Acid-Base Balance and Disturbances Flashcards Preview

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Flashcards in Acid-Base Balance and Disturbances Deck (30)
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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?



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.



________ disturbances are an increase or decrease of blood H+ concentration caused by hypoventilation or hyperventilation leading to either CO2 retention or loss.



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


The chronic renal failure patient has a tendency for increased bleeding, in part because of the production of defective _______.

von Willebrand's factor


Blood pressure in the individual at rest is controlled primarily by _______.



Which combination of acute electrolyte abnormalities will most stabilize nerve, skeletal muscle, and cardiac ventricular cells?

hypokalemia and hypercalcemia


A clinically appropriate K+ concentration for cardioplegia solution is ______mEq/L.



Which of the following is an important stimulus for aldosterone release from the adrenal cortex?
1) high serum Na
2) high serum K+
3) low levels of ADH
4) low serum K+

2) high serum K+--> aldosterone secretes more K+ to be excreted


What hormone controls ECF VOLUME, and what hormone controls ECF sodium concentration?

Answer from Scott: The answers hinge on a couple of key words in each question … ADH
(vasopressin) adjusts sodium *concentration* by altering water reabsorption in the kidney. Recall that concentration is Amount/Volume, so by adjusting body water volume via AHD at the kidneys, the ADH ultimately
adjusts sodium concentration.

Aldosterone, by altering the *amount* of sodium ind the body, adjusts TBW via osmosis—“where sodium goes, water follows.”

In “real life” both hormones are working simultaneously to constantly adjust sodium concentration and sodium amount, but when questions on which hormone most effects concentration versus volume, go with the
relationships above.