Page 274 - Saunders Comprehensive Review For NCLEX-RN

acid or base is released into the system, and buffers
absorb or release hydrogen ions as needed.
4. Buffers serve as a transport mechanism that carries
excess hydrogen ions to the lungs.
5. Once the primary buffer systems react, they are
consumed, leaving the body less able to withstand
further stress until the buffers are replaced.

The underlying cause of an acid-base imbalance needs to be

identified and the cause needs to be treated to resolve the imbalance.
B. Primary buffer systems in extracellular fluid
1. Hemoglobin system
a. System maintains acid-base balance by
a process called chloride shift.
b. Chloride shifts in and out of the cells in
response to the level of oxygen (O ) in
2
the blood.
c. For each chloride ion that leaves a red
blood cell, a bicarbonate ion enters.
d. For each chloride ion that enters a red
blood cell, a bicarbonate ion leaves.
2. Plasma protein system
a. The system functions along with the
liver to vary the amount of hydrogen
ions in the chemical structure of
plasma proteins.
b. Plasma proteins have the ability to
attract or release hydrogen ions.

3. Carbonic acid–bicarbonate system

a. Primary buffer system in the body
b. The system maintains a pH of 7.4 with a
ratio of 20 parts bicarbonate ( ) to 1
part carbonic acid (H CO ) (Fig. 9-1).
3
2
c. This ratio (20:1) determines the
hydrogen ion concentration of body
fluid.
d. Carbonic acid concentration is
controlled by the excretion of CO by
2
the lungs; the rate and depth of
respiration change in response to
changes in the CO .
2
e. The kidneys control the bicarbonate
concentration and selectively retain or
excrete bicarbonate in response to
bodily needs.

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