Week 11: Acid Base Inbalance Flashcards
Exam 4
What is the pH scale described as?
Logarithmic, not linear
Solutions with an excess of hydrogen ions are ____in nature.
acidic
Solutions with an excess of hydroxide ions (OH-) are…
basic or alkaline in nature
What is defined as neutral in biologic fluids?
a pH of 7.40
How do body acids form? What do these body acids release?
Body acids form as the end products of protein, carbohydrate, and fat metabolism; these acids can release hydrogen ion.
Base
A base is a substance that accepts hydrogen ions;
Acid
an acid is a substance that donates hydrogen ions.
Body acids exist as what two forms:
- volatile acids
- nonvolatile acids
volatile acids
(substances that can be eliminated as carbon dioxide [CO2] gas)
nonvolatile acids
(substances that can be eliminated only by the kidney).
What is the sole volatile acid formed in the body?
The sole volatile acid formed in the body is carbonic acid (H2CO3), a weak acid
Weak acid
it does not easily release its hydrogen ion.
Examples of nonvolatile acids:
lactic acid, phosphoric acid, sulfuric acid, acetoacetic acid, and beta-hydroxybutyric acid.
Many nonvolatile acids are considered what?
Strong acids
Strong acids
They readily release their hydrogen ions.
How are nonvolatile acids eliminated/
Nonvolatile acids are secreted into the urine by the renal tubules in amounts of approximately 60 to 100 mEq of hydrogen per day, or about 1 mEq per kilogram of body weight.
The body has three mechanisms, or lines of defense, to maintain the acid–base balance:
(1) physiologic (chemical) buffer systems (bicarbonate, phosphate, hemoglobin, and protein), the first line of defense;
(2) respiratory acid–base control, the second line of defense; and
(3) renal acid–base control, the third line of defense.
Buffer systems
resist changes in pH and maintain pH within the normal range
ECF Plasma buffer system two components:
- carbonic acid bicarbonate
- protein hemoglobin
Most important intracellular buffers:
- phosphate and
- protein
WHat are the most important renal buffers:
- Ammonia
- Phosphate
What is the base component of the carbonic-bicarb buffer system
bicarbonate ion
What is the acid component of the carbonic-bicarb buffer system?
hydrogen ion
What do the lungs do with CO2 and how?
The lungs eliminate CO2 and can increase the amount of CO2 eliminated by increasing the rate and depth of ventilation.
What order do the buffering systems respond most to least rapidly?
- physiological buffering system
- lungs
- Kidney
How do kidneys augment the carbonic acid bicarbonate buffer system?
the kidneys augment the carbonic acid–bicarbonate buffer system by reabsorbing or regenerating bicarbonate in the renal tubules or excreting hydrogen into the urine.
How do proteins act in the protein buffering system?
All proteins can attach or release a hydrogen ion.
Where are most proteins located, what does this mean for protein buffering?
Most proteins are inside cells; hence protein-based buffering is primarily an intracellular buffer system.
Example of protein buffer?
Hemoglobin
As pH increases, what happens to hemoglobin?
pH increases, hemoglobin loses hydrogen ions, and the reverse happens when the pH decreases.
How does hemoglobin affect pH when it binds to CO2?
Hemoglobin binds to CO2 to form carbaminohemoglobin (HHbCO2)
The bound CO2 is transported to the lungs, where it is released from the body through ventilation.
Why is CO2 a potential acid?
Unbound CO2 can dissociate in water to form H2CO3, a weak acid.
Unbound CO2 can dissociate in water to form H2CO3, a weak acid.
What does hemoglobin do when binded to CO2?
By binding carbon dioxide, the hemoglobin is preventing CO2 from dissociating into carbonic acid;
it thereby prevents the release of excess H+ ions into the environment.
What is the bicarbonate-carbonic acid buffer functional within?
WIthin the kidney
What are the two additional buffer systems active within the renal tubules
- Phosphate buffer
- Ammonia buffer
When would H+ react with either phosphate or ammonia buffer?
Once H+ has reacted with all available HCO3- , any additional H+ ions react with either the phosphate or the ammonia buffer systems.
The two components of the phosphate buffer system? What do they function in association with?
- monobasic phosphate (H2PO4-) and
- dibasic phosphate (HPO4-)
Usually function in association with sodium to form a sodium salt
What are the components of the ammonia buffer? What do they do?
- ammonia (NH3) and
- ammonium (NH4 +).
These components reversibly bind or release hydrogen ion to maintain a neutral pH.
What do kidneys do with excess acids?
They actually can rid the body of excess acids by excreting hydrogen ions into the urine.
What happens to monobasic phosphate and ammonium as they have attached to H+ ions?
Monobasic phosphate (H2PO4-) and ammonium (NH4 +) are secreted into the urine as they have attached hydrogen ions.
In the Renal Acid-base control, what can renal tubules do with bicarbonate?
Renal tubules also can reabsorb bicarbonate into the plasma using a mechanism that involves the bicarbonate-carbonic acid buffer.
acidosis.
A systemic increase in the hydrogen ion concentration or a loss of base
alkalosis
A systemic decrease in the hydrogen ion concentration or an excess of base
Changes in pH of blood may be caused by:
- Respiratory processes
- Metabolic processes
If the altered pH occurs secondary to biochemical processes within the body,
it is said to be metabolic.
If the alteration in pH is secondary to an issue with breathing,
it is said to be respiratory.
Four parameters for arterial blood gases:
- the blood pH
- PaO2 (oxygen)
- PaCO2 (Carbon dioxide)
- Bicarbonate (HCO3-)
Compensation
Renal and respiratory adjustments in response to primary changes in the pH are known as compensation
How does the respiratory system compensate for changes in the pH?
The respiratory system compensates for changes in the pH by altering the rate and depth of ventilation to increase or decrease the concentration of retained carbon dioxide.
What occurs during respiratory acidosis?
A low blood pH signals acidosis. If the PaCO 2 is high, the source of the problem is respiratory
What happens to CO2 levels when breathing shallowly?
Breathing more shallowly retains CO2;
What happens to CO2 levels when breathing more rapidly and deeply?
breathing more rapidly and deeply blows off CO2.
What occurs during metabolic acidosis?
If the pH is low and the PaCO 2 is normal or low, it is caused by metabolic processes within the body.
Example of when respiratory acidosis may occur?
Such a scenario might occur with an opioid overdose, in which respirations are depressed and CO2 is retained. This individual is described as having a primary respiratory acidosis.
Example of primary metabolic acidosis?
An example of a primary metabolic acidosis is an individual experiencing DKA from a lack of insulin secretion or administration. The diabetic individual, lacking insulin, cannot metabolize glucose. The body metabolizes fat stores, and as a result, acid byproducts are released into the blood, causing metabolic acidosis.
How do the lungs compensate for excess acidity?
By breathing more rapidly and deeply, blowing off CO2.
In cases of respiratory acidosis, how does renal compensation occur?
the kidneys attempt to compensate for abnormal pH levels by resorbing bicarbonate ions into the plasma and excreting H+ ions into the urine
In cases of primary metabolic acidosis, how does respiratory compensation occur?
With a primary metabolic acidosis, the lungs attempt to compensate by breathing deeply and rapidly (Kussmaul respirations) in an attempt to rid the body of CO2, a potential acid.
In cases of metabolic acid–base imbalance, what occurs more rapidly, renal or respiratory compensation?
In cases of metabolic acid–base imbalance, respiratory compensation occurs rapidly, within minutes of an abnormal pH. Renal compensation occurs more slowly;
Which works has a greater capacity to restore the normal pH kidney or lungs?
The kidneys have a far greater capacity to restore the normal pH.
How do kidneys attempt to compensate for a primary respiratory alkalosis?
by decreasing the rate of H+ ions excreted into the urine and
reducing the resorption of bicarbonate ions into the plasma.
How do lungs attempt to compensate for a primary metabolic alkalosis?
lungs attempt to compensate for a primary metabolic alkalosis by retaining CO2 with slower and shallower ventilation.
The measured values (laboratory values) of pH, PaCO 2, and HCO3- can identify three parameters:
- the nature of the alteration in pH: acidosis (pH <7.40) or alkalosis (pH >7.40);
- the source of the abnormality—respiratory or metabolic; or
- whether any compensation has developed.
Compensated respiratory acidosis:
If the pH is normal and the bicarbonate level is elevated the respiratory acidosis is described as compensated respiratory acidosis.
Partially compensated respiratory acidosis.
If the pH is near normal and the bicarbonate level is elevated, the respiratory acidosis is described as partially compensated respiratory acidosis.
uncompensated respiratory acidosis
If the pH is low and the bicarbonate level is normal, the respiratory acidosis is described as uncompensated respiratory acidosis because the kidneys have not had sufficient time to compensate for the problem.
In Compensated respiratory acidosis, Partially compensated respiratory acidosis and uncompensated respiratory acidosis how are the PaCo2 levels and why?
In all three cases, the PaCO 2 level will be elevated because the source of the acidosis is respiratory.
Correction
Correction occurs when the values for both components of the buffer pair (bicarbonate and PaCO 2 [carbonic acid]) return to normal levels.
In metabolic acidosis, how are the levels of nonvolatile acids?
In metabolic acidosis , the concentrations of nonvolatile (noncarbonic) acids increase.
hyperchloremic acidosis is caused by:
An increase in the plasma concentration of chloride, out of proportion to sodium, causes hyperchloremic acidosis (non–anion gap acidosis).
The specific type of acidosis can be determined by
examining the serum anion gap
Metabolic acidosis early and late symptoms
Early symptoms include headache and lethargy, which progress to confusion and coma in severe acidosis.
The respiratory system’s efforts to compensate for the increase in metabolic acids result in
Kussmaul respirations
Other symptoms of metabolic acidosis
Other symptoms include anorexia, nausea, vomiting, diarrhea, and abdominal discomfort.
Death can result in the most severe and prolonged cases, preceded by dysrhythmias and hypotension.
What causes metabolic alkalosis
When excessive loss of metabolic acids occurs, the bicarbonate concentration increases, causing metabolic alkalosis
hypochloremic metabolic alkalosis
When acid loss is caused by vomiting, renal compensation is not very effective because loss of chloride (an anion) in hydrochloric acid (HCl) stimulates renal retention of bicarbonate (an anion). The result is known as hypochloremic metabolic alkalosis .
Common signs and symptoms of metabolic alkalosis:
weakness, muscle cramps, hyperactive reflexes, tetany, confusion, convulsions, and atrial tachycardia. Respirations may be shallow, with slow ventilation, as the lungs attempt to compensate by increasing carbon dioxide retention.
Respiratory acidosis occurs with what and results in what
Respiratory acidosis occurs with alveolar hypoventilation, resulting in hypercapnia (an excess of carbon dioxide in the blood).
How is the arterial carbon dioxide pressure (PaCO2) and pH in respiratory acidosis?
The arterial carbon dioxide pressure (PaCO 2) is greater than 45 mm Hg
pH is less than 7.35
Common causes of respiratory acidosis:
Common causes include depression of the respiratory center (e.g., from drugs or head injury),
paralysis of the respiratory muscles, disorders of the chest wall (e.g., kyphoscoliosis or broken ribs), and
disorders of the lung parenchyma (e.g., pneumonia, pulmonary edema, emphysema, asthma, bronchitis).
Clinical presentations of respiratory acidosis:
headache, blurred vision, breathlessness, restlessness, and apprehension, followed by lethargy, disorientation, muscle twitching, tremors, convulsions, and coma.
In respiratory acidosis, what is the skin like? WHy
The skin may be warm and flushed from vasodilation secondary to an elevated carbon dioxide concentration.
Treatment for respiratory acidosis?
- restoring adequate alveolar ventilation to remove the excess CO2 (↓H2CO3).
Respiratory alkalosis occurs why?
Respiratory alkalosis follows alveolar hyperventilation (deep, rapid respirations).
What occurs (having to do with CO2) during respiratory alkalosis?
Hypocapnia (decreased plasma carbon dioxide) decreases the carbonic acid concentration.
What are the PaCO2 levels in Respiratory Alkalosis? How about pH?
Laboratory analysis reveals a PaCO 2 less than 35 mm Hg and an elevated pH
How would secondary alkalosis result from metabolic acidosis?
Secondary alkalosis may result from hyperventilation triggered by metabolic acidosis (a mixed acid–base disorder).
What does Respiratory alkalosis stimulates the central and peripheral nervous systems, what kind of symptoms does this lead to?
Respiratory alkalosis stimulates the central and peripheral nervous systems, resulting in dizziness, confusion, tingling of the extremities (paresthesias), convulsions, and coma.
Symptoms of hypocalcemia are common
What does CO2 do to blood vessels?
Causes vasodilation.
