Essentials of Anatomy and Physiology

Fluid–Electrolyte and Acid–Base Balance 447

BOX19–2 ELECTROLYTE IMBALANCES

Hyperkalemia—a consequence of acute renal fail-

ure or Addison’s disease. Characterized by weak-

ness, abnormal sensations, cardiac arrhythmias, and

possible cardiac arrest.

IMBALANCES OF CALCIUM

Hypocalcemia—a consequence of hypoparathy-

roidism or decreased calcium intake. Characterized

by muscle spasms leading to tetany.

Hypercalcemia—a consequence of hyperparathy-

roidism. Characterized by muscle weakness, bone

fragility, and possible kidney stones.

IMBALANCES OF SODIUM

Hyponatremia—a consequence of excessive

sweating, diarrhea, or vomiting. Characterized by

dizziness, confusion, weakness, low BP, shock.

Hypernatremia—a consequence of excessive

water loss or sodium ingestion. Characterized by

loss of ICF and extreme thirst and agitation.

IMBALANCES OF POTASSIUM

Hypokalemia—a consequence of vomiting, diar-

rhea, or kidney disease. Characterized by fatigue,

confusion, possible cardiac failure.

Table 19–2 MAJOR ELECTROLYTES

Plasma Level ICF Level

Electrolyte mEq/L* mEq/L Functions

Sodium (Na)

Potassium (K)

Calcium (Ca^2 )

Magnesium (Mg^2 )

Chloride (CI)

Bicarbonate (HCO 3 )

Phosphate (HPO 4 ^2 )

Sulfate (SO 4 ^2 )

*The concentration of an ion is often expressed in milliequivalents per liter, abbreviated mEq/L, which is the number of electrical

charges in each liter of solution.

136–142

3.8–5.0

4.6–5.5

1.3–2.1

95–103

28

1.7–2.6

1

10

141

1

58

4

10

75

2

• Creates much of the osmotic pressure of ECF; the most
  abundant cation in ECF


• Essential for electrical activity of neurons and muscle cells


• Creates much of the osmotic pressure in ICF; the most
  abundant cation in ICF


• Essential for electrical activity of neurons and muscle cells


• Most (98%) is found in bones and teeth


• Maintains normal excitability of neurons and muscle cells


• Essential for blood clotting


• Most (50%) is found in bone


• More abundant in ICF than in ECF


• Essential for ATP production and activity of neurons and
  muscle cells


• Most abundant anion in ECF; diffuses easily into and out
  of cells; helps regulate osmotic pressure


• Part of HCI in gastric juice


• Part of the bicarbonate buffer system


• Most (85%) is found in bones and teeth


• Primarily an ICF anion


• Part of DNA, RNA, ATP, phospholipids


• Part of phosphate buffer system


• Part of some amino acids and proteins