Pharmaco-therapeutic group: B05 BB02: Electrolytes with carbohydrates
The solution contains equimolar proportions of sodium and chloride corresponding to half the physiological concentration in the plasma. In addition this solution also contains 5 % (w/v) of carbohydrate in the form of glucose.
Sodium is the primary cation of the extracellular space and together with various anions, regulates the size of this. Sodium and potassium are the major mediators of bioelectric processes within the body.
The sodium content and the liquid metabolism of the body are closely coupled to each other. Each deviation of the plasma sodium concentration from the physiological one simultaneously affects the fluid status of the body.
An increase in the sodium content of the body results also means reduction of the body's free water content independent of the serum osmolality.
Glucose is metabolised ubiquitously as the natural substrate of the cells of the body. Under physiological conditions glucose is the most important energy-supplying carbohydrate with a caloric value of about 16 kJ or 3.75 kcal/g. Nervous tissue, erythrocytes and medulla of the kidneys are amongst the tissues with an obligate requirement for glucose. The concentration of glucose in the blood is reported as 50 – 95 mg/100 ml, or 2.8 – 5.3 mmol/l (fasting).
One the one hand, glucose serves for the synthesis of glycogen as the storage form of carbohydrates and, on the other hand, it is subject to glycolysis to pyruvate and lactate for energy production in the cells. Glucose also serves to maintain the blood sugar level and for the synthesis of important body components. It is primarily insulin, glucagon, glucocorticoids and catecholamines that are involved in the regulation of the blood sugar concentration.
A normal electrolyte and acid-base status is a prerequisite for the optimal utilisation of administered glucose. So an acidosis, in particular, can indicate impairment of the oxidative glucose metabolism.
There are close metabolic relationships between the electrolytes and carbohydrate metabolism; potassium, in particular, is affected. The utilisation of glucose is associated with an increased potassium requirement. Not taking this relationship into account can lead to considerable disturbances of potassium metabolism, which can, amongst other things, lead to massive cardiac arrhythmia.
Glucose utilisation disturbances (glucose intolerance) can occur under conditions of pathological metabolism. These mainly include diabetes mellitus and states of metabolic stress (e.g. intra-, and postoperatively, severe disease, injury), hormonally mediated depression of glucose tolerance, which can even lead to hyperglycaemia without exogenous supply of the substrate. Hyperglycaemia can - depending on its severity - lead to osmotically mediated renal fluid losses with consecutive hypertonic dehydration, to hyperosmotic disorders up to and including hyperosmotic coma.
Excessive glucose administration, particularly in the condition of a postaggression syndrome, can lead to an appreciable aggravation of the impairment of glucose utilisation and, as a result of the limitation of oxidative glucose utilisation, to an increased conversion of glucose into lipids. This in turn can be associated, amongst other things, with an increased carbon dioxide load of the body (problems with weaning from the respirator) and increased fatty infiltration of the tissues, particularly the liver. Patients with skull and brain injury and cerebral oedema are particularly at risk from disturbances of the glucose homeostasis. Here even slight disturbances of the blood glucose concentration and the associated increase in plasma (serum) osmolality can lead to a considerable increase in the degree of cerebral damage.
Appropriate doses (40 ml/kg body weight per day) of this solution can be used to cover the obligatory carbohydrate requirement of the order of 2 g glucose/kg body weight/day (hypocaloric infusion therapy).