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65 Cards in this Set

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What is pH?
It is the power of hydrogen
Why do we care about pH?
-it represents the activity of H+ ions.
-pH decreases-H+ increases
-pH increases-H+ decreases
As H+ ion concentration increases, pH_____________
decreases
What are the types of acids produced by cellular metabolism?
-carbonic acid (H2CO3)
-metabolic acids (phosphoric acid H3PO4) & (sulfuric acid H2SO4)
pH of systemic arterial blood is normally slightly___________________
alkaline
What is the normal pH?
7.35-7.45
What are the 3 systems involved in acid‐base balance?
-bicarbonate buffer system
-respiratory system
-renal system
The bicarbonate buffer system, respiratory system, and renal system work together all the time to balance what?
pH
What is the function of an acid in maintaining acid‐base balance?
-fluid is alkaline
-acid releases H+
What is the function of a base in maintaining acid‐base balance?
-fluid is acidic
-base takes up H+
What is the most important system in maintaining pH?
bicarbonate buffer system
What are the main players in the bicarbonate buffer system?
-bicarbonate acid
-carbonic acid
What is the normal ratio of bicarbonate acid & carbonic acid required to maintain balance?
20:1 (HCO₃:H₂CO₃)
Be familiar with the reversible equation involving the combination of H+ with HCO3‐ to form carbonic acid (catalyzed by carbonic anhydrase)
H+ (+) HCO₃ <> H₂CO₃ > CO₂ + H₂O
-the equation can go either way depending if the conditions are acidic or alkaline
How does the equation H+ (+) HCO₃ <> H₂CO₃ > CO₂ + H₂O work in acidic conditions?
-hydrogen combines with bicarbonate acid to help neutralize the acid and increase the pH.
-anhydrase catalyzes carbonic acid to excrete water and carbon dioxide
How does the equation H₂CO₃ <> HCO₃ + H+ work in basic (alkaline) conditions?
-carbonic acid releases hydrogen
-trying to decrease pH
-getting back to balance
What systems are in place to excrete acid?
-respiratory system
-renal system
What is the respiratory contribution to acid-base balance? How fast does this happen?
-the lungs expire CO₂ and H₂O which is broken down from carbonic acid
-only takes seconds/minutes to respond
The lungs can only secrete which acid?
carbonic acid
Which receptors control the respiratory contribution to acid-base balance?
chemoreceptors
Baroreceptors sense the change in what?
-sense change in pressure
Chemoreceptors control what?
-rate & rhythm of respiration
How do chemoreceptors sense the pH?
through PaCO2 in the blood
The chemoreceptors sense changes in what?
H+
The osmoreceptors sense the change in what?
osmolality (concentration)
What is the best indicator of the lung's effectiveness in correcting carbonic acid (H₂CO₃) levels (ABG)?
PaCO₂
What does it mean to say that H₂O and CO₂ are volatile acids?
-carbonic acid must break down into H₂O & CO₂
-they are broken into gases and then excreted by the lungs
When PaCO₂ goes up, what happens to pH?
pH decreases
When PaCO₂ goes up, what happens to PaO₂?
PaO₂ decreases
What is the renal contribution to acid base balance? How quickly can it work?
-kidneys can excrete any acid but carbonic acid
-slow response (3-5 days)
What type of acids can the kidneys excrete?
metabolic acids
How does the kidney secrete acid?
-reabsorption of filtered HCO₃ as H+ secreted into renal tubular filtrate
-formation of titratable acid
excretion of NH₄ in urine
As H+ is secreted into the renal tubular filtration, ________ is reabsorbed?
HCO₃
Why can't H+ be secreted in its free form within urine?
it would damage the renal tubular cells of the kidneys. instead it is excreted in a buffer form attached to NH₃.
How is H+ secreted in the renal system?
-HCO₃ moves through nephron
-H+ is secreted
-H+ is only secreted after HCO₃ is reabsorbed
-H+ is buffered with NH₃
Why is NH₄ guaranteed to be excreted within urine?
it is lipid soluble and will not go back into kidney tubules easily.
What is the best indicator of the kidney's effectiveness for excretion of metabolic acids (ABG report)?
HCO₃
What is the response of the Buffer System to maintain acid-base balance?
-Buffers: low pH=basic portion of buffer accepts H+. high pH=acidic portion of buffer releases H+.
What is the response of the Respiratory System to maintain acid-base balance?
-Respiratory System: low pH= increased RR to remove carbonic acid. high pH=decreased RR to retain carbonic acid
What is the response of the Renal System to maintain acid-base balance?
-Renal System: low pH=increased secretion of H+ from ECF into renal tubular fluid. increased reabsorption of HCO₃ from renal tubular fluid back to ECF. increased production of NH₃. high pH= decreased secretion of H+. decreased reabsorption of HCO₃. decreased production of NH₃.
What is correction in acid-base balance?
correction of the imbalance occurs when the original problem (cause) is fixed within that system.
What is compensation in acid-base balance?
compensation of the imbalance does not fix the problem, but can restore the imbalance to normal
When the acid-base imbalance is within one system, how does compensation occur?
when the imbalance is offset in one system, the other system kicks in to compensate.
What acid-base imbalance is associated with diarrhea?
probably acidosis bc intestinal fluids are rich in bicarbonate. loss of bicarbonate leads to diarrhea.
What acid-base imbalance is associated with vomiting?
probably alkalosis bc stomach acids are acidic. loss of that would create alkalosis.
What is it when too much carbonic acid accumulates in the blood (increase PaCO₂)?
respiratory acidosis
What might cause respiratory acidosis?
anything that decreases ventilation or respiration (ex.Rt HF)
Why is respiratory acidosis dangerous for the brain?
-excess CO₂ enters the brain cells, leading to intracellular acidosis
-cerebral vasoconstriction (decreases blood flow)
-CNS depression (lethargy/disoriented)
-HA/blurred vision
-tachycardia
What do the kidneys do to help compensate for respiratory acidosis?
-excreting more metabolic acid
-causes increased HCO₃ in serum
-takes 3-5 days (slow process)
How can respiratory acidosis be corrected?
therapy required to restore metabolic balance. lactate solution used in therapy is converted to bicarbonate ions in the liver.
What is respiratory alkalosis?
not enough carbonic acid in blood (decreased PaCO₂)
What causes respiratory alkalosis?
anything that causes hyperventilation can lead to decreased carbonic acid.
Why do patients exhibit lightheadedness & mm cramps in respiratory alkalosis?
because the CSF becomes alkaline
What do the kidneys do to compensate with respiratory alkalosis?
kidneys conserve H+ & eliminate the HCO₃ in the urine.
How can respiratory alkalosis be corrected?
HCO₃ are replaced by Cl-
What is metabolic acidosis?
too much metabolic acid, due to gain of acid or loss of base
What might cause metabolic acidosis?
-intake of acids or substances converted to acids
-increased rate of metabolism
-production of unusual acids secondary to altered normal processes
-decreased renal excretion of acid
-HCO₃ can be lost in urine or through GI tract (vomit/diarrhea)
Why is metabolic acidosis dangerous to the brain?
decreased pH of CSF can lead to
-HA
-abdominal pain
-lead to coma
What do the lungs do to compensate with metabolic acidosis?
hyperventilate to excrete carbonic acid
How can metabolic acidosis be corrected?
lactate solution used in therapy is converted to bicarbonate ions in the liver
What is metabolic alkalosis?
too little metabolic acid, from loss of acid or gain of base
What might cause metabolic alkalosis?
-acid can be lost to urine & GI tract
-acid can be moved into cells to decrease levels in blood
Why is the onset of metabolic alkalosis symptoms slower?
bicarbonate ion cross membranes slower than CO₂
What do the lungs do to compensate with metabolic alkalosis?
decrease RR to retain carbonic acid
How can metabolic alkalosis be corrected?
restoring renal function