A FORMULA AND NOMOGRAM FOR THE ESTIMATION OF THE OSMOTIC PRESSURE OF COLLOIDS FROM THE ALBUMIN AND TOTAL PROTEIN CONCENTRATIONS OF HUMAN BLOOD SERA

Controversies regarding albumin therapy in cirrhosis

Albumin is the most abundant protein in the human body and is synthetized exclusively by the liver. Therefore, serum albumin levels are reduced in acute and/or chronic liver disease. In cirrhosis, low levels of albumin predict the outcome. In advanced cirrhosis, the quality of albumin is decreased due to high oxidative stress and a proinflammatory state. Therefore, the administration of i.v. albumin would seem to be of pathophysiological relevance and benefit. Yet, the questions that remain are who, when, how much, and how often. While albumin infusion is recommended after large-volume paracentesis, at diagnosis of spontaneous bacterial peritonitis, in acute kidney injury, and in hepatorenal syndrome, the amount and schedule of albumin to be administered require refinement, particularly given complications related to volume overload that have become increasingly apparent. Other indications for albumin such as infections other than spontaneous bacterial peritonitis, hyponatremia, HE, prevention of poor outcomes in hospitalized, and in outpatients with cirrhosis are still debated. The results of studies in these settings are either negative, controversial, or inconclusive. This sheds some doubts regarding the use of albumin as a "one size fits all" strategy. The indication and patient selection are crucial and not always intuitive. The amount and frequency also seem to play a role in the success or failure of albumin. This review will critically discuss the evidence and underline areas where there are indications for albumin use and others where evidence is still insufficient and will have to await the development/results of randomized controlled trials.

Potential and limits of a colloid approach to protein solutions

Looking at globular proteins with the eyes of a colloid scientist has a long tradition, in fact a significant part of the early colloid literature was focused on protein solutions. However, it has also been recognized that proteins are much more complex than the typical hard sphere-like synthetic model colloids. Proteins are not perfect spheres, their interaction potentials are in general not isotropic, and using theories developed for such particles are thus clearly inadequate in many cases. In this perspective article, we now take a closer look at the field. In particular, we reflect on the fact that modern colloid science has been undergoing a tremendous development, where a multitude of novel systems have been developed in the lab and in silico. During the last decade we have seen a rapidly increasing number of reports on the synthesis of anisotropic, patchy and/or responsive synthetic colloids, that start to resemble their complex biological counterparts. This experimental development is also reflected in a corresponding theoretical and simulation effort. The experimental and theoretical toolbox of colloid science has thus rapidly expanded, and there is obviously an enormous potential for an application of these new concepts to protein solutions, which has already been realized and harvested in recent years. In this perspective article we make an attempt to critically discuss the exploitation of colloid science concepts to better understand protein solutions. We not only consider classical applications such as the attempt to understand and predict solution stability and phase behaviour, but also discuss new challenges related to the dynamics, flow behaviour and liquid-solid transitions found in concentrated or crowded protein solutions. It not only aims to provide an overview on the progress in experimental and theoretical (bio)colloid science, but also discusses current shortcomings in our ability to correctly reproduce and predict the structural and dynamic properties of protein solutions based on such a colloid approach.

NUTRITIONAL EDEMA IN THE DOG : II. HYPOALBUMINEMIA AND THE AUGMENTATION OF TISSUE FLUID

The manner in which edema develops in dogs maintained on a diet low in protein is described. Pre-edematous fullness of the tissues is observed for some weeks before palpable edema develops. The state of pre-edema does not merge gradually with that of true edema but rather the transition is relatively sudden. Among twenty dogs the time required for the production of edema varied from 35 to 100 days and averaged 61 days. With three animals in which the nitrogen metabolism was studied during the period before edema had developed, the observed loss of weight was consistently less than the theoretical loss of weight calculated from the negative nitrogen balance. Reasons are given for interpreting the discrepancy as evidence of increasing retention of fluid during the stage of pre-edema. In general the weight curve does not rise during the transition from pre-edema to edema. However, the weight does increase rapidly when fluid is accumulating in the peritoneal cavity. The level of serum albumin which is critical for the development of edema varied between 1.04 and 2.17 gm. per cent. The range is sufficiently wide to suggest the existence of other factors of importance in determining the exact time of appearance of edema. During the phase of recovery the level of albumin which is critical for the disappearance of edema may be appreciably higher than the level which was critical for the formation of edema. Among thirty samples of edema fluid the protein concentration was from 0.02 to 0.72 gm. per cent. The average protein level was 0.230 and the median level 0.165 gm. per cent. A positive correlation is not demonstrable between the duration of edema and the protein content of edema fluid. A difference in behavior toward fluid retention between subcutaneous tissue and peritoneal cavity is pointed out. Subcutaneous tissue is more resistant to acute stress and less resistant to prolonged or repeated stress than the peritoneal cavity. The rôle of tissue pressure in the etiology of edema is discussed. It is suggested that the critical level of protein in the serum is the concentration which permits the attainment in the tissue spaces of mechanical pressure great enough to break down the restraining action of the connective tissue boundaries of the spaces.

Serum colloidal osmotic pressure in the development of kwashiorkor and in recovery: its relationship to albumin and globulin concentrations and oedema

1. Serum colloidal osmotic pressure was measured in children 'at risk' to kwashiorkor, in other with frank signs of the disease and during recovery. Simultaneous estimations of serum albumin and globulin concentrations and assessments of the extent of oedema were also made. 2. During the development of kwashiorkor, serum colloidal osmotic pressure did not decrease significantly until albumin concentration was 25-1--27-5 g/l. Above 30-0 g/1, colloidal osmotic pressure was maintained at normal levels during which time a significant reciprocal relationship existed between albumin and globulin concentrations. These findings provide support for suggestions that there may be on oncotic regulation of albumin synthesis. 3. Low albumin concentrations were mainly responsible for the low colloidal osmotic pressures found in children with kwashiorkor and in agreement and previous findings the threshold for the formation of oncotic oedema was found to be about 2-35--2-65 kN/m2. 4. Values for colloidal osmotic pressure calculated from serum albumin and gobulin concentrations using emprical formulas did not agree well with measured values and no constant correction factor suitable over the whole range of albumin concentrations found in rural Ugandan children could be devised. In many hypoalbuminaemic children ony direct measurement of serum colloidal pressure will indicate the true extent of risk to an episode of oedema.

High protein edema due to diffuse abnormality of capillary permeability

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