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Clinical Anesthesiology, 4e
| Section IV. Physiology, Pathophysiology, & Anesthetic Management > |
Disorders of Potassium Balance
Sections: Disorders of
Potassium Balance, Normal Potassium
Balance, Regulation of
Extracellular Potassium Concentration, Intercompartmental
Shifts of Potassium, Urinary Excretion
of Potassium, Hypokalemia, Hypokalemia
Due to the Intracellular Movement of Potassium, Hypokalemia
Due to Increased Potassium Losses, Hypokalemia
Due to Decreased Potassium Intake, Clinical Manifestations
of Hypokalemia, Treatment of
Hypokalemia, Anesthetic Considerations, Hyperkalemia, Hyperkalemia
Due to Extracellular Movement of Potassium, Hyperkalemia
Due to Decreased Renal Excretion of Potassium, Hyperkalemia
Due to Increased Potassium Intake, Clinical Manifestations
of Hyperkalemia, Treatment of
Hyperkalemia, Anesthetic Considerations.
Topics Discussed: disorder of fluid or electrolyte; hyperkalemia; hypokalemia; potassium; potassium balance; potassium measurement.
Excerpt:
"Potassium plays a major role in the electrophysiology of cell
membranes as well as carbohydrate and protein synthesis (see below).
The resting cell membrane potential is normally dependent on the
ratio of intracellular to extracellular potassium concentrations.
Intracellular potassium concentration is estimated to be 140 mEq/L,
whereas extracellular potassium concentration is normally about
4 mEq/L. Although the regulation of intracellular [K+] is
poorly understood, extracellular [K+] generally
reflects the balance between potassium intake and excretion.Dietary potassium intake averages 80 mEq/d in adults
(range, 40–140 mEq/d). About 70 mEq of that amount
is normally excreted in urine, whereas the remaining 10 mEq is lost
through the gastrointestinal tract.Urinary potassium excretion generally parallels its extracellular
concentration. Potassium is secreted by tubular cells in the distal
nephron. Extracellular [K+] is
a major determinant of aldosterone secretion from the adrenal gland.
Hyperkalemia stimulates aldosterone secretion, whereas hypokalemia
suppresses aldosterone secretion. Renal tubular flow in the distal
nephron may also be an important..."
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