The clinical significance of hypoalbuminaemia

Albumin is a relatively small molecule with a radius of 7.5 nm and a molecular weight of 65 kDa. It is the most abundant protein in plasma, accounting for 60-75% of its oncotic pressure. Its concentration in plasma is merely one static measurement reflecting a dynamic and complex system of albumin physiology, and is the net result of several different processes, one or more of which may become deranged by disease or its treatment. It is also unsurprising that hypoalbuminaemia has proved to be an indicator of morbidity and mortality risk since the underlying conditions which cause it, including protein energy malnutrition, crystalloid overload, inflammation, and liver dysfunction are themselves risk factors. In some cases, its underlying cause may require treatment but mostly it is just a parameter to be monitored and used as one measure of clinical progress or deterioration. While malnutrition, associated with a low protein intake, may be a contributory cause of hypoalbuminaemia, in the absence of inflammation and/or dilution with crystalloid its development in response to malnutrition alone is slow compared with the rapid change caused by inflammatory redistribution or dilution with crystalloids. Other significant causes include liver dysfunction and serous losses. These causal factors may occur singly or in combination in any particular case. Treatment is that of the underlying causes and associated conditions such as a low plasma volume, not of hypoalbuminaemia per se.