Acid-Base Balance (M) Flashcards
What are the 2 principle of rxns (/ types) of anion gap?
1) Na^+ - (Cl^- + HCO3^-)
2) (Na^+ + K^+) - (Cl^- + HCO3^-)
What is the expected anion gap of Na^+ - (Cl^- + HCO3^-)?
7 - 16 mmol/L
What is the expected anion gap of (Na^+ + K^+) - (Cl^- + HCO3^-)?
10 - 20 mmol/L
What are the causes of increased anion gap?
1) Uremia
2) Lactic acidosis
3) Ketoacidosis
4) Hypernatremia
5) Ingestion of methanol
6) Ethylene glycol
7) Salicylate
What is the other fxn of increased anion gap?
It is also used as an assessment of instrument errors
What are the causes of decreased anion gap?
1) Hypoalbuminemia
2) Hypercalcemia
What is a buffer?
It is a system that can resist change in pH
What is the characteristic of buffer?
It is composed of a weak acid or a weak base and its corresponding salt
What are the 4 buffer systems of clinical importance w/c exist in whole blood?
1) The bicarbonate-carbonic acid buffer system
2) The protein buffer system
3) The phosphate buffer system
4) The hemoglobin buffer system
What does the bicarbonate-carbonic acid buffer system use?
1) HCO1^-
2) H2CO3
What is the fxn of HCO1^- and H2CO3 (in bicarbonate-carbonic acid buffer system)?
To minimize pH changes in plasma and erythrocytes
What is the most impt buffer system in plasma?
The bicarbonate-carbonic acid buffer system
What does the protein buffer system use?
Plasma proteins
What is the fxn of plasma proteins (in the protein buffer system)?
To minimize pH changes in the blood
What are used by the phosphate buffer system?
1) HPO4^-2
2) H2PO4^-1
What is the fxn of HPO4^-2 and H2PO4^-1?
To minimize pH changes in plasma and erythrocytes
What does the hemoglobin buffer system use?
Hemoglobin
Where is the hgb (in the hemoglobin buffer system) present?
In RBCs
What is the fxn of hgb (in the hemoglobin buffer system)?
To minimize pH changes in the blood
What is the most impt intracellular buffer?
The hemoglobin buffer system
What is respiration?
It is the process to supply cells w/ O2 for metabolic processes and remove the CO2 produced during metabolism
What is partial pressure?
In a mixture of gases, it is the amt of pressure contributed by each gas to the total pressure exerted by the mixture
When does acidemia occur?
When arterial blood pH is < 7.35
When does alkalemia occur?
When arterial blood pH is 7.45 >
What is hypercapnia?
It is condition of increased blood PCO2
What is hypocapnia?
It is a condition of decreased blood PCO2
What is the meaning of PCO2?
Partial pressure of carbon dioxide
PCO2 is measured in blood as what?
mmHg
What is the meaning of cdCO2?
Concentration of dissolved carbon dioxide
cdCO2 includes what?
1) Undissociated carbonic acid (H2CO3)
2) CO2 dissolved in blood (represented by PCO2)
What is the meaning of ctCO2?
Concentration of total carbon dioxide
ctCO2 includes what?
1) Bicarbonate (HCO3^-)
2) Carbamino-bound CO2
3) Carbonic acid
4) Dissolved CO2
What is the primary component of ctCO2?
HCO3
True or False
The pH of plasma is a fxn of 2 independent variables
True
*What are the 2 independent variables where pH of plasma plays a fxn?
1) Partial pressure of carbon dioxide (PCO2)
2) Concentration of bicarbonate (HCO3)
What organ is responsible for regulating the PCO2?
Lungs
What is the mechanism (/ mechanism done by the lungs) done to regulate PCO2?
Respiratory mechanism
What organ is responsible for regulating the concentration of HCO3?
Kidneys
What is the mechanism (/ mechanism of kidneys) done to regulate the concentration of HCO3?
Renal mechanism
CO2 is transported as / by what?
HCO3, carbamino compound, and dissolved CO2
*A carbamino compound is bound to what?
1) Serum proteins
2) Hgb
What is the other fxn of HCO3, carbamino compound, and dissolved CO2?
They also serve as buffers to maintain blood pH
True or False
CO2, pH, and PCO2 are related accdg to Henderson-Hasselbalch equation
True
*What is the Henderson-Hasselbalch equation?
pH = pK’ + log [HCO3^-]/ [H2CO3]
pH = 6.1 + log cHCO3^-/ cdCO2
In connection to Henderson-Hasselbalch equation, cdCO2 is equal to what?
cdCO2 = PCO2 X ⍺ (solubility coefficient of CO2)
where ⍺ = 0.03 mmol/L per mmHg
What is the reference range of pH for arterial blood gas analysis?
7.35 - 7.45
What is the reference range of ctCO2 for arterial blood gas analysis?
22 - 26 mmol/L
What is the reference range of PCO2 for arterial blood gas analysis?
35 - 45 mmHg
Acid-base disorders are classified as what?
1) Metabolic acidosis
2) Metabolic alkalosis
3) Respiratory acidosis
4) Respiratory alkalosis
Metabolic acid-base disorders primarily involve what?
HCO3 concentration
Respiratory acid-base disorders primarily involve what?
Dissolved CO2 concentration
What is the principle of metabolic acidosis (non respiratory)?
Primary HCO3 deficit
What is the mechanism / principle present in metabolic acidosis?
The HCO3 concentration decreases, causing a decrease in the 20:1 ratio between cHCO3 and cdCO2, w/c results in a decrease in the blood pH
What may be the causes of metabolic acidosis?
1) Organic acid production
2) When ingestion exceeds the excretion rate
What are the disorders included in metabolic acidosis (non respiratory)?
1) Diabetic ketoacidosis
2) Lactic acidosis
2) Poisonings (such as salicylate, ethylene glycol, and methyl alcohol)
4) Reduced acid excretion
5) Loss of HCO3
What is the cause of diabetic ketoacidosis?
Production of acetoacetic acid and β-hydroxybutyric acid
What is the cause of lactic acidosis?
Production of lactic acid
What is the cause of reduced acid excretion?
Renal failure or tubular acidosis
What is the cause of loss of HCO3?
Diarrhea or excessive renal excretion
What are the laboratory findings if pt has metabolic acidosis (non respiratory)?
1) ctCO2: decreased
2) PCO2: normal
3) pH: decreased
In metabolic acidosis (non respiratory), what is the respiratory compensatory mechanism?
A decreased pH triggers hyperventilation that lowers PCO2 and results in an increase in pH. This increases the ratio between cHCO3 and cdCO2 to 20:1, w/c increases the blood pH
In metabolic acidosis (non respiratory), what are the laboratory findings after / in compensation?
1) ctCO2: decreased
2) PCO2: decreased
3) pH: normal
What is the principle of metabolic alkalosis (non respiratory)?
Primary HCO3 excess
What is the mechanism / principle in metabolic alkalosis (non respiratory)?
The HCO3 concentration increases, causing an increase in the 20:1 ratio between cHCO3 and cdCO2, w/c results in an increase in the blood pH
What may be the causes of metabolic alkalosis?
1) Ingestion of excess base
2) Decreased elimination of base
3) Loss of acidic fluids
What are the disorders included in metabolic alkalosis (non respiratory)?
1) Ingestion of excess alkali (antacids)
2) Intravenous administration of HCO3
3) Renal HCO3 retention
4) Prolonged diuretic use
5) Loss of HCl from the stomach after:
a. Vomiting
b. Intestinal obstruction
c. Gastric suction
6) Glucocorticoid excess (present in Cushing syndrome)
7) Mineralocorticoid excess (as in hyperaldosteronism)
What are the lab findings present for a pt w/ metabolic alkalosis (non respiratory)?
1) ctCO2: increased
2) PCO2: normal
3) pH: increased
What is the respiratory compensatory mechanism done in metabolic alkalosis (non respiratory)?
The pH increase slows breathing (hypoventilation), thus increasing the amt of CO2, retained by the lungs. This increased CO2 retention causes an increase in H2CO3, w/c results in more dissolved CO2 in the blood. The carbonic acid lowers the pH. This decreases the ratio between cHCO3 and cdCO2 to 20:1, w/c decreases the blood pH
What are the lab findings after / in compensation for metabolic alkalosis (non respiratory)?
1) ctCO2: increased
2) PCO2: increased
3) pH: normal
What is the principle of respiratory acidosis?
Primary cdCO2 excess expressed as increase in PCO2 (hypercapnia)
What is the mechanism / principle of respiratory acidosis?
Inability of a person to exhale CO2 through the lungs (hypoventilation) causes an increase of PCO2. The increased PCO2 causes an increase in the concentration of dissolved CO2, w/c forms carbonic acid in the blood. This decreases the 20:1 ratio between cHCO3 and cdCO2, w/c decreases the blood pH
What may be the causes of respiratory acidosis?
1) Chronic obstructive pulmonary disease
a. Chronic bronchitis
b. Emphysema
c. Ingestion of narcotics and barbiturates
2) Severe infections of the CNS
a. Meningitis
What are the lab findings present if a pt has respiratory acidosis?
1) ctCO2: normal
2) PCO2: increased
3) pH: decreased
What is the renal compensatory mechanism done in respiratory acidosis?
The kidneys increase sodium hydrogen exchange, NH3 formation, and HCO3 retention. The increased HCO3 concentration aids the return of the 20:1 ratio, w/c raises the blood pH
What are the lab findings after / in compensation for respiratory acidosis?
1) ctCO2: increased
2) PCO2: increased
3) pH: normal
What is the principle in respiratory alkalosis?
Primary cdCO2 deficit expressed as decrease in PCO2 (hypocapnia)
What is the mechanism / principle in respiratory alkalosis?
Decreased PCO2 results from an accelerated rate or depth of respiration, or a combination of both. Excessive exhalation of CO2 (hyperventilation) reduces the PCO2, causing a decrease in the concentration of dissolved CO2, w/c forms less H2CO3 in the blood (i.e., less hydrogen ions). This increases the 20:1 ratio between cHCO3 and cdCO2, w/c increases the blood pH
What may be the causes of respiratory alkalosis?
1) Hypoxia
2) Anxiety
3) Nervousness
4) Excessive crying
5) Pulmonary embolism
6) Pneumonia
7) Congestive heart failure (CHF)
8) Salicylate overdose
What are the lab findings if a pt has respiratory alkalosis?
1) ctCO2: normal
2) PCO2: decreased
3) pH: increased
What is the action / aim of renal compensatory mechanism for respiratory alkalosis?
It corrects respiratory alkalosis by excreting HCO3
What are the lab findings of a pt w/ respiratory alkalosis in / after compensation?
1) ctCO2: decreased
2) PCO2: decreased
3) pH: normal
