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