KEY POINTS

1. Water is the major component of all fluid compartments within the body and represents approximately 60% of body weight.
2. Sodium is the most abundant positive ion of the ECF compartment and is critical in determining the extracellular and intracellular osmolality.
3. Potassium is the most abundant positive ion in the intracellular fluid and plays an important role in the membrane potential of cells.
4. Calcium is the key component that mediates muscle contraction; exocrine, endocrine, and neurocrine secretion; cell growth; and the transport and secretion of fluids and electrolytes.
5. Magnesium is essential for many biochemical reactions; its pharmacologic properties have only recently been appreciated.
6. Phosphate stores and releases energy through high-energy phosphate bonds and is integral to the structure of proteins, lipids, and bone.
7. Chloride is the predominant anion in the ECF.
8. Glucose is a crucial fuel source, and insulin facilitates glucose movement into cells in a process that also requires potassium and phosphate.
9. Diabetes affects multiple organ systems, and the perioperative effect of diabetes can be profound.
10. The most common causes of metabolic alkalosis are antacid therapy, incidental administration of citrate with blood products, sodium bicarbonate administration, gastric drainage, and renal bicarbonate retention.
11. Metabolic acidosis is commonly caused by low cardiac output and end-stage liver disease.
12. Transfusion of blood products improves tissue oxygenation and decreases bleeding, but it also increases the risk of transmission of infectious diseases, transfusion reactions, immunosuppression, and alloimmunization.
13. Anesthetics may blunt the normal physiologic responses to hypovolemia and the stress response.
14. Shock is dysfunction of intracellular processes caused by the lack of energy.