The document discusses acid-base balance and regulation in the human body. It states that the body maintains a steady balance between acids and bases through three main mechanisms: buffer systems, the respiratory system, and the renal system. People with conditions like diabetes, COPD, kidney disease, or the elderly are most at risk of acid-base imbalances. The buffer systems act quickly to neutralize acids and maintain blood pH, while the respiratory system removes carbon dioxide and the renal system filters and regulates bicarbonate and acid levels in the blood and urine to further support acid-base balance.

1. Acid- base balance
www.tastafe.tas.edu.au
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2. Introduction
• The body normally maintains a steady
balance between acids produced during
metabolism and bases that neutralise and
promote the excretion of the acids
•
Brown & Edwards 2012 (p.368)
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3. Acid-base Imbalance – who is
at risk?
• People who live with diabetes mellitus,
chronic obstructive pulmonary disease
(COPD) and kidney disease frequently
develop acid – base imbalances
•
Brown & Edwards 2012 (p.368)
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5. Acid-base Imbalance – who is at
risk?
• People experiencing vomiting and
diarrhoea can lose acids and bases in
addition to loss of fluids and electrolytes
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6. Acid-base Imbalance – who is at
risk?
• Any patient with a serious illness is at risk
of acid-base imbalance
•
Brown & Edwards 2012 (p.368)
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7. Acid-base Imbalance – who is at
risk?
• The older adult is at risk - their kidneys
and lungs do not compensate so well
anymore for acid-base imbalance
•
Brown & Edwards 2012 (p.368)
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8. pH and Hydrogen ion Concentration
• The acidity or alkalinity of a solution
depends upon its hydrogen (H+) ion
concentration
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9. pH and Hydrogen ion Concentration
• An increase in H+ concentration leads
to acidity
• A decrease in H+ concentration leads
to alkalinity
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10. pH and Hydrogen ion Concentration
• Despite the fact that acids are produced in
the body everyday , the hydrogen ion
concentration of body fluids is small
(0.0004mmol/L
• This tiny amount is maintained within a
narrow range to ensure optimum cellular
function
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11. pH and Hydrogen ion
Concentration
• Hydrogen ion concentration is usually
expressed as pH
• The lower the pH the higher the H+
concentration
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12. pH and Hydrogen ion Concentration
• The pH of a chemical solution may range
from 1-14
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13. pH and Hydrogen ion Concentration
• An acid solution has a pH of less than (<)
7
• An alkaline solution has a pH of greater
than (>) 7
• A neutral solution has a pH of 7
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14. pH and Hydrogen ion Concentration
• Blood is slightly alkaline (pH 7.35 –
7.45)
• If the pH of blood drops below 7.35 the
person is said to have acidosis
• If the pH of blood is greater than 7.45 the
person has alkalosis
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15. pH and Hydrogen ion Concentration
• Relative to a pH of 7, a pH of 8 represents
a 10-fold decrease in H+ concentration
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16. Acid-base Regulation
• The body’s metabolic processes are
constantly producing acids
• These acids must be neutralised and
excreted to maintain acid-base balance
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17. Acid-base Regulation
• Normally the body has three (3) mechanisms by
which it regulates acid-base balance to maintain
the arterial pH between 7.35 – 7.45
•
•
•
•
These mechanisms are:
The buffer systems
The respiratory system
The renal system
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18. The Buffer Systems
• The buffer systems are the fastest acting
systems and are the primary regulators of
acid-base balance.
• Buffers act chemically to change strong
acids into weaker acids or to bind acids to
neutralise their effects
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19. What is a Buffer?
• A buffer consists of a weakly ionised acid
or base and its salt that functions to
minimise the effects of acids on blood pH
until they can be excreted from the body
• Buffers alone cannot maintain blood pH
and they need an adequately functioning
respiratory and renal system
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20. The Respiratory System
• Lungs help maintain a normal pH by
excreting CO2 and water which are byproducts of cellular metabolism
• The rate of C02 excretion is controlled by
the respiratory centre in the medulla in the
brainstem
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21. The Respiratory System
• If increased C02 or H+ are detected the
respiratory centre stimulates an increased
rate and depth of breathing
• Respiratory rate and depth are inhibited if
the centre detects low H+ or C02 levels
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22. The Respiratory System
• If a respiratory condition is the cause of an
acid base imbalance (respiratory failure,
for example) the respiratory system loses
its ability to correct a pH alteration
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23. The Renal System
• Under normal circumstances the kidneys
reabsorb and conserve all of the
bicarbonate they filter.
• The kidneys can also generate more
bicarbonate and eliminate excess H+ to
compensate for acidosis
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24. The Renal System
• The kidneys usually excrete acidic urine
(average pH6)
• If the renal system is the cause of an acidbase imbalance (renal failure, for example)
it loses its ability to correct an acid-base
imbalance
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25. Reference
• Brown, D. & Edwards, H. (2012) Lewis’s
Medical Surgical Nursing: Assessment
and Management of Clinical Problems,
Mosby Elsevier, Sydney, Australia
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