Acid-Base Imbalance: Understanding Disorders in Acid-Base Balance

University of Gondar
College of medicine and health science
department of anesthesia
Misganaw M
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Acid- Base Imbalance

INTRODUCTION
 Disorders in acid-base balance are commonly
found in critically ill patients.
 Clinicians responsible for these patients need a clear
understanding of acid-base pathophysiology in order to
provide effective treatment for these disorders
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INTRODUCTION
Definition:
 pH is defined as potential of H+ Ion concentration in
body fluid and acid- base balance is:
 Balance of H conc. In extracellular fluid (ECF) .
 To Achieve Homeostasis .
 Balance Between:
 H+ is produced as a by-product of metabolism
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INTRODUCTION
The body maintains a narrow pH range by 3 mechanisms:
1. Chemical buffers (extracellular and intracellular)
react instantly to compensate for the addition or
subtraction of H+ ions.
2. CO2 elimination is controlled by the lungs
(respiratory system). Decreases (increases) in pH result
in decreases (increases) in PCO2 within minutes.
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3. HCO3- elimination is controlled by the kidneys.
 Decreases (increases) in pH result in increases
(decreases) in HCO3-.
 It takes hours to days for the renal system to compensate
for changes in pH
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INTRODUCTION
 The three different buffering systems are:
1) Respiratory buffering system
• Uses bicarbonate
2) Blood buffering system
• Uses bicarbonate, phosphate, and protein
3) Renal buffering system
• Uses bicarbonate, phosphate, and ammonia
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INTRODUCTION
 A normal [H+] of 40 nEq/L corresponds to a pH of
7.40.
 Because the pH is a negative logarithm of the [H+],
changes in pH are inversely related to changes in [H+]
(e.g., a decrease in pH is associated with an increase
in [H+])
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ACID-BASE DISORDERS
 Types of Acid-Base Disorders
 . A respiratory acid-base disorder is a change in [H+] that is a
direct result of a change in PCO2, an increase in PCO2 will
increase the [H+] and produce a respiratory acidosis, while a
decrease in PCO2 will decrease the [H+] and produce a
respiratory alkalosis.
 . A metabolic acid-base disorder is a change in [H+] that is a
direct result of a change in HCO3.
 an increase in HCO3 will decrease the [H+] and produce a
metabolic alkalosis, while a decrease in HCO3 will
increase the [H+] and produce a metabolic acidosis.
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