Acid-Base Physiology Flashcards
Normal values for pH, PCO2, HCO3
.pH: 7.35-7.45
. PCO2:35-45 mmHg
. HCO3: 22-26 mEq/L
Acute respiratory disorder PCO2 and HCO3 conc.
. Inc. PCO2 of 10 mmHg and inc. of HCO3 by 1 mEg/L
. Dec. PCO2 of 10 mmHg and dec. HCO3 by 2
Compensated respiratory disorder PCO2 and HCO3
. Inc. PCO2 of 10 mmHg causes inc. in HCO3 by 4 mRq/L
. Dec. PCO2 by 10 mmHg causes dec. HCO3 by 5 mEq/L
Normal, increased,and decreased base excess
. Normal: 0 =/- 2 mEq/L
. Inc: >+ 2mEq/L
. Dec:
Normal anion gap range
8-16 mEq/L
HCO3 and PCO2 for metabolic acidosis vs. respiratory acidosis
. Metabolic: Dec. HCO3
. Respiratory: inc. PCO2
Metabolic vs respiratory alkalosis
. Metabolic: inc. HCO3
. Resp: dec. PCO2
T/F pH is a function of ratio of plasma bicarbonate to dissolved CO2
T
pH is maintained by _____
. Kidney’s ability to regulate plasma bicarbonate conc.
. Lung’s ability to regulate plasma CO2 conc.
Bicarbonate buffer system
. Most important buffer in the blood
. Accounts for 53% buffering capacity despite having pKa of 6.1 bc of high HCO3 conc., kidney and lung regulation
Hb as buffer
. Accounts for 35% total buffering capacity
. Buffering action is greater in venous blood (pK is 7.85 when de-oxygenated vs 6.6 when oxygenated)
T/F buffers reversible bind and release H as the concentrations change
T
Bone buffers
. Bone has Ca, Na, and K salts of carbonate (CO3)
. In response to inc. H conc., the excess ions are exchanged w/ Ca, Na, and K ions assoc. w/ carbonate on the bone surface
. During chronic metabolic acidosis, osteoclasts in bone are also activated which release CaCO3 and CaPO4 into ECF
. Buffering of H by bone can contribute up to 40% of total buffering capacity during chronic acidosis
Intracellular buffers
. Besides RBCs, proteins, organic and inorganic phosphates are buffers due to their high intracellular conc.
. Intracellular HCO3 is bad buffer bc it has a low intracellular conc.
Buffering for metabolic acidosis
. Poop shoots cause loss of HCO3
. Half of excess H will be buffered by remaining bicarbonate
. Remaining H will enter cells or exchange cations on bone
. Buffering by bicarbonate takes minutes
. Entry and neutralization of H in cells/bone takes 2-4 hrs
. Respiratory system compensate by inc. ventilation
Buffering for respiratory acidosis
. COPD leads to acidosis
. Excess H will be buffered by intracellular buffered since bicarbonate is so low
. Process takes 2-4 hrs
. Renal system will compensate by creating new bicarbonate
Ion exchange due to different H concentrations
. Inc. in extracellular H: H ions will enter cells down conc. Gradient and a cation must leave to keep neutrality (normally K)
. Transcellular ion exchange during acidosis leads to K efflux that can lead to fatal elevation in plasma K
. Reverse exchange causes alkalosis
. Renal cells respond to changes in intracellular H conc. By changing expression of carbonic anhydrase and activity of glutaminase
. In acidosis the rate of bicarbonate recovery and production of new bicarbonate inc.
Law of mass action
. Only applies to respiratory disturbances
. CO2 conc. Will change the HCO3 conc.
. Metabolic issue won’t change won’t change PCO2 bc the extra CO2 would be quickly eliminated
How much acid is produced in an adult per day
. 50-70 mEq/L of acid/day
Acids that contribute to daily acid load
carbonic acid and non-carbonic acids
Carbonic acid
. Metabolism of carbs and fats produces CO2 which combines w/ H2O in RBCs to form carbonic acid
. Reaction facilitated by carbonic anhydrase
.
Non-carbonic acids
. Metabolism of proteins and intake of foods w/ phosphate and sulphates lead to daily acid production
. Metabolism of Cys and Met generate sulfuric acid while metabolism of Lys produces HCl
. Metabolism of Glu generates base
. Net effect is acid production
T/F bicarbonate can be reabsorbed
F, it is not reabsorbed
. There are only mechanisms for bicarbonate recovery and creation of new bicarbonate exist
H in proximal tubule
. CO2 and H2O converted into bicarbonate and H via CA
. H is secreted into lumen and bicarbonate is revered by circulation
. H secreted is neutralized by filtered bicarbonate in early nephron portions
. Bicarbonate is revered by its production and loss (1:1) in prox. Tubule