03_06_01 Common electrolyte disorders - Na

Common electrolyte disorders - Na
Session Overview
Description
This session will discuss the pathophysiology, clinical features and management of both hyponatraemia and hypernatraemia in critically-ill patients.

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

• State the normal range for serum sodium in mmol/L
• Estimate plasma osmolality from simple blood tests
• Classify causes of hyponatraemia and hypernatraemia
• List common causes of the syndrome of inappropriate antidiuretic hormone secretion
• Select appropriate tests for investigating patients with hyponatraemia and hypernatraemia

Prerequisites
Before commencing this session you should complete sessions:

• Regulation of Electrolyte and Acid-Base Balance 1 (001-0657)
• Regulation of Electrolyte and Acid-Base Balance 2 (001-0658)
• Investigations and Interpretation/Biochemistry - Hyper/hyponatraemia (001-0155)

Sodium is the major extracellular cation and therefore the main determinant of plasma osmolality. In health, sodium concentration and plasma osmolality are tightly regulated.

Sodium concentration is dependent upon the relative amounts of sodium and water in the extracellular fluid (ECF). Abnormal sodium concentrations can occur with different ECF volumes.

Assessment of the patient’s volume status is essential for differential diagnosis and management.

Many patients are admitted with, or subsequently develop, sodium abnormalities. Multiple pathologies, IV infusions, drug treatments and the stress response to critical illness can all contribute.

As many of the underlying factors are predictable or potentially avoidable, the incidence of acquired hyponatraemia and hypernatraemia may be used as a 'quality indicator' of ICU care.