Section 11 (Acid-Base Regulation) Flashcards
What are the normal resting levels of pH, [HCO3], and PACO2?
pH = 7.35-7.45 [HCO3] = 22-26 mM (24 mM) PCO2 = 35-45 mm Hg (40 mm Hg)
What is the addition of [H+] buffered by within a few minutes?
Hb**, albumin, and HCO3
How does the body compensate for increased [H+] in minutes to hours?
Increased Ve to remove CO2 (compensation for metabolic acidosis?
How does the body compensate for increased [H+] in hours and days?
CO3 (bone carbonate) is released from bone; patients with chronic acid compensation have weak bones
What does “compensated” acidosis mean?
“compensated” means that the added [H+] to the blood is buffered to an extent or amount that the blood pH is within the normal limits or ~ 7.4 (7.36)
What does the Base Excess (BE) of the kidney mean?
A BE > +2 means that the kidneys are retaining base[HCO3-].
A BE < -2 means that the kidneys are excreting base [HCO3-].
Normal laboratory values for BE are between -2 and +2.
How does a person with respiratory acidosis compensate?
Person will have a BE of >2+, indicating kidneys are reabsorbing base in order to buffer the adde [H+]
What should a PT keep in mind when working with a person who has chronic (after several months) compensated respiratory acidosis?
Their bones will be very weak and only a gentle passive force should be applied (if needed) to reduce the probability of a pathological fracture of the stressed bone.
What are the non bicarbonate buffer systems in the blood and kidneys?
Blood = Hb and other plasma proteins (albumin) Kidneys = phosphates (HPO4) and ammonia (NH3)
What is the source of NH3 in the body?
Tubular cells of the kidney
What increases the concentration gradient of NH3 from the tubular cells of the kidney into the tubular fluid (urine)?
Decreasing the urine pH from 9.0 to 4.0 (as [H+] is in urine, combines with NH3 to produce NH4); NH3 is a base and it flows towards its concentration gradient. Once combined with H+, it becomes an acid and further decreases the pH of the urine, resulting in more of a concentration gradient for other NH3 molecules to flow down
Where does HPO4- - buffer or bind H+?
Within the urine or tubular fluid.
Increased PCO2 in the blood [increases/decreases] the pH of the blood, while decreased PCO2 in the blood [increases/decreases] the prof the blood.
decreases; increases
What compensations does the body make after several months of chronic fully compensated respiratory acidosis?
- pt will have BE>2+
- [H+] will be buffered by HCO2. Hb, and bone CaCO3
- There will be increased H+ excretion as NH4 and H2PO4 by the kidneys
The ______ system compensates for metabolic disturbances and the _____ system compensates for respiratory disturbances.
Respiratory; Metabolic
What substances are reabsorbed from tubular fluid into interstitial fluid?
- HCO3
- CO2
- H+
- Na+
What substances are secreted into the tubular fluid from tubular cells?
- NH3
- H+
- CO2
- HCO3
What causes respiratory acidosis and alkalosis?
Acidosis = decrease in ventilation (can't get rid of CO2) Alkalosis = increase in ventilation
In a patient with respiratory acidosis, their PCO2 levels would be [high/low/normal] and their HCO3 would be [high/low/normal].
high; normal
In a patient with metabolic acidosis, their PCO2 levels would be [high/low/normal] and their HCO3 would be [high/low/normal].
normal; low
In a patient with respiratory alkalosis, their PCO2 levels would be [high/low/normal] and their HCO3 would be [high/low/normal].
low; normal
In a patient with metabolic alkalosis, their PCO2 levels would be [high/low/normal] and their HCO3 would be [high/low/normal].
normal; high
What would the compensation be for acute respiratory acidosis?
Kidneys would compensate and BE would be >2+ (urine would be more acidic)
What would the compensation be for acute metabolic acidosis?
The lungs would compensate by hyperventilation
