03_06_02 Common electrolyte disorders - K, Mg PO4

Common Electrolyte Disorders (K, Mg Po4)
Session Overview
Description
This session will discuss the management of critically-ill patients with abnormalities in serum potassium (K+), magnesium (Mg2+) and phosphate (PO42-).

Learning Objectives
By the end of this session you will be able to:

• State the normal ranges for serum potassium (K+), magnesium (Mg2+) and phosphate (PO42-)
• List common causes of hypokalaemia and hyperkalaemia
• Recognize electrocardiograph (ECG) changes caused by hypokalaemia and hyperkalaemia
• Apply management regimens for treating abnormal K+
• List common causes of hypomagnesaemia and hypermagnesaemia
• Recognize the indications for intravenous magnesium
• List the causes of hypophosphataemia and its clinical manifestations

Potassium, magnesium and phosphate are the major ions in the intracellular fluid (ICF).

In health, these ions are absorbed from the diet, and excreted renally. Phosphate and potassium levels are also subject to a degree of hormonal control. Gastrointestinal losses can occur in ill-health.

As intracellular ions, the major content of these ions is in body tissue stores, rather than in the extracellular fluid (ECF) compartments.

Serum levels of these ions do not reflect body stores and vice versa. Ions can shift in and out of cells (redistribution) under various influences. It is the unbound fraction of the ion which is active.

All of these ions are involved in electrical gradients across excitable cell membranes. Changes in the intra- to extracellular ratio of these ions can affect the depolarization of excitable membranes, notably cardiac cells, neuronal cells and muscle.

Consequently, high or low serum levels of these ions can lead to cardiac and neuromuscular symptoms and complications.