nursing acid-base pH balance
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- normal pH
- pH 7.35-7.45
- most common buffer system
- CO2 + H2O --- H2CO3 --- H+ + HCO3-
- normal ratio of carbonic acid to bicarbonate
- 1:20
- respiratory acidosis
- Increased CO2 results in decrease in pH
- respiratory alkalosis
- Decreased CO2 results in increase in pH
- respiratory component of acid-base balance
- CO2 (carbon dioxide)
- metabolic acidosis
- Increased HCO3 results in increase in pH
- metabolic alkalosis
- Decreased HCO3 results in decrease in pH
- metabolic component of acid-base balance
- HCO3 (bicarbonate)
- normal PaCO2
- 35-45 mmHg
- normal PaO2
- 83-100 mmHg
- normal HCO3
- 22-26 mEq/L
- ABG analysis step 1
-
if pH is <7.35, acidosis
if pH is >7.45, alkalosis - ABG analysis step 2
-
if CO2 is abnormal, respiratory
if HCO3 is abornmal, metabolic - ABG analysis step 3
-
pH is normal: fully compensated
pH & opposite number out of range: partially compensated
pH out of normal range, opposite number in normal range: no compensation - oxyhemoglobin curve
- changes in pH alter ease with with hemoglobin releases O2 to plasma
- values of metabolic acidosis
- pH is low, HCO3 is low
- values of metabolic alkalosis
- pH is high, HCO3 is high
- values of respiratory acidosis
- pH is low, PaCO2 is high
- values of respiratory alkalosis
- pH is high, PaCO2 is low
- causes of metabolic acidosis
- diabetic ketoacidosis, starvation, lactic acidosis, excess ETOH or ASA, renal failure, diarrhea
- s/s of metabolic acidosis
- lethargy, confusion, stupor, coma, hyporeflexia, muscle weakness, bradycardia, thready pulses, low BP, Kussmaul resp, warm/flushed/dry skin, hyperkalemia
- treatment of metabolic acidosis
- treat the cause: insulin, hydration/electrolytes, antidiarrheals, sodium bicarbonate, dialysis
- causes of metabolic alkalosis
- antacid overuse, IV LR overuse, NaHCO3 overuse, vomiting, NG suctioning, thiazide diuretics
- s/s of metabolic alkalosis
- anxiety, irritability, hyperreflexia, muscle cramps/weakness, tachycardia, normal or low BP, shallow resps, hypokalemia, hypocalcemia
- treatment of metabolic alkalosis
- treat the cause: fluid/electrolyte replacement, NS IV, Ca++, K-sparing diuretics, antiemetics
- causes of respiratory acidosis
- head injury, Rx overdose, chest injury, electrolyte imbalance, severe obesity, ascites, hemothorax, COPD, aspiration, pneumonia, pulm edema, TB, PE
- s/s of respiratory acidosis
- skin pale to cyanotic & dry, incr. PaCO2
- treatment of respiratory acidosis
- increase CO2 excretion: bronchodilators, steroids, Mucomyst, O2, pulmonary hygiene, PAP
- causes of respiratory alkalosis
- hyperventilation - anxiety, fear, mechanical ventilation; hypoxemia - asphyxiation, shock, high altitude
- s/s of respiratory alkalosis
- numbness & tingling around mouth, extremities, resp. effort normal or incr.
- treatment of respiratory alkalosis
- treat underlying condition, support renal function w/ fluids, breath into bag or rebreather, sedatives