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404 Chapter 12

Hyponatremia. Hyponatremia is a more common form of sodium abnormality than
Hyponatremia is com-
monly related to ECF deficits hypernatremia. It is commonly related to ECF deficit (hypovolemia). The usual
(hypovolemia). The usual treatment is replenishment of sodium with saline solution (100 to 300 mL of 2.5%
treatment is replenishment of
sodium with saline solution. or 3% saline). It is not safe to administer fluids that have no sodium because water
intoxication may occur. Rapid movement of sodium-free fluid into the brain cells
and kidney cells by the action of osmosis may cause edema and shutdown of these
organs (Eggleston, 1985).
Hypernatremia. Hypernatremia is an uncommon problem in the clinical setting.
Hypernatremia is an
uncommon problem and it When hypernatremia occurs, it is usually related to water deficit as a result of pro-
is usually related to water longed intravenous fluid administration with sufficient sodium but no dextrose.
deficit as a result of prolonged
intravenous fluid administra- This condition is readily reversible by a water solution supplemented with dextrose
tion with sufficient sodium (Eggleston, 1985).
but no dextrose.
Potassium Abnormalities

Potassium is the major cation in the intracellular fluid (ICF), therefore it has a nar-
row normal range (3–5 mEq/L) outside the cells. The potassium concentration in
the ECF may be higher than normal (hyperkalemia) or lower than normal (hypo-
kalemia). The clinical signs of potassium abnormality are outlined in Table 12-16.
1
Hypokalemia. Hypokalemia is a more common form of potassium (K ) abnormality
Potassium deficiency may than hyperkalemia. Potassium deficiency may be caused by excessive K loss (e.g.,
1
1
be caused by excessive K
1
loss (trauma, severe infection, trauma, severe infection, vomiting, use of diuretics) or inadequate K intake (e.g.,
vomiting, use of diuretics) or massive or prolonged intravenous fluid infusion without supplemental potassium).
1
inadequate K intake (mas-
sive or prolonged intravenous Normal breakdown of body tissue produces some potassium as a by-product, but
fluid infusion without supple-
mental potassium). hypokalemia may still occur if excretion exceeds production.
Deficiency of serum potassium may be corrected by oral intake or slow intrave-
nous infusion of potassium chloride. Potassium chloride is used because hypochlo-
remia (low chloride) usually coexists with hypokalemia and the chloride ions must
be replaced at the same time.

TABLE 12-16 Clinical Signs of Potassium Abnormality

System Hypokalemia Hyperkalemia
Neuromuscular Decreased muscle functions Increased neuromuscular conduction

Cardiac Flattened T wave and depressed Elevated T wave and depressed ST
ST segment on ECG segment on ECG (mild)
Arrhythmias Cardiac arrest (severe)

Gastrointestinal Decreased bowel activity Increased bowel activity
Diminished or absent bowel Diarrhea
sounds
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