Acid-Base Principles and Respirations
Which compensation is faster and which is slower?
Respiratory compensation is *faster!* (minutes) Metabolic compensation is *slower* (days)
Causes of respiratory acidosis? (3)
Respiratory depression due to sedative overdose (opioid, benzodiazepines, or others) Mismatch of ventilation and perfusion Severe emphysema or pneumonia
Some causes of *metabolic acidosis*? (3)
Ketone bodies (weak acids) produced in diabetes Lactate produced by hypoxic tissues during surgery or tissue stress Kidney failure (inability to excrete fixed acid)
*Le Chatlier's* How do the kidneys effect the ever important equation?
Kidneys *remove H+* Equation should proceed to the right
How will the body compensate for *respiratory alkalosis*?
Kidneys excrete bicarbonate, trying to decrease pH.
*Le Chatlier's* How does taking Tums change our cool equation?
*Increase pH* by decreasing [H+] Tums (CaCO3) will increase the right side of the equation and drive it left.
with Respiratory acidosis does bicarbonate levels increase or decrease? Why? Will pH increase or decrease?
*Increase*, adding *more CO2* will drive reaction to right and add more HCO3- as well. pH decreases
In metabolic acidosis on a davenport diagram... will a change follow the isopleth or buffer line? So... what is happening to bicarbonate?
*PCO2 isopleth* Bicarbonate decreases
Which pH regulatory system potentially has a much larger impact on blood pH? Which system is more rapid?
*Respiratory system* can have larger impact and more rapid working Respiratory excretes about 10,000 mmol of carbonic acid per day in the form of CO2 (volatile acid) Kidneys excrete about 100 millimoles of acid per day (fixed acid)
*Davenport Diagram* Changes in _____________ will let you move from one PCO2 isopleth to another.
*respiration* Changes in respiration can more you along the buffer line to new PCO2 isopleths.
Metabolic alkalosis 1. What causes it? 2. What drives it?
1. increase in blood pH via metabolic, drug, or toxin disturbance 2. Typically driven by GI
Le Chatlier's principle says that a disruption in a reaction will cause it to respond and go back to equilibrium.... Cool beans. 1. An increase in CO2 will cause.... what?
1. *Decrease* in pH Reaction will proceed to right so also *increase in HCO3-*
How do the kidneys respond to respiratory acidosis? Which way will this drive the great equation? (right or left)
1. *Excrete acid* but can't change PCO2 2. Drive it even further to the right!!!
1. What are some causes of respiratory alkalosis? 2. Which way will the equation go? 3. What will happen to pH? 4. What will happen to bicarbonate?
1. *Hyperventilation* due to *anxiety* or *high altitude* 2. Equation will go left 3. pH will increase 4. Bicarbonate will drop
1. Which has a greater concentration in typical blood, H+ or Na+? 2. What is the "normal" blood pH?
1. *Na+* by bunches (3.5 million times!!!) 2. blood pH= 7.4 FYI: Values in typical blood: *[H+]* is 4 x 10-8 M (40 nEq/L) *[Na+]* of 0.14 M (140 mEq/L)
*Davenport diagrams* If you hyperventilate, you will move (left and up *or* right and down) If you hold yer breath, you will go to a new isopleth that is (Left and up *or* right and down)
1. *right and down* 2. *Left and up*, induced hypoventilation CO2 stays in blood.
1. What is the normal PCO2? (actual number) 2. Normal blood bicarbonate? 3. Normal pH?
1. 40 mmHg (PCO2) 2. 24 mM (HCO3- 3. 7.4 pH #keepworkinghard
You can get to the same place in two different ways, ex. resp alkalosis with metabolic comp. or metabolic acidosis with resp comp. 1. How do you know which it is? 2. At what pH and bicarb value will this usually happen?
1. ABG, and other (do they have ketoacidosis? or hyperventilation?) 2. pH 7.39 and bicarb of 10 mM
1. What is the most important buffer system? 2. Is it intracellular or extracellular?
1. Bicarbonate buffer system 2. Extracellular
Drugs, metabolic diseases (diabetes, others), and others can effect pH. What are the 2 regulators of blood pH?
1. Respiratory control 2. Renal control
How does the body respond to respiratory problems (acidosis and alkalosis)? During *metabolic compensation* the body can change two out of the three values (HCO3-, PCO2, pH), which can it *not*
1. Responds with *metabolic compensation* 2. *PCO2*, will stay on same PCO2 isopleth trying to change pH
1. Buffers work best at what pH? 2. Why #1 is true? 3. What is the pK of CO2/HCO3- buffer?
1. Work best a *pH near buffers pK* 2. when the pH of a solution is equal to the pK of the buffer, there are equal quantities of acid and its conjugate base 3. 6.1 FYI: phosphate buffer pK is 6.8 which is closer to blood pH but is just not as important
*Respiratory alkalosis* 1. Decreasing what value causes this? 2. driven by?
1. decrease in *PaCO2* 2. driven by *lungs*
1. Respiratory acidosis is an increase in what? 2. What drives respiratory acidosis?
1. increase in PaCO2 2. driven by lungs 3. example of acute resp acidosis: holding breath, blood pH will drop.
1. What does the henderson-hasselbalch equation allow us to calculate? 2. when conjugate base (A-) and acid (HA) are at equal amounts what is your pH? 3. If HA > A-, then pH _____ pK 4. If A- > HA, then pH _______ pK
1. pH of a buffered solution 2. pH will equal pK 3. If HA > A-, then pH *<* pK 4. If A- > HA, then pH *>* pK *log of a number less than 1 is a negative number. So pH will drop. Don't have to calculate but he thinks this will be helpful. *When calculating for blood, (.03 x PaCO2) is substituted for acid
1. Whats the job of a buffer? 2. A buffer is the combination of a __________ _________ and it's __________ ___________.
1. to *keep pH nearly constant* even with addition of strong acid/base (Soaks up extra H+ or OH-) 2. A buffer is the combination of a *weak acid* and it's *conjugate base*.
1. At what levels of pH will problems occur? 2. At what levels of pH will death occur?
1. when pH is *below 7.2* or *above 7.55* 2. Death occurs outside of 6.9 and 7.8 *we have a fairly narrow range of acid concentration that we can tolerate
What is acidosis versus alkalosis?
Acidosis= decreased pH Alkalosis= increase pH
If you ________ _________ you're _______.
If you ain't first you're last
*Metabolic Alkalosis* What can the body do to compensate? (though it usually doesn't)
It can *decrease respiratory drive*and retain CO2 , in response to increased pH detected by peripheral chemoreceptors.
*Metabolic Alkalosis* What are some causes? (2)
Loss of gastric acid (hyperemesis), such in pregnancy, cholera Overuse of antacids due to heart burn/ulcers/other
Metabolic acidosis: 1. What will change primarily? 2. What typically drives it?
Metabolic acidosis: 1. decrease in blood pH via a metabolic, drug, or toxin disturbance 2. Typically driven by muscles, liver, or GI
What is the *primary disturbance* and *compensatory change* for metabolic alkalosis?
Primary Disturbance: *Bicarbonate UP* Compensation: *PaCO2 UP*
What is the *primary disturbance* and *compensatory change* for metabolic acidosis?
Primary disturbance: *Bicarbonate DOWN* Compensation: *PaCO2 DOWN*
What is the *primary disturbance* and *compensatory change* for respiratory alkalosis?
Primary disturbance: *PaCO2 DOWN* Compensation: *Bicarbonate DOWN*
*Metabolic Acidosis* In response to a drop in blood pH, *peripheral chemoreceptors* will stimulate *respiratory drive*, increasing what? (2)
Tidal volume exchange Respiratory rate
How does our body compensate during metabolic acidosis?
increase *Respiratory drive* -> PaCO2 will decrease -> moving along the new buffer line Will blow off CO2
Davenport diagrams are not used clinically... What three things does it account for?
pH Plasma HCO3- PCO2 (mmHg)
Calculate the pH of [4 x 10^-8]
pH = -log[H+] = -log[4 x 10-8] = 7.4
If HCO3- goes up what will that do to pH?
pH will *increase*
*Metabolic Alkalosis* What happens to pH, HCO3-, and PCO2?
pH will *increase* HCO3- will *increase* PCO2 will *not change*
What is the *primary disturbance* and *compensatory change* for respiratory acidosis?
primary disturbance: PaCO2 UP compensation: Bicarbonate UP
___ ___, ______ learned ____ to ______
uh oh happy learned how to putt