Fluid, Electrolyte and Acid-Base Physiology

Hyperglycemia

Introduction Because hyperglycemia due to poorly controlled diabetes mellitus is a common disorder associated with a number of disturbances in fluid and electrolyte balances, we thought it would be useful to have a separate chapter on hyperglycemia to address these…

Hyperkalemia

Introduction Hyperkalemia is usually defined as a concentration of potassium ions (K + ) in plasma (P K ) that is greater than 5 mmol Hyperkalemia is a common electrolyte disorder that may be present in a number of disease…

Hypokalemia

Introduction Hypokalemia, usually defined as a concentration of potassium (K + ) ions in plasma (P K ) of less than 3.5 mmol/L, is a common electrolyte disorder both in the outpatient and the inpatient setting. When faced with a…

Potassium Physiology

Introduction Regulation of total body potassium (K + ) ion homeostasis is vital for survival. Changes in the concentration of K + ions in plasma (P K ) are associated with changes in the negative voltage across cell membranes and…

Polyuria

Introduction Polyuria is caused by either a water diuresis or an osmotic diuresis. Many patients who present with polyuria also have hypernatremia because they excrete a large volume of urine with a low concentration of sodium (Na + ) plus…

Hypernatremia

Introduction Hypernatremia is defined as a concentration of sodium (Na + ) ions in plasma (P Na ) that is greater than 145 mmol Hypernatremia is not a diagnosis; rather it is a laboratory finding that may be the result…

Hyponatremia

Introduction Hyponatremia is defined as a concentration of sodium (Na + ) ions in plasma (P Na ) that is less than 135 mmol Hyponatremia is the most common electrolyte disorder encountered in clinical practice. It can be associated with…

Sodium and Water Physiology

Introduction It is important to understand the physiology of sodium (Na + ) and of water homeostasis to determine the pathophysiology that leads to alteration in the extracellular fluid (ECF) volume and/or the concentration of sodium ions (Na + )…

Respiratory Acid–Base Disturbances

Introduction Respiratory acidosis is characterized by an increased arterial blood PCO 2 and H + ion concentration. The major cause of respiratory acidosis is alveolar hypoventilation. The expected physiologic response is an increased PHCO3 P HCO 3 . The increase…

Metabolic Alkalosis

Introduction Metabolic alkalosis is principally an electrolyte disorder that is accompanied by changes in acid–base parameters in plasma, namely an elevated concentration of bicarbonate ( HCO3− HCO 3 − ) ions ( PHCO3 P HCO 3 ) and elevated pH.…