Chapter outlines
| POTASSIUM |
| Physiological Basis |
| Potassium Homeostasis |
| Regulation of Serum Potassium |
| Correlation of Serum and Body Potassium |
| HYPOKALEMIA |
| Etiology |
| Clinical Features and ECG Changes |
| Diagnosis |
| History and physical examination |
| Laboratory evaluation |
| Additional diagnostic tests |
| - Urinary potassium excretion |
| - Acid-base status |
| Management |
| Goals |
| Prevention |
| Replenishment of potassium deficit |
| - Estimation of the potassium deficit |
| - Selection of treatment modality |
| - Precautions |
| - How much and how long |
| Oral potassium supplementation |
| Intravenous potassium supplementation |
| - Selection of formulations |
| - Potassium containing IV fluids |
| - Indications |
| - Recommendations for administration |
| - Special considerations |
| The target of K+ supplementation |
| Correction of the underlying causes |
POTASSIUM
PHYSIOLOGICAL BASIS
Potassium (K+) is a major intracellular cation and the second most abundant cation in the body (next to cation sodium). Total body potassium is about 3,500 mEq. Out of this, 98% of potassium is intracellular, and just 2% of potassium is extracellular. Thus, the normal serum potassium concentration is 3.5 to 5.0 mEq/L vs. an intracellular 140 to 150 mEq/L.
Potassium plays a crucial role in the following:
- Normal functioning of cells: Synthesis of DNA and protein, cell division and growth, enzyme function.
- Neuromuscular transmission: Maintaining cell membrane potential, cellular excitability, conduction of nerve impulses which help in maintaining skeletal, cardiac, and smooth muscle cell contraction.
- Regulate intracellular osmolality and cell volume.
- Maintain acid-base balance and regulate intracellular pH.
POTASSIUM HOMEOSTASIS
The average potassium intake is about 77 and 59 mEq per day in adult men and women, respectively [1]. 90% of potassium consumed is absorbed in the upper gastrointestinal (GI) tract, out of which kidneys excrete 90%, and the remaining 10% is excreted in the stool.
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