Acid-Base Regulation - Quiz 4 Flashcards
What is the Normal amount of H+ in the ECF?
40 nEq/L
The Lower & Higher Limit of pH at which a person can live for a few hours is ___ & ___ respectively.
The Lower & Higher Limit of pH at which a person can live for a few hours is 6.8 & 8.0 respectively.
What is an acid?
Proton Donor
What does the Henderson-Hasselbalch equation describe?
Relationship b/t pH, PaCO2, and Serum Bicarb
What is the Solubility Coefficient for CO2?
0.03 mmol/mmHg
What is a base?
Proton Acceptor
What is the role of Weak Acids or Bases in regards to pH?
Act as Buffers to minimize pH changes
When are pH buffers most efficient?
When pH = pKA
What are the pH Body Buffers?
Bicarb - strongest ECF buffer
Hgb
Proteins
Phosphate
Ammonia
What are the Primary Systems that regulate H+ and Prevent Acidosis/Alkalosis?
Chemical Acid-Base Buffers of Body Fluid
Respiratory Center
Kidneys - slowest, but strongest regulator
True or False: The Bicarb buffer is effective Against both Metabolic & Respiratory acid-base imbalances.
FALSE - Bicarb is effective against Metabolic, but not Respiratory acid-base imbalances
What is the pKa of Bicarb?
pKa = 6.1
How do the Kidneys increase Bicarb Reabsorption during Acidosis?
- CO2 + Water = H2CO3 (Carbonic Acid)
- H2CO3 —> H+ + HCO3-
- H+ secreted into Proximal Tubule & Bicarb is Reabsorbed
- H+ in Proximal Tubule combines w/ Filtered Bicarb = H2CO3-
- Carbonic Anhydrase replaces CO2 by Splitting Bicarb into CO2 & Water
By which mechanism is H+ secreted into the Tubular Fluid?
Sodium-Hydrogen Counter-Transport
How much Filtered Bicarb is reabsorbed in the Proximal Tubule?
80-90 %
The rest reabsorbs in the Distal Tubule
By which mechanism is H+ secreted in Distal Tubule?
H+ Pump
How is H+ secreted into the Tubular Fluid in the Collecting Duct?
K+ is exchanged for H+
How does Phosphate play a role in Acid Excretion?
HPO42- combines w/ the H+ in the Tubule Fluid to form H2PO4- which CANNOT be reabsorbed and gets trapped in urine
Why is Phosphate effective as a buffer in acidic urine?
Phosphate has pKA of 6.8
How does Ammonium (NH4) work as a Buffer in the Collecting Tubules vs the Proximal, Distal, & TAL?
Collecting Duct - Ammonia (NH3) combines w/ H+ to make NH4, then excreted. Bicarb is made in the process
Proximal, Distal, & TAL - NH4 is made from Glutamine, then excreted. Bicarb is made in the process
What is the main mechanism of Acid Elimination w/ Chronic Acidosis?
NH4 Excretion
What are the common situations in which Alkalosis occurs?
Sodium Depletion/Contraction Alkalosis - More sodium goes into Proximal Tubule & Co-Transports Chloride. Bicarb is reabsorbed in exchange w/ Chloride. This happens w/ chronic diuretics.
Increased Aldosterone - Increases Na reabsorption & H+ secretion in the Distal Tubule
What is Base Excess?
Amount of Acid/Base needed to return pH back to 7.4
(+) = Metabolic Alkalosis
(-) = Metabolic Acidosis
What causes Increased H+ Secretion & Bicarb Reabsorption?
↓ECF
↑Angiotensin II
↑Aldosterone
Hypokalemia
Hypocalcemia
How much does the PaCO2 increase w/ a 1 mEq/L increase in Bicarb?
~ 0.5
How does Potassium Levels change w/ a 0.1 increase in pH?
~ 0.5 mEq/L
How is Metabolic Acidosis treated?
Treat Underlying Cause
Sodium Bicarb (Dont give to pts w/ Resp Failure)
Dialysis
How is Alkalosis treated?
IV HCl
Spironolactone
Treat Underlying Problem
How is the Cerebral Blood Flow affected by reducing ventilation by half & doubling PaCO2?
Doubles Cerebral Blood Flow
How is the Anion Gap calculated?
Na+ - [Cl- + HCO3-]
Normal: 7 - 14 mEq/L
Why does acidosis occur w/ a High Anion Gap?
H+ consumes and ties up all the Bicarb
Occurs w/ DKA, Uremia, and Lactic Acidosis
What causes Metabolic Acidosis w/ a Normal Anion Gap?
Renal Tubular Acidosis
Diarrhea
Carbonic Anhydrase Inhibition
Uteral Diversion
Early Renal Failure
Hydronephrosis
HCl
Saline
What toxins cause a High Anion Gap Acidosis?
Methanol
Ethylene Glycol
Salicylates
Paraldehyde
In Acute Respiratory Acidosis compensation, how much does the Bicarb increase for every 10 mmHg increase in CO2?
Bicarb increases by 1 mEq per 10 mmHg of CO2
In Chronic Respiratory Acidosis compensation, how much does the Bicarb increase for every 10 mmHg increase in CO2?
Bicarb increases 4 mEq per 10 mmHg in CO2
For Metabolic Acidosis compensation, what happens to the CO2 when the Bicarb Decreases?
CO2 decreases 1.2x the decrease in Bicarb
In Acute Respiratory Alkalosis compensation, how much does the Bicarb decrease for every 10 mmHg decrease in CO2?
Bicarb decreases 2 mEq/L per 10 mmHg in CO2
In Chronic Respiratory Alkalosis compensation, how much does the Bicarb decrease for every 10 mmHg decrease in CO2?
Bicarb decreases 2 mEq/L per 10 mmHg in CO2
For Metabolic Alkalosis compensation, what happens to the CO2 when the Bicarb Increases?
CO2 increases 0.7x the increase in Bicarb
