9/8- Intro to Acid Base Disturbances Flashcards
Normal values for arterial blood:
Normal values for venous blood:
What are the main sources for acid in the body?
- Diet (20 mmol H/day)
- Metabolism (H as nonvolatile acids 40 mmol/day)
How much acid is excreted per day?
About 70 mmol H+ is excreted in the urine/day
How is pH regulated (constantly)?
Buffers
- Absorb hydrogen ions when in excess and can release if depleted
What is the largest buffering system? Others?
Largest = bicarbonate
- Bicarbonate content can be regulated by the kidney and respiratory drive
Others: phosphates, proteins, hemoglobin…
Bicarbonate buffer system equation
Addition of acid leads to low levels of what?
Bicarbonate
What is the Henderson Hasselbach equation for bicarbonate buffer system?
- Typically pH and pCO2 are measured from arterial stick and then HCO3- is calculated
What are the cardinal acid base disorders and what can cause them?
- Metabolic acidosis (addition of acid, loss of bicarbonate)
- Metabolic alkalosis (addition of alkali, loss of acid)
- Respiratory acidosis (retention of CO2/ventilatory failure)
- Respiratory alkalosis (loss of CO2/hyperventilation)
Note: PCO2 levels from ventilation/respiratory compensation is always in the same direction as HCO3 (high acid accumulation with low HCO3 levels means PCO2 must be lowered as well, with hyperventilation.. and vice versa)
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How does the kidney compensate for accumulated PCO2?
Increased bicarbonate (HCO3) retention
What is the diagnosis (metabolic/respiratory acidosis/alkalosis) for:
- Arterial pH = 7.20
- HCO3- = 14 meq/L
- pCO2 = 30 mmHg
Metabolic acidosis (plug into H-H)
What is the diagnosis for:
- Arterial pH = 7.42
- HCO3- = 35 meq/L
- pCO2 = 60 mmHg
A. Metabolic acidosis
B. No disturbance
C. Metabolic acidosis and respiratory acidosis
D. Metabolic alkalosis and respiratory acidosis
Have normal pH but abnormal values (think mixed disorders)
- Always start with pCO2; it is high, so respiratory acidosis
D. Metabolic alkalosis and respiratory acidosis
How does the kidney handle H and HCO3?
- Proximal acidification
- Titrable acids and ammonia
- Distal acidification
Proximal acidification:
- Bicarbonate reabsorption
- No acid excretion
Titrable acids and ammonia:
- Acid excreted
Distal acidification:
- Acid excreted