Rehydration (fluid replacement): in more severe cases of dehydration, in the form of parenteral rehydration (infusions) – based on an estimate of water loss (following example: adult, 70 kg) and on symptoms:
In case of exsiccosis (dehydration), do not administer plasma expanders (colloidal (“very finely divided”) solutions whose osmotic pressure is greater than that of blood plasma)! They would increase the extravascular (located outside the blood vessel) fluid deficit.
Cautious water substitution in cardiac or renal insufficiency (heart or kidney failure) → control CVD and body weight (pulmonary edema (water retention in the lungs)!).
Slight deviations of serum sodium from the norm (125-150 mmol/l) usually do not yet cause symptoms. Nevertheless, the triggering cause must be eliminated (e.g., discontinuation of diuretic therapy).
Isotonic dehydration
Supply of isotonic or isoionic fluid (e.g., Ringer’s solution: isotonic electrolyte solution for intravenous infusion).
Cave: If hyponatremia (excessively low bloodsodium levels) persists for a prolonged period (> 48 hours), cerebrospinal fluid (CSF (“nerve fluid”) changes may occur. These must be compensated only slowly, otherwise life-threatening osmotic gradients between CSF and extracellular fluid may occur! The consequence may be brain cell dehydration with demyelination → central pontine myelinolysis (delirium (confusion), dysarthria (speech disorder), dysphagia (swallowing disorder), paraplegia (paraplegia), quadriplegia (paraplegia of all four limbs))Rule of thumb: The total increase in serum sodium should not exceed 6 mmol/l in 24 hours. Serum sodium should be raised to a maximum of 125-130 mmol/l.
Hypertonic dehydration
Supply of osmotically free water (5% glucose solution; after metabolization (metabolization) of glucose, only free water remains) and replacement of one-third of the fluid deficit with isotonic or isoionic electrolyte fluid.
Caveat: In chronic hypernatremia (excessively high blood sodium levels over a period of at least 4 days), the brain has adapted to hyperosmolality in the extracellular space. Correcting this too quickly can lead to cerebral hyperhydration with cerebral edema (brain swelling). Rule of thumb: normalize sodium concentration by about 0.5 mmol/l/hour over a period of 48 hours.
In case of pronounced desiccosis (dehydration): infusion of an isotonic electrolyte solution.