What is the Normal amount of H+ in the ECF?
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?
What does the Henderson-Hasselbalch equation describe?
Relationship b/t pH, PaCO2, and Serum Bicarb
What is the Solubility Coefficient for CO2?
What is a base?
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
What are the Primary Systems that regulate H+ and Prevent Acidosis/Alkalosis?
Chemical Acid-Base Buffers of Body Fluid
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?
How much Filtered Bicarb is reabsorbed in the Proximal Tubule?
The rest reabsorbs in the Distal Tubule
By which mechanism is H+ secreted in Distal Tubule?
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?
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?
How much does the PaCO2 increase w/ a 1 mEq/L increase in Bicarb?
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)
How is Alkalosis treated?
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