, with or without retrograde autologous priming (RAP), on the COP during elective cardiac surgery was evaluated.MethodsRandomized controlled trials and prospective clinical trials comparing crystalloid and colloid priming fluids or with RAP were selected. The primary outcome was the COP; secondary outcomes were fluid balance, fluid requirements, weight gain, blood loss, platelet count and transfusion requirements.ResultsFrom 1582 records, 29 eligible studies were identified. COPs were comparable between gelofusine and hydroxyethyl starch (HES) during bypass [mean difference (MD): 0.69; 95% confidence interval (CI): -2.05, 3.43; P = 0.621], after bypass (MD: -0.11; 95% CI: -2.54, 2.32; P = 0.930) and postoperative (MD: -0.61; 95% CI: -1.60, 0.38; P = 0.228). Fluid balance was lower with HES than with crystalloids. RAP reduced transfusion requirements compared with crystalloids. Blood loss was comparable between groups.ConclusionsCOPs did not differ between crystalloids and colloids. As a result of increased transcapillary fluid movement, fluid balance was lower with HES than with crystalloids. Haematocrit and transfusion requirements were comparable between groups. However, the latter was lower when RAP was applied to crystalloid priming compared with crystalloids alone. Finally, no differences in blood loss were observed between the groups.
Project description:Using Escherichia coli as a model organism, we studied how water is recruited by a bacterial swarm. A previous analysis of trajectories of small air bubbles revealed a stream of fluid flowing in a clockwise direction ahead of the swarm. A companion study suggested that water moves out of the agar into the swarm in a narrow region centered ∼ 30 μm from the leading edge of the swarm and then back into the agar (at a smaller rate) in a region centered ∼ 120 μm back from the leading edge. Presumably, these flows are driven by changes in osmolarity. Here, we utilized green/red fluorescent liposomes as reporters of osmolarity to verify this hypothesis. The stream of fluid that flows in front of the swarm contains osmolytes. Two distinct regions are observed inside the swarm near its leading edge: an outer high-osmolarity band (∼ 30 mOsm higher than the agar baseline) and an inner low-osmolarity band (isotonic or slightly hypotonic to the agar baseline). This profile supports the fluid-flow model derived from the drift of air bubbles and provides new (to our knowledge) insights into water maintenance in bacterial swarms. High osmotic pressure at the leading edge of the swarm extracts water from the underlying agar and promotes motility. The osmolyte is of high molecular weight and probably is lipopolysaccharide.
Project description:The chemical potential of water () provides an essential thermodynamic characterization of the environment of living organisms, and it is of equal significance as the temperature. For cells, is conventionally expressed in terms of the osmotic pressure (πosm). We have previously suggested that the main contribution to the intracellular πosm of the bacterium E. coli is from soluble negatively-charged proteins and their counter-ions. Here, we expand on this analysis by examining how evolutionary divergent cell types cope with the challenge of maintaining πosm within viable values. Complex organisms, like mammals, maintain constant internal πosm ≈ 0.285 osmol, matching that of 0.154 M NaCl. For bacteria it appears that optimal growth conditions are found for similar or slightly higher πosm (0.25-0.4 osmol), despite that they represent a much earlier stage in evolution. We argue that this value reflects a general adaptation for optimising metabolic function under crowded intracellular conditions. Environmental πosm that differ from this optimum require therefore special measures, as exemplified with gram-positive and gram-negative bacteria. To handle such situations, their membrane encapsulations allow for a compensating turgor pressure that can take both positive and negative values, where positive pressures allow increased frequency of metabolic events through increased intracellular protein concentrations. A remarkable exception to the rule of 0.25-0.4 osmol, is found for halophilic archaea with internal πosm ≈ 15 osmol. The internal organization of these archaea differs in that they utilize a repulsive electrostatic mechanism operating only in the ionic-liquid regime to avoid aggregation, and that they stand out from other organisms by having no turgor pressure.