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24 Cards in this Set
- Front
- Back
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Chemical Buffer Systems
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Systems that keep the pH relatively constant
Carbonic Acid - Bicarbonate Buffer System - primary the system that we monitor clinically maintains stable pH with 20 bicarbonate : 1 carbonic acid Phosphate Buffer System – secondary back-up Protein Buffer System – secondary back-up |
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Respiratory control
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makes changes quickly
pH decreases, more acid, rate and depth increases pH increases, more alkaline, rate and depth decreases |
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Renal regulation – days to weeks
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kidneys make permanent adjustments
when acidosis occurs, H+ excreted in urine when alkalosis occurs, HCO3 excreted in urine |
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pH
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pH
Measures the acidity or alkalinity of a solution Large number of H ions = decreased pH – acidic state Small number of H ions = increased pH – alkaline state Normal pH 7.35-7.45, lower indicates acidic state Normal PCO2 35-45, if higher indicates acidic state Normal HCO3 22-26, if lower indicates acidic state Acid - compound that gives up hydrogen Base - compound that combines with acids |
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Acidosis
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Abnormal increase in hydrogen ion concentration as a result of an accumulation of an acid or a loss of a base
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Alkalosis
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Abnormal condition caused by excess bicarbonate or deficiency of acid
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Ion
Electrically charged particle |
H+ - hydrogen
HCO3 - bicarbonate CO2 - carbon dioxide H2CO3 - carbonic acid |
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pH
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normal 7.35-7.45
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pCO2 or paCO2
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direct measurement of the partial pressure of CO2 in the blood
reflects the respiratory component normal 35-45 mm Hg |
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SaO2
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arterial oxygen saturation
normal 95-100% |
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pO2 or paO2
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partial pressure of oxygen dissolved in the blood
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HCO3
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bicarbonate ion
reflects the metabolic component of acid-base normal 22-26 mEq/L HCO3 (alkaline) causes the kidney to retain H+ HCO3 (acidic) causes the kidneys to excrete H+ |
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Base excess/base deficit
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reflects an increase or decrease in the total amount of base present
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Normal Arterial Blood Gas Interpretation
Acidotic |
You need only the CO2 and HCO3 along with the pH to interpret ABGs
pH < 7.35 CO2 > 45 HCO3 < 22 Compensation is occurring if pH is approaching the normal range, but pCO2 and/or HCO3 are out of balance Lungs will compensate if the primary imbalance is metabolic acid base Kidneys will compensate if the primary imbalance is respiratory COPD ICP |
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pH is 7.20
PCO2 is 56 HCO3 is 25 |
Look at the pH
The pH is 7.20 therefore it is acid. It is also uncompensated because the ph has not returned to normal. Look at the PCO2 The PCO2 is 56 so that is acid Look at the HCO3 The HCO3 is 25 which in within normal limits Look to see which of the components-resp or metabolic match the pH pH is acid PCO2 is acid. PCO2 is the respiratory component HCO3 is normal Interprete Uncompensated Respiratory acidosis |
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example
Ph is 7.68 PCO2 is 43 HCO3 is 35 |
Answer
Ph of 7.68 is uncompensated alkalosis PCO2 of 43 is normal HCO3 of 35 is alkalosis Patient has uncompensated metabolic alkalosis |
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example
pH is 7.38 PCO2 is 49 HCO3 is 30 |
Answer
pH of 7.38 is compensated acidosis PCO2 of 49 is acidosis HCO3 of 30 is alkalosis The patient has compensated respiratory acidosis |
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example
Ph is 7.54 PCO2 is 33 HCO3 is 33 |
Answer
pH of 7.54 is uncompensated alkalosis PCO2 of 33 is alkalosis HCO3 of 33 is alkalosis Patient has uncompensated respiratory and metabolic alkalosis |
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Respiratory Acidosis
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A carbonic acid excess resulting from any situation that decreases the rate of pulmonary ventilation
Etiology of Resp. Acidosis Damage to the resp center Obstruction to the resp. passage Loss of lung surface for ventilation Weakness of the resp. muscles Severe resp. depression |
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S/S of Resp. Acidois
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Important to recognize patients with inadequate ventilation early so interventions can be begun
Decrease pH and increased PCO2 Visual disturbances Headaches Confusion Drowsiness Coma Intervention for Resp. Acidosis Correct underlying problem to improve ventilation |
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Respiratory Alkalosis
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A carbonic acid deficit
Etiology of Resp. Alkalosis Caused by excessive pulmonary ventilation S/S of Resp. Alkalosis Increased pH and decreased PCO2 Lightheadedness Numbness and tingling of the fingers and toes Interventions for Resp. Alkalosis Treat underlying cause, often anxiety or pain |
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Metabolic Acidosis
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DKA A bicarbonate deficit that occurs when excess acids are added or bicarbonate is lost.
Etiology of Metabolic Acidosis Loss of bicarbonate-diarrhea, draining wounds Renal failure – most common Salicylate intoxication Starvation shock S/S of Metabolic Acidosis Decrease in pH and decrease in HCO3 Headache Mental dullness Kussmal respirations-rapid, deep respirations |
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Interventions for Metabolic Acidosis
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Sodium Bicarbonate
Dialysis |
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Metabolic Alkalosis
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Bicarbonate excess that occurs when excessive amounts of acid are lost from the body or when an increase amount of bicarbonate are added orally or IV
Etiology of Metabolic Alkalosis Loss of hydrochloric acid from the stomach Loss of K ions through diarrhea, fistulas Ingestion of large amounts of bicarbonate or other antacids Excessive administration of bicarbonate Diuretic therapy Mineralocorticoids S/S of Metabolic Alkalosis Increase in pH and increase in HCO3 Mental confusion Dizziness Numbness and tingling of toes and fingers Muscle twitching Tetany and seizures Treatment of Metabolic Alkalosis Treat the underlying problem Diamox-which will increase excretion of bicarbonate from the kidney |
