Serum electrolytes concentrations are usually maintained within a narrow range by complex renal and endocrine homeostatic mechanisms.
Endocrine and renal systems finely tune absorption, distribution and excretion of electrolytes.
Derangements occur when there are
Deficits are due to:
Excesses are due to
For predominantly extracellular electrolytes e.g. Na, serum concentration is a function of total body electrolyte content and total body water content.
Therefore, low sodium concentration may be due to either inadequate sodium or excess water
The degree of symptoms are both a function of the severity of derangement and the rapidity of onset
e.g. chronic renal failure patients can tolerate higher serum potassium levels
see Clinically significant electrolyte disturbances
Serious complications are associated with impairment of:
- laryngospasm/tetany - hypocalcaemia
- hypoventilation - hypoermagnesemia
- Arrhythmias - hypokalaemia/hyperkalaemia, hypermagnesaemia
- Hypotension - hypocalcaemia, hypermagnesaemia, hypophophataemia
- Cerebral oedema - hyponatraemia
- Seizures/Coma - various
NB rapidly treating electrolyte disturbances can also cause complications! In non-life threatening disturbances, slow correction over 48 hours is recommended.