Acid-Base Flashcards
pH of normal blood reference range
7.35-7.45
What maintains blood pH
coordinated function of the lungs, kidneys and blood buffers
What are the four blood buffering systems
bicarbonate, hemoglobin, phosphate and plasma proteins
Why is the bicarbonate buffering system the most important
carbonic acid dissociates into carbon dioxide and is eliminated in the lungs
the lungs can modify the respiration rate and thus the pCO2
kidneys can control bicarbonate reabsorption
What is total CO2
the sum of the concentration of bicarbonate and dissolved CO2
What is dissolved CO2
the solubility coefficient multiplied by the partial pressure of CO2
pCO2
the pressure exerted by CO2 in a gas mixture
How is acid-base balanced by the lungs
CO2 is carried in RBCs and converted to H2CO3 which then dissolves into bicarbonate and hydrogen
In the lungs hemoglobin binds oxygen releasing the H which binds to form H2CO3, which then dissociates into CO2 and H2O
What does hyperventilation do
decreases the amount of CO2 in the blood raising pH
What does hypoventilation do
increases the amount of CO2 in the blood decreasing the pH
How is acid-base balanced by the kidneys
renal tubules regulate bicarbonate concentration by controlling the rate of reabsorption
they can also increase the amount of hydrogen excreted if needed
What is metabolic acidosis
a bicarbonate deficit causing a decrease in blood pH
What causes metabolic acidosis
Increased endogenous acids:
lactic acid - increased anion gap
keto acids - increased anion gap
Increase in exogenous acids:
ethanol - increased anion and osmolal gap
methanol - increased anion and osmolal gap
ethylene glycol - increased anion and osmolal gap
salicylates - increased anion gap (can also cause mixed results due to decreasing pCO2)
Inability to excrete acid
uremia/renal failure - increased anion gap
renal tubular necrosis - normal anion gap
Loss of bicarbonate
diarrhea, pancreatitis. intestinal fistula
How does the body compensate for metabolic acidosis
hyperventilation and renal adjustment (normal kidney function)
What is respiratory acidosis
excess CO2 due to hypoventilation
What causes respiratory acidosis
factors that depress the respiratory center (drugs, trauma, tumour)
mechanical obstruction of the airways (COPD, pulmonary fibrosis, asthma, infeciton)
Other causes (abdominal distention, obesity, sleep disorders)
How does the body compensate for respiratory acidosis
blood buffer via hemoglobin and protein
renal compensation (slow to react) via increasing the NA-H exchange, ammonium formation and reclamation of bicarbonate
What is metabolic alkalosis
an excess of bicarbonate
What causes metabolic alkalosis
hypochloremic alkalosis (loss of chloride)
excess of mineralocorticoids or corticoids (hyperaldosteronism and cushings syndrone)
excessive administration of bicarbonate (IV)
How does the body compensate metabolic alkalosis
hypoventilation to raise the CO2
if it persists the body will attempt to decrease bicarbonate reclamation
What is respiratory alkalosis
results from hyperventilation
What causes respiratory alkalosis
factors that have a direct stimulatory effect on the respiratory system (hysteria, fever, drugs, hypoxia)
factors that effect the pulmonary mechanism and lead to tissue hypoxia (pneumonia, emboli, congestive heart failure)
How does the body compensate for respiratory alkalosis
renal trying to decrease reclamation of bicarbonate and increase reclamation of hydrogen
pCO2 reference range
35-45 mmHg
pO2 reference range
70-90 mmHg
HCO3 reference range
20-27 mmol/L
What is the ratio of dissolved CO2 to bicarbonate in the blood
1:20
