Acid-Base Balance and Disturbances Flashcards
Steps to determining Acid-Base status:
1) from value of pH determine whether the patient is acidotic or alkalotic
2) From values of PaCO2 and HCO3-, determine primary disturbance, whether resp (it is resp if change in PaCO2 is compatible with change in pH) or metabolic (if the change in HCO3- is compatible with the change in pH)
3) From the values of PaCO2 and HCO3-, determine of a compensatory response has occurred
4) normal pH is 7.35-7.45, normal HCO3- is 22-27mEq/L, normal PaCO2 is 35-45 mmHg
pH is determined by the ratio of _____ to _____.
HCO3- to PaCO2
Name two acid base disturbances that can be COMPLETELY compensated.
1) respiratory acidosis
2) respiratory alkalosis
Can complete compensation be achieved if there is metabolic acidosis or metabolic alkalosis?
No
If an acid base disturbance is completely compensated, it is a _______ disturbance.
respiratory disturbance
________ disturbances are a decrease/increase in blood H+ concentration caused by the addition of bases or acids to/from body fluids.
metabolic
________ disturbances are an increase or decrease of blood H+ concentration caused by hypoventilation or hyperventilation leading to either CO2 retention or loss.
respiratory
pH= 7.48, HCO3-=38, PaCO2=53
partially compensated metabolic alkalosis
pH= 7.37, HCO3-=36, PaCO2=65
compensated respiratory acidosis
pH= 7.32, HCO3-=32, PaCO2=65
partially compensated respiratory acidosis
What is the underlying mechanism of bicarbonate ion reabsorption?
Na-H+ exchange
_______ is a diuretic that works by inhibiting carbonic anhydrase, that ultimately inhibits reabsorption of Na and bicarbonate.
acetazolamide (diamox)
______% of the filtered HCO3- is reabsorbed in the proximal tubule.
90%; the 10% that escapes reabsorption in the proximal tubule gets reabsorbed in later segments; HCO3- is not normally excreted
____ is actively secreted into the lumen of the proximal tubule in exchange for _____, which enters the cell passively.
H+; Na+
The kidneys produce _____ by excreting acids.
HCO3-; the H+-Na+ exchange is the key step in this process
______ and _______ are the acids excreted by the kidneys.
titratable acids and ammonia (NH3)
*NH3 enters tubular lumen and reacts with H+ to form ammonium NH4–> very poorly penetrates cell membranes–> remains trapped in tubular lumen and is excreted–> process is called diffusion trapping
What is the formula for Anion gap?
Na-Cl+HCO3=anion gap
can also be manipulated;
ex) HCO3= Na-Cl-anion gap
With potassium
The anion gap is calculated by subtracting the serum concentrations of chloride and bicarbonate (anions) from the concentrations of sodium and potassium (cations):
= ([Na+] + [K+]) − ([Cl−] + [HCO3−])
Without potassium (daily practice) Omission of potassium has become widely accepted, as potassium concentrations, being very low, usually have little effect on the calculated gap. This leaves the following equation:
= [Na+] − ([Cl-] + [HCO3−]) =16 meq/lit
What is the normal anion gap range?
~8-16mEq/L; sweat book says 10-12
What is the utility of the anion gap?
the measurement of unmeasured anions= the “gap” (HPO4, SO4, etc); useful for the differential diagnosis of metabolic acidosis
With an anion gap of 20-29, the diagnosis is ________ 67% of the time.
metabolic acidosis
What is urine volume and osmolality when ADH release is inhibited?
osmolality low; Volume Large–> it gets inhibited because the bodys volume is TOO dilute and large…. needs to get rid of it by diuresis
How does aldosterone affect sodium and potassium excretion?
Sodium excretion DECREASED and potassium excretion INCREASED
What diuretic works by inhibiting the Na-K-Cl symporter?
furosemide (lasix)
Spironolactone primarily works on what part of the renal tubule?
collecting duct
