Acid Base Balance Flashcards
What is the formula for [HCO3-] ?
0.03 PCO2 x 10 ^(pH-6.1)
What is the normal bicarbonate level in the blood, what is this set by?
[HCO3-] =24 mM
-set by the kidney
What is the normal pCO2, what is this set by?
pCO2= 40 mmHg
-this is set by the lung
What is a metabolic line on the davenport graph?
family of curves which relate bicarbonate concentration to pH at a series of fixed PCO2 concentrations
What is a respiratory line on the davenport graph?
a line which represents the effect of pulmonary ventilation on blood pH and bicarbonate levels
What is TCO2 equal to?
[CO2] + [H2CO3]+[HCO3]
When HB is greater in the blood, what happens?
more HCO3- is produced per change in pH
What are some causes of hypoventilation?
- COPD -emphysema, asthma
- narcotics and anesthesia
- airway obstruction or lung collapse
- muscular dystrophy or paralysis
- pneumonia or bronchitis
- severe pulmonary edema
What is the normal pH of the blood?
7.4
During hypoventilation, or hypercapnea, what occurs to the pH? the bicarbonate level?
pH decreases - respiratory acidosis
bicarbonate increases
What is renal compensation for respiratory acidosis? Why is this strange?
reabsorption of HCO3-, excretion of H+
- so HCO3- is increased further to essentially raise the pH
- pH can rise or fall when HCO3- is inc
What is the main factor pH is determined by?
proton concentration (NOT HCO3-)
What are some causes of hyperventilation or hypocapnea?
- ventilator set too high
- anxiety attack
- trauma to the respiratory center
- brain tumor
As pCO2 is dec in respiratory alkalosis, what happens to the pH and HCO3-?
pH increases
HCO3- Decreases
Respiratory acidosis or alkalosis results in decreased cerebral blood flow?
respiratory alkalosis results in lightheadness and inability to concentrate (hyperventilate)
What is the renal compensation for respiratory alkalosis?
decrease HCO3- reabsorption (decreasing concentration even further) to decrease pH
-also dec excretion of titrable acids - NH4Cl
What are some examples of metabolic alkalosis causes that are responsive to saline infusion?
- vomiting and dehydration
- gastric tubes
- excess diuretics
What is an example of a cause of metabolic alkalosis that is unresponsive to saline infusion?
hyperaldosteronism
What is the renal response to metabolic alkalosis?
decrease reabsorption of HCO3-
ALKALOSIS always want to dec HCO3- absorption
What is the only acid/base disorder which renal compensation can completely normalize blood pH for?
respiratory alkalosis
Why do excess diuretics cause metabolic alkalosis?
-inc loss of NaCl and fluids
-inc RAA stimulation
-inc renal proton secretion
(aldosterone causes Na reabsorption, K secretion creating hypokalemia - so you want to reabsorb K, and have to get rid of H+ as a result)
What happens to the pH and HCO3- levels in metabolic acidosis?
pH decreases, HCO3- decreases
What is the formula for the anion gap, and what is a normal value?
=Na- (Cl+ Hco3) = 12+/-4
In diabetes mellitus, during ketoacidosis, what happens to the anion gap?
it is increased
What are some causes of metabolic acidosis?
- diabetic ketoacidosis
- lactic acid
- poisons
- methanol
- ethylene glycol
- aspirin overdose
Hypercholeremia:
- severe diarrhea
- uremias
What occurs during proximal renal tubular acidosis?
reabsorption of bicarbonate is decreased
-metabolic acidosis
What happens during distal renal tubular acidosis?
acid secretion is decreased
-metabolic acidosis
What is a base deficit?
amount of HCO3- that should be added to bring patient back to normal
actual [HCO3-]-24
