Page 276 - Saunders Comprehensive Review For NCLEX-RN

however, the compensation is more thorough and
selective than that of other regulators, such as the
buffer systems and lungs.
3. During acidosis, the pH decreases and excess
hydrogen ions are secreted into the tubules and
combine with buffers for excretion in the urine.
4. During alkalosis, the pH increases and excess
bicarbonate ions move into the tubules, combine with
sodium, and are excreted in the urine.
5. Selective regulation of bicarbonate occurs in the
kidneys.
a. The kidneys restore bicarbonate by
excreting hydrogen ions and retaining
bicarbonate ions.
b. Excess hydrogen ions are excreted in
the urine in the form of phosphoric
acid.
c. The alteration of certain amino acids in
the renal tubules results in a diffusion
of ammonia into the kidneys; the
ammonia combines with excess
hydrogen ions and is excreted in the
urine.

+
E. Potassium (K )
1. Potassium plays an exchange role in maintaining acid-
base balance.
2. The body changes the potassium level by drawing
hydrogen ions into the cells or by pushing them out
of the cells (potassium movement across cell
membranes is facilitated by transcellular shifting in
response to acid-base patterns).
3. The potassium level changes to compensate for
hydrogen ion level changes (Fig. 9-2).
a. During acidosis, the body protects itself
from the acidic state by moving
hydrogen ions into the cells. Therefore,
potassium moves out to make room for
hydrogen ions and the potassium level
increases.
b. During alkalosis, the cells release
hydrogen ions into the blood in an
attempt to increase the acidity of the
blood; this forces the potassium into
the cells and potassium levels
decrease.

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