Acid + Base Flashcards
Normal plasma pH?
• ph range compatible with life?
7.35-7.45
ph range compatible with life=6.8-7.8 this represents a 10 fold difference in H+ conc in plasma (its logarithmic scale)
How do buffer systems work?
prevent major changes in pH by removing or releasing H+
- Can act quick to prevent excess H+ conc changes
- H+ buffered by intracellular and extracellular buffers
• The major extracellular buffer is
What ratio should be seen in this buffer?
the bicarbonate-carbonic acid buffer system
this is assessed when ABGs are measured
• There should be 20 parts bicarbonate (HCO3-) to one part carbonic acid (H2CO3) and if the ratio is altered ph changes. The ratio, not the values are important. A shift in either leads to imbalance
• Intracellular buffers include proteins
proteins, organic and inorganic phosphates, and (in RBCs) haemoglobin
how do kidneys buffer?
- Regulate bicarbonate level in ECF
- Can regulate bicarbonate ions and reabsorb them from renal tubular cells
- In resp acidosis and most cases of metb acidosis the kidneys excrete H+ and conserve bicarbonate ions to help restore balance
- In resp and metb alkalosis the kidneys retain H+ ions and excrete bicarbonate
When can the kidneys not compensate for metb acidosis?
when the acidosis is caused by kidney failure…
What part of the brain responds to changing acidity and how?
• The medulla controls the CO2 and therefore the carbonic acid content of ECF by adjusting ventilation in response to amount of CO2 in blood
What do you see in the blood with metb acidosis + alk?
- Metb acidosis is common and characterized by low PH (inc H+ conc) and low plasma bicarbonate conc
- Can be caused by gain of H+ or loss of bicarb
*Why are ABG’s measured?
To evaluate respiratory and renal function
A method to determine Acid-Base and electrolyte imbalances
*Where are ABG’s taken from?
Radial artery (most common) Brachial or Femoral artery Arterial line ( Artline)
*Nursing considerations for taking ABGs?
More painful procedure than regular blood test
Increased risk of bleeding
Increased risk of hematoma at puncture site
*ABG’s can also measure what?
- Electrolytes (sodium and potassium)
- Hemoglobin
- Glucose
- Lactate
*What Exactly Do ABG’s Measure
1) pH (The number of free H+ ions in the body)
2) PaCO2/PC02
3) PaO2/P02
4) HCO3-
5) BE
Base Excess (the amount of blood buffer that exists)
Low values indicate acidosis
High values indicate alkalosis
*What blood values indicate acidosis and alkalosis?
Less than 7.35 is considered acidosis
Greater than 7.45 considered alkalosis
*Normal PaCO2 levle?
Normal range 35 to 45 mm Hg
*Normal HCO3- level?
22-26mmol/L
Used to look at the metabolic side of acid-base balance
*Normal range of PaO2?
How does this change with age?
What value indicates hypoxemia?
80-100 mm Hg
There is a normal decline in pO2 of older adults
Below 60 indicates hypoxemia
*What are the causes of resp acidosis?
Any disease process or problem that cause impaired ventilation could potential cause respiratory acidosis
Examples: -Drug Overdose -Pneumonia -Pulmonary edema -Chest injuries Asthma COPD