Acid-Base Balance Flashcards
Regulators of Acid-Base Balance
-Buffers
- Primary regulators
- Act immediately (within 1 second of abnormal pH)
- Combine w/ acids or base to prevent pH changes (Examples include: Carbonic acid-sodium-bicarbonate, protein & phosphate buffering systems)
Regulators of Acid-Base Balance
-Resp system
- Responds within minutes to hours to changes in acid/base to eliminate or retain CO2.
- Respiratory center in medulla controls breathing
- Increased respirations leads to increased CO2 eliminated from body + decreased CO2 in blood
- Decreased respirations leads to decreased CO2 elimination from body + increased CO2 in blood
Regulators of Acid-Base Balance
-Renal system
- Responds within hours to days (last line of defense; may take hours or days to restore normal hydrogen ion concentration)
- Secretes hydrogen (H+) ions + reabsorbs bicarbonate (HCO3) ions
- Reabsorption + secretion of electrolytes (e.g., Na, Cl)
Acid-Base Balance
-pH
- Measures hydrogen ion concentration in body fluids
- Body maintains a slightly alkaline pH of 7.35-7.45
- Metabolic and respiratory processes work together to keep H+ levels within a normal range
- Increase in H+ makes solution more acidic
- Decrease in H+ makes solution more alkaline
Acid-Base Balance
-PaCO2
- Partial pressure of CO2 in arterial blood
- Reflection of depth of pulmonary ventilation
- Normal range is 35-45 mmHg
Acid-Base Balance
-PaO2
- Partial pressure of O2 in arterial blood
- No primary role in acid-base balance regulation if within normal limits
- Normal range is 80-100 mmHg
- Hypoxemia may cause
-anaerobic metabolism
-hyperventilation
Acid-Base Balance
-Oxygen saturation
- Percentage of Hgb saturated by oxygen
- Normal value is 95-100%
- If PaO2 drops below 60 mmHg, then will see a large drop in saturation
Acid-Base Balance
-Base excess
- Amount of blood buffer that exists
- Normal value is +/- 2
-Base Excess
-Base Deficit
Acid-Base Balance
-Bicarbonate
- Major renal component of acid-base balance
- Excreted + reproduced by the kidneys to maintain normal acid-base
- Principle buffer of extracellular fluids in the body
- Normal range is 22-26 mEq/L
Acid-Base Balance
-Anion gap
- Reflection of anions, not routinely measured
- Normal range is 12 mEq/L (+/-2)
- Increase: Seen with lactic acidosis or ketoacidosis
- Normal: Usually caused by loss of bicarb (i.e. diarrhea, diuretics)
Summary (via professor google)
* AG = (Na+ + K+) - (HCO3 + Cl-)
-w/ potassium given
w/o potassium given, eliminate K+
* Unmeasured anions
* HCO3 decrease is acidosis, but sometimes Chloride increases to maintain anion gap
How to obtain Arterial Blood Gases
- Heparinized syringe
- Blood from an artery
- Make sure at least 15-20 minutes have passed after procedures
- Apply pressure for 5 minutes
- On ice
- Prompt delivery to lab
Acid-Base Balance
-ABG norm values
- pH 7.35-7.45 (7.4)
- PaCO2 35-45 mmHg (acid)
- HCO3 22-26 mEq/L (base)
- PaO2 80-100 mmHg (partial pressure of oxygen in arterial blood)
- SaO2 96-100% (arterial saturation)
Interpretation of ABGs
-Dx in 6 steps
1-Analyze pH
2-Analyze PaCO2
3-Analyze HCO3
4-Determine if PaCO2 or HCO3 matches alteration
5-Compensation?
6-Analyze PaO2 and SaO2
ROME
Respiratory
Opposite
-Alkalosis ↑ pH ↓ PaCO2
-Acidosis ↓ pH ↑ PaCO2
Metabolic
Equal
-Acidosis ↓ pH↓ HCO3
-Alkalosis ↑ pH↑ HCO3
If both respiratory and metabolic components match the pH, maybe it is a _.
If both respiratory and metabolic components match the pH, maybe it is a mixed disorder.
Degree of compensation
-Absent
- pH is not within normal range
- The component that does not match the pH imbalance is still within its normal range
Degree of compensation
-Partial
- pH is not within normal range
- The component that does not match the pH disorder is above or below the normal range
Degree of compensation
-Complete
- pH is within the normal range
- Both components are either above or below normal range