Electrolytes are chemicals in the body that help to regulate normal functioning. Like acid-base balance, these elements also need to be kept in balance or the body may experience disease.
Although there are many trace elements that keep the body healthy, several important electrolytes can severely affect patients when they are either too high (hyper…) or too low (hypo…). Understanding what each electrolyte does, what happens when there isn’t enough, and what happens when there is too much, is essential knowledge for nurses and can help guide electrolyte therapy.
Sodium, or Na, is one of the most important electrolytes in the body and is responsible for a number of important functions, mostly related to fluid and water regulation. The normal accepted range for sodium is 134 to 145 mEq/L.
Hyponatraemia is considered to be a serum sodium below 134 mEq/L. A common cause of hyponatraemia is water retention due to cardiac or renal or hepatic failure. Other causes of hyponatraemia include some medicines, psychogenic polydipsia (excessive water intake) and syndrome of inappropriate ADH (antidiuretic hormone) secretion, and chronic or severe vomiting and diarrhoea.
Common symptoms of hyponatraemia include confusion, agitation, nausea and vomiting, muscle weakness, spasms or cramps.
Hypernatraemia is defined as a serum sodium greater than 145 mEq/L. Causes of hypernatraemia can be thought of simply as anything that leads to excessive water loss or salt gain. For example, water depletion or dehydration may be caused by vomiting or diarrhoea. Excessive ingestion of sodium is rare, but the administration of infusions containing sodium such as sodium chloride or sodium bicarbonate may lead to hypernatraemia.
Clinical features of hypernatraemia may include fever, irritability, drowsiness, irritability, lethargy and confusion.
Potassium, or K, is responsible for the functioning of excitable tissues such as skeletal and cardiac muscle and nerves. The normal range for potassium is 3.5 to 5.0 mmol/L.
Hypokalaemia is defined as a serum potassium less than 3.5 mmol/L. A low serum potassium may be caused by decreased oral intake, increased renal or gastrointestinal loss of potassium, or a shift of potassium within the body’s fluid compartments (from outside the cell where it should be, to inside the cell).
Common clinical features of hypokalaemia range from muscle weakness and ileus (lack of peristalsis), to serious cardiac arrhythmias such as ventricular tachycardias.
Hyperkalaemia, a serum potassium greater than 5.0 mmol/L, may be caused by excessive intake, tissue damage from burns or trauma, medicines such as potassium sparing diuretics, and most commonly, due to renal failure.
Clinical signs of hyperkalaemia include muscle weakness, hypotension, bradycardia and loss of cardiac output, and ECG changes may include peaked T waves and flattened P waves.
Magnesium, or Mg, is another element that has a strong effect on muscle contractions. The normal plasma range for magnesium is 0.70 to 0.95 mmol/L.
Hypomagnesaemia, or a decreased plasma magnesium level, may be caused by decreased intake or increased loss of magnesium. Clinical signs include confusion, irritability, delirium, muscle tremors and tachyarrhythmias.
Hypermagnesaemia is when the level of magnesium in the blood is above the normal range. Fortunately, this is uncommon. Symptoms include poor reflexes, low blood pressure, respiratory depression, and cardiac arrest. This is usually caused by the excessive administration of magnesium and lithium therapy, often in the presence of renal failure.
Calcium, or Ca, is an important element in the body as it helps to control nerve impulses, muscle contractions and has a role in clotting. The serum calcium range should be between 2.20 to 2.55 mmol/L when normal.
Hypocalcaemia, the presence of low serum calcium levels in the blood, is relatively rare because the bones always act as a reservoir for this electrolyte. However, parathyroid disease, vitamin D deficiency, septic shock and acute pancreatitis can cause this problem. Some symptoms include tetany (involuntary muscle contraction), mental changes and decreased cardiac output.
Hypercalcaemia, elevated levels of calcium in the blood, again arises from parathyroid problems and vitamin D issues. Signs of this form of electrolyte imbalance include nausea, vomiting, polyuria, muscular weakness and mental disturbance.
Phosphate, or P, is an electrolyte used in several functions throughout the body. Although a phosphate imbalance isn’t as well known as some of the other imbalances, it can still cause problems with your patient’s condition. The normal range of phosphate in the plasma is generally between 0.8 to 1.3 mmol/L. The signs and symptoms of either abnormal reading are usually subtle.
For hypophosphataemia, when levels of phosphate in the blood are below the normal range, the symptoms generally include muscle weakness, heart failure, seizure, and coma. It may be caused by vitamin D deficiency, hyperparathyroidism, or alcoholism. Hypophosphataemia may also be present, in addition to other electrolyte disturbances, in re-feeding syndrome, which is associated with the commencement of total parental nutrition (TPN).
Hyperphosphataemia, when levels of phosphate in the blood are above the normal range, can be caused by kidney disease, parathyroid issues, and metabolic or respiratory acidosis. Symptoms are usually not present, and they are related to hypocalcaemia. Renal patients can experience hardened calcium deposits when this condition goes untreated.
- Delaney, A & Finfer, S 2014, ‘Fluid and Electrolyte Therapy’, in A Bersten & N Soni (eds), OH’s Intensive Care Manual, 7th edn, Butterworth-Heinemann, Oxford.
- Fulop, T, Agraharkar, M, Fahlen, MT & Workeneh, BT 2014, Hypermagnesemia, Medscape, New York, NY, USA, viewed 28 September 2016, http://emedicine.medscape.com/article/246489-overview
- Mayo Clinic Staff 2014, ‘Causes’, Diseases and Conditions: Hyponatremia, Mayo Foundation for Medical Education and Research, USA, viewed 28 September 2016, http://www.mayoclinic.org/diseases-conditions/hyponatremia/basics/causes/con-20031445