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[H+]
hydrogen ion concentration
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body fluid pH
7 10^-7 .0000001 mg/l
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lower pH
more acidic ([H+] high)
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Higher pH
more basic ([H+] low)
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body acids
formed as end products of metabolism
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Volatile body acids
can be eliminated as CO2 gas (carbonic acid h2co3 -> h2o+co2)
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Nonvolatile body acids
can be eliminated by kidney ( sulpuric, phosporic, organic acids secreted in urine)
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Buffers
- occur in response to acid base status
- Absorb excessive hydrogen or hydroxyl ion to prevent significant changes in pH
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Carbonic Acid-Bicarbonate Buffering
- Operates in lungs and kidneys
- lungs h2co3>h2o+co2
- kidneys h2c03>h+hco3
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Protein buffering
- intracellular buffer system
- Hemoglobin attaches to hydrogen and releases when needed for pH
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Renal Buffering
secrete hydrogen into urine and reabsorb bicarbonate
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Normal and abnormal pH levels
- 7.35-7.45
- death <6.9 or 7.8<
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PaCO2 normal
Arterial CO2 partial pressure: normal 35-45 mmHg
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Acidemia
- too much acid pH< normal 7.35
- systemic increase in [H+] is acidosis
- respiratory acidosis: excess co2
- Metabolic acidosis: loss of HCO3-
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alkalemia
- Too much base; pH > normal 7.45
- systemic decrease in [H+] is alkalois
- metabolic alkalosis: excess HCO3-
- Respiratory alkalosis: loss of CO2
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Compensation
- body adjustments to maintain normal pH
- resp compensates by changing ventiliation (increase/decrease CO2)
- Renal compensates by changing urine pH (takes days)
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Respiratory Acidosis
- breathing rate doesnt get rid of all CO2 resulting in hypercapnia
- COPD, drug overdose, head injury, pulmonary edema
- s&s: High PaCO2, high HCO3-, low pH, headache blurred vision breathlessness, restlessness, coma
- Compensation: kidney conserves HCO3- and eliminates H+
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Metabolic acidosis
- causes: loss of metabolic base (HCO3-) (diarrhea), or gain of acid (starvation, alcoholism, diabetes)
- S&s: low HCO3-, low PaCO2, low pH, headache confusion coma n&v
- Compensation: faster resp rate to blow of CO2
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Respiratory Alkalosis
- Causes: excessive reduction in CO2 levels (hyperventilation, Hypoxemia (altitudes), Brain stem over stimulation
- s&s: low PaCO2, low HCo3-, pH high, diaphoresis, dizziness, tingling coma
- compensation: kidney conserves H+ and excretes HCO3-
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Metabolic alkalosis
- Causes: loss of metabolic acid (emesis, gastric suctioning) or gain of metabolic base (excess antacid ingestion, diuretic therapy causing hypokalemia shifting H+ into cells)
- S&s: High HCO3-, high PaCO2, high pH neuromuscular irritibility, coma, + signs of causal cond
- Compensation: lungs "save" CO2 to offset increased base (slow breathing)
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mixed acid base imblance
- seriously ill
- ex: resp acidosis from bacterial pneumonia combined wit severe diarrhea metabolic acidosis
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Process
- Define (pH, PaCO2, HCO3-) acidotic, alkalotic or normal
- Determine what type (respiratory PaCO2 matches pH, Metabolic HCO3- Matches pH)
- Does either PaCO2 or HCO3- go the opposite direction of pH (yes compensated, no uncompensated
- PaO2 below limits hypoxemia
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