Acid-Base Disorders Flashcards
Normal arterial pH
7.34-7.45
Acid-base balance is normally maintained by
Lungs
Kidneys
pH level considered to be incompatible with life
Less than 6.7
Greater than 7.7
Buffering
Ability of weak acid and corresponding anion (base) to resist change in pH of a solution on the addition of a strong acid or base
Principal extracellular buffer
Carbonic acid/bicarbonate
H2CO3/HCO3- system
Other physiologic buffers
Plasma proteins
Hgb
Phosphates
Lungs regulate _____ and kidneys regulate _____
Lungs control CO2 + H2O
Kidneys control HCO3- + H+
Bicarb buffer system is most important b/c…
– More bicarbonate in the ECF than any other
buffer
– Unlimited supply of CO2
– Degree of ECF acidity can be regulated by changing HCO3- and/or pCO2
Carbonic Acid
– respiratory component of the buffer pair
– nearly all carbonic acid in the body exists as carbon dioxide (CO2) gas
– concentration directly proportional to the partial pressure of carbon dioxide (pCO2) and is determined by ventilation
Bicarbonate
– metabolic component
– kidneys regulate bicarbonate concentration
bicarbonate reabsorption occurs in
proximal tubule
bicarbonate reabsorption is catalyzed by
carbonic anhydrase
Remaining H+ secretion occurs in
distal tubule
Acid/Base Compensatory Mechanisms
– Compensation involves the opposite physiologic system as the primary disorder
– Primary disorder = respiratory ; kidneys compensate by adjusting HCO3- elimination
– Primary disorder = metabolic; lungs compensate by adjusting CO2 elimination
Assessment of Acid-Base Status
Blood Gas
Serum Electrolytes
– Useful to delineate respiratory vs metabolic disorder (HCO3-)
Medication/Medical History
– Current medications and disease processes
Most important diagnostic test for acid-base status
Arterial Blood Gas