Acid Base Balance 1/2 Flashcards
Practice drawing out the schematic for Acid and base balancing as a general overview.
On a titration curve for bicarbonate buffer system, where is the normal operating point in the body?
Fruit juice paradox: Fruit juices make blood more ____
Alkaline
(fruit juices contain CITRATE, which abstracts H+ ions from the body, causing the body to have [HCO3} > [H]
Proximate the cause of respiratory acidosis
Increased PCO2
(it’s the ‘ingredient’ the body uses to make H2CO3 via carbonic anhydrase activity)
Proximate the cause of Respiratory alkalosis
Decreased PCO2
Proximate cause of Metabolic acidosis
Addition of acids other than CO2 or H2CO2
Removal of alkali (fixed PCO2) - eg, diarrhea
Proximate cause of mtabolic alkalosis
Addition of alkali
Removal of acids other than CO2 or H2CO3 (fixed PCO2) - eg vomiting
Clinical causes of respiratory acidosis
- Decreased alveolar ventilation, seen in drug overdose
- Decreased lung diffusing capacity like in pulmonary edema
- V/Q mismatch
Clinical causes of respiratory alkalosis
- Increased alveolar ventilation
- Hypoxia
- Anxiety (due to episodes of hyperventilation)
- Aspirin intoxication
Clinical causes of metabolic acidosis
- Decreased urinary secretion of H+ like in renal failure
- Ketoacidosis like in DM
- Lactic acidosis like in shock
- HCO3 loss likewith severe diarrhea
Clinical causes of metabolic alkalosis
- HCO3 load like in NaHCO3 therapy
- Loss of H+ like with severe vomiting
What acid base parameters are presentin our acidosis/alkaloses?
(Last part of the table)
What do buffer systems do? What about what they don’t do?
Buffer systems of the body fluids react in seconds to minimize the changes H+ concentrations.
Buffer systems do not eliminate H+ from the body or add them to the body, but only keep them tied up until balance can be re-established.
What is the second line of defense and when does it kick in?
The second line defense , the respiratory system, acts within a few minutes to eliminate CO2 and, therefore H2CO3 from the body.
When do the kidneys kick in?
These first two lines of defense keep the H+ concentration from changing too much until the more slowly responding third line of defense, the kidneys, can eliminate excess acid or base from the body.
Although the kidneys are relatively slow to respond compared with the other defenses, over a period of hours to several days, they are by far the most powerful of the acid-base regulatory systems.
If CO2 changes, you correct by:
If CO2 changes, you correct by altering bicarbonate, or “breathing off” of CO2
Diagram out buffering of blood pH
Effectiveness and when the effectiveness changes for the bicarb buffering system
The relative contribution of the bicarbonate system is striking in the interstitial fluid which lacks cellular elements and also has lower protein (major non bicarbonate buffer) concentrations.
However, bicarb buffering is only effective in an open system (the normal functioning system of the body). In closed systems (i.e. ischemia) the buffering capacity of bicarb is reduced due to its inability to “refresh” its pool of its acidic and basic forms
What are these points?
A = normal, B = resp acidosis, D = increase bicarb production from kidneys to return pH to normal levels
The Kidneys Regulate Extracellular H+ Concentration (pH) by:
Secretion of H+
Reabsorption of filtered HCO3-
Production of new HCO3-
What is the main exporter in the nephron pathway for HCO3?
Note: the Na+ 3HCO3- symporter in the proximal tubule is the main exit for HCO3-
HCO3 reabsorption depends on:
HCO3 reabsorption depends on H+ secretion
Where in the nephron is HCO3 reabsorbed?
Compare an H+ secreting intercalated cell vs. an HCO3 secreting intercalated cell
Of these two cells below, one will be more active than the other depending on the pH of the blood. What state of the blood will cause which one to be more active?
(acidic blood = H+ secreting cell active)
Where alongthe nephron is HCO3 reclaimed?
Where along the nephron is HCO3 generated?
Discuss the renal contribution of new bicarbonate to the blood in different states
What are the nonrenal mechanisms of acidifying the blood?
What are the nonrenal mechanisms of alkalinizing the blood?
What are the renal mechanisms of acidifying the blood
What are the renal means of alkalinizing the blood
Respiratory acidosis vs. respiratory alkalosis
In respiratory acidosis/alkalosis, the kidneys alter blood pH by altering:
In respiratory acidosis/alkalosis, the kidneys alter blood pH by altering bicarb levels
Metabolic acidosis vs. metabolic alkalosis
In metabolic acidosis/alkalosis, the lungs correct the pH changes via:
In metabolic acidosis/alkalosis, the lungs correct the pH changes via altering amount of CO2 in the blood
___ and ___ are increased during acidosis and decreased during alkalosis but the mechanism is unknown
Glutaminemetabolism and NH4+ excretion
Tubular hydrogen ion secretion is affected by what in regards to PCO2?
See the second portion below
Acid base status is determined by looking at three values:
pH
HCO3-
PCO2
What PCO2 levels and HCO3 concentrations do we associate with the differing alkaloses and acidoses?
How do we know if we are dealing with a mixed acid-base disorder?
This is an example of what?
Mixed acid base disorder
Relate Aspirin to mixed acid-base disorder and what we may see that will cue us in to thinking about Aspirin overdose
What defines renal tubular acidosis?
Failed HCO3 reabsorption and/or H+ secretion
What defines diarrhea?
Loss of HCO3 from the GI tract
What defines DM?
Lipid conversion to acetoacetic acid as a nurtient source replacement for glucose
What defines chronic renal failure?
Failure of acid secretion and reduced new HCO3 production
How can diuretics lead to metabolic alkalosis?
What is anion gap and how do we define it?
Why does K+ secretion lead to increased tubular secretion of H+?
If low serum K+, body will reabsorb it from the collecting duct by secreting more H+
Folks, take a look at FA which does a great job at explaining all of this.
Free Card!
