Multidimensional Care II Exam 2
Study Guide 2022/2023
*
Chapter 12 – Assessment and Care of Patients with Problems of Acid-Base Balance
● ABG ranges and analysis
o Normal Ranges:
▪ pH: 7.35-7.45 7.35-7.4= acidosis 7.4-7.45= alkalosis
▪ PaCO2: 35-45
▪ HCO3: 22-26
▪ PaO2: 80-100
o Abnormal Ranges:
▪ Acidosis
● pH: ↓ 7.35
● PaCO2: ↑ 45
● HCO3: ↓ 22
▪ Alkalosis
● pH: ↑ 7.45
● PaCO2: ↓ 35
● HCO3: ↑ 26
▪ PaO2 is abnormal when it is ↓ 80
o How to solve ABG imbalances:
▪ First, look at pH- determine if it is acidic, alkaline, or normal
● If in normal range - determine if the pH is more acidic (7.35-7.4),
or alkaline (7.4-7.45)- this will help us determine compensation
▪ Next, look at PaCO2- determine if it is below 35 (or more alkaline), in
normal range, or above 45 (or more acidic).
▪ Then, look at the HCO3- determine if it is below 22 (or acidic), in normal range,
or above 26 (or alkaline).
▪ Once all readings have been determined, use the ROME method to determine
the ABG imbalance.
, ●Respiratory Opposite- the pH and CO2 levels will be in opposite
directions, Metabolic Equal- the Ph and HCO3 levels will be in the
same or equal direction.
▪ Next look at the PaO2. In our respiratory clients, we must look at this to
determine if there is enough oxygen getting into the lungs or not. If it is lower
than 80, then we know there is not enough perfusion of oxygen within the
arterial blood and that there is breathing difficulty somewhere.
▪ Then we must determine if the patient is fully compensated, partially
compensated, or uncompensated.
● Fully Compensated vs. Partially Compensated vs. Uncompensated
o Compensation occurs when there is an acid base imbalance and the body attempts
to correct an abnormality within the other body system.
▪ First the pH will be affected due to being a buffer. Must look to see if it
is normal, abnormal, acidic, alkaline.
▪ Then we will look at PaCO2 and HCO3. Whichever value is abnormal, that
is your compensation.
o Fully Compensated: The body has placed the pH back to normal. However, there will
be other systems with abnormal ranges. The abnormal value is the body systems that are
compensating. pH normal and HCO3 and PaCO2 are both abnormal. 7.37, 60, 18
o Partially Compensated: The body is compensating for the pH and for both the PaCO2
and HCO3. This places all 3 levels abnormal. This shows that the respiratory and kidneys
are compensating to get the pH back to normal. 7.3, 50, 18
o Uncompensated: The body is not in a state of compensation yet, so there is an
abnormality of the pH and either the PaCO2 or HCO3, but not both. 7.3, 60,
24
● Buffers
o Chemical (bicarbonate and intracellular fluid) and protein buffers (albumin
and globulins)
▪ First line of defense
● Either bind or release hydrogen ions as needed
● Respond quickly to changes in pH
o Respiratory buffers
▪ Second line of defense
● Control the level of hydrogen ions (within minutes) in the blood
through the control of CO2 levels
● When a chemoreceptor senses a change in the level of CO2, a signal
is sent to the brain to alter the rate and depth of respirations.
o Hyperventilation: Decrease in hydrogen ions (helps to blow
off excess hydrogen ions), decreased PaCO2. Central
chemoreceptors inhibited.
o Hypoventilation: Increase in hydrogen ions, increased
PaCO2. Central chemoreceptors stimulated.
o Kidney buffers
▪ Kidneys are the third line of defense.
, ● This buffering system is much slOwer tO respOnd (24-48 hOurs), but it
is the mOst effective buffering system with the lOngest duration.
(kidney mOvement Of bicarbOnate, fOrmation of acids [HPO4 -1 +
H+ → H2PO4 2-], and fOrmation of ammOnium [NH3+ + H+ →
NH4+])
● Kidneys control the movement of bicarbonate in the urine. Bicarbonate
can be reabsorbed into the bloodstream or excreted in the urine in
response to blood levels of hydrogen.
● Kidneys can also produce more bicarbonate when needed.
o High hydrogen ions: Bicarbonate reabsorption and production
o Low hydrogen ions: Bicarbonate excretion
● pH Regulation
o The pH is the expression of the balance between carbon dioxide (CO2), which is
regulated by the lungs, and bicarbonate (HCO 3-), a base regulated by the kidneys. The
greater the concentration of hydrogen, the more acidic the body fluids and the lower
the pH. The lower the concentration of hydrogen, the more alkaline the body fluids and
the higher the pH.
o Example:
o When excess carbon dioxide is produced, the equation shifts to the right, causing
an increase in hydrogen ions (and a decrease in pH).
▪ Whenever the CO2 level changes, the pH changes to the same degree, in
the opposite direction
▪ When the CO2 level of a liquid increases, the pH drops, indicating more
free hydrogen ions (more acidic)
▪ When the CO2 level of a liquid decreases, the pH rises, indicating fewer
free hydrogen ions (more alkaline).
● Causes of imbalances and treatment
o Respiratory Acidosis
▪ What is it:
● pH lower than 7.35
● PaCO2 greater than 45
● HCO3 normal range (unless partially compensated)
● PaO2 less than 80
● The patient may have CO2 retention, increase H+ ions, causing the
pH and CO2 levels to be more acidic. CO2 is an acid in the body
▪ Causes
● Hypoventilation
● COPD
● Asthma
● Pneumonia
Study Guide 2022/2023
*
Chapter 12 – Assessment and Care of Patients with Problems of Acid-Base Balance
● ABG ranges and analysis
o Normal Ranges:
▪ pH: 7.35-7.45 7.35-7.4= acidosis 7.4-7.45= alkalosis
▪ PaCO2: 35-45
▪ HCO3: 22-26
▪ PaO2: 80-100
o Abnormal Ranges:
▪ Acidosis
● pH: ↓ 7.35
● PaCO2: ↑ 45
● HCO3: ↓ 22
▪ Alkalosis
● pH: ↑ 7.45
● PaCO2: ↓ 35
● HCO3: ↑ 26
▪ PaO2 is abnormal when it is ↓ 80
o How to solve ABG imbalances:
▪ First, look at pH- determine if it is acidic, alkaline, or normal
● If in normal range - determine if the pH is more acidic (7.35-7.4),
or alkaline (7.4-7.45)- this will help us determine compensation
▪ Next, look at PaCO2- determine if it is below 35 (or more alkaline), in
normal range, or above 45 (or more acidic).
▪ Then, look at the HCO3- determine if it is below 22 (or acidic), in normal range,
or above 26 (or alkaline).
▪ Once all readings have been determined, use the ROME method to determine
the ABG imbalance.
, ●Respiratory Opposite- the pH and CO2 levels will be in opposite
directions, Metabolic Equal- the Ph and HCO3 levels will be in the
same or equal direction.
▪ Next look at the PaO2. In our respiratory clients, we must look at this to
determine if there is enough oxygen getting into the lungs or not. If it is lower
than 80, then we know there is not enough perfusion of oxygen within the
arterial blood and that there is breathing difficulty somewhere.
▪ Then we must determine if the patient is fully compensated, partially
compensated, or uncompensated.
● Fully Compensated vs. Partially Compensated vs. Uncompensated
o Compensation occurs when there is an acid base imbalance and the body attempts
to correct an abnormality within the other body system.
▪ First the pH will be affected due to being a buffer. Must look to see if it
is normal, abnormal, acidic, alkaline.
▪ Then we will look at PaCO2 and HCO3. Whichever value is abnormal, that
is your compensation.
o Fully Compensated: The body has placed the pH back to normal. However, there will
be other systems with abnormal ranges. The abnormal value is the body systems that are
compensating. pH normal and HCO3 and PaCO2 are both abnormal. 7.37, 60, 18
o Partially Compensated: The body is compensating for the pH and for both the PaCO2
and HCO3. This places all 3 levels abnormal. This shows that the respiratory and kidneys
are compensating to get the pH back to normal. 7.3, 50, 18
o Uncompensated: The body is not in a state of compensation yet, so there is an
abnormality of the pH and either the PaCO2 or HCO3, but not both. 7.3, 60,
24
● Buffers
o Chemical (bicarbonate and intracellular fluid) and protein buffers (albumin
and globulins)
▪ First line of defense
● Either bind or release hydrogen ions as needed
● Respond quickly to changes in pH
o Respiratory buffers
▪ Second line of defense
● Control the level of hydrogen ions (within minutes) in the blood
through the control of CO2 levels
● When a chemoreceptor senses a change in the level of CO2, a signal
is sent to the brain to alter the rate and depth of respirations.
o Hyperventilation: Decrease in hydrogen ions (helps to blow
off excess hydrogen ions), decreased PaCO2. Central
chemoreceptors inhibited.
o Hypoventilation: Increase in hydrogen ions, increased
PaCO2. Central chemoreceptors stimulated.
o Kidney buffers
▪ Kidneys are the third line of defense.
, ● This buffering system is much slOwer tO respOnd (24-48 hOurs), but it
is the mOst effective buffering system with the lOngest duration.
(kidney mOvement Of bicarbOnate, fOrmation of acids [HPO4 -1 +
H+ → H2PO4 2-], and fOrmation of ammOnium [NH3+ + H+ →
NH4+])
● Kidneys control the movement of bicarbonate in the urine. Bicarbonate
can be reabsorbed into the bloodstream or excreted in the urine in
response to blood levels of hydrogen.
● Kidneys can also produce more bicarbonate when needed.
o High hydrogen ions: Bicarbonate reabsorption and production
o Low hydrogen ions: Bicarbonate excretion
● pH Regulation
o The pH is the expression of the balance between carbon dioxide (CO2), which is
regulated by the lungs, and bicarbonate (HCO 3-), a base regulated by the kidneys. The
greater the concentration of hydrogen, the more acidic the body fluids and the lower
the pH. The lower the concentration of hydrogen, the more alkaline the body fluids and
the higher the pH.
o Example:
o When excess carbon dioxide is produced, the equation shifts to the right, causing
an increase in hydrogen ions (and a decrease in pH).
▪ Whenever the CO2 level changes, the pH changes to the same degree, in
the opposite direction
▪ When the CO2 level of a liquid increases, the pH drops, indicating more
free hydrogen ions (more acidic)
▪ When the CO2 level of a liquid decreases, the pH rises, indicating fewer
free hydrogen ions (more alkaline).
● Causes of imbalances and treatment
o Respiratory Acidosis
▪ What is it:
● pH lower than 7.35
● PaCO2 greater than 45
● HCO3 normal range (unless partially compensated)
● PaO2 less than 80
● The patient may have CO2 retention, increase H+ ions, causing the
pH and CO2 levels to be more acidic. CO2 is an acid in the body
▪ Causes
● Hypoventilation
● COPD
● Asthma
● Pneumonia
