Week 9 - Acid Base and Electrolyte Balance

Question 1

Define ABG Interpretation (Arterial Blood Gas)

Answer 1

ABG interpretation involves assessing pH, PaCO₂, and HCO₃ to identify if the imbalance is respiratory or metabolic, and whether it’s acidosis or alkalosis.
Example:
- pH < 7.35 = acidosis
- pH > 7.45 = alkalosis
- PaCO₂ = respiratory component (↑ = acidosis, ↓ = alkalosis)
- HCO₃⁻ = metabolic component (↓ = acidosis, ↑ = alkalosis)

Question 2

Define Acidosis

Answer 2

A systemic increase in hydrogen ion concentration.

Question 3

Define Acidaemia

Answer 3

The pH of arterial blood is less than 7.35

Question 4

Define Alkalosis

Answer 4

A systemic decrease in hydrogen ion concentration.

Question 5

Define Alkalaemia

Answer 5

The pH of arterial blood is greater than 7.45

Question 6

Define Acid-Base Imbalance of Respiratory Acidosis

Answer 6

Cause:
- Hypoventilation → CO₂ retention
- ↑ PaCO₂, ↓ pH

Underlying mechanism:
- Excess CO₂ combines with water to form carbonic acid → lowers pH

Common causes:
- COPD
- Respiratory depression
- Airway obstruction

Compensation:
- Kidneys retain HCO₃⁻ to buffer the acid

Signs:
- Confusion
- Drowsiness
- Headache
- Hypoxia

Question 7

Define Acid-Base Imbalance of Respiratory Alkalosis

Answer 7

Cause:
- Hyperventilation → CO₂ loss
- ↓ PaCO₂, ↑ pH

Mechanism:
- Less CO₂ = less carbonic acid → raises pH

Common causes:
- Anxiety
- Pain
- Fever
- Hypoxia

Compensation:
- Kidneys excrete HCO₃⁻

Signs:
- Lightheadedness
- Tingling
- Muscle cramps

Question 8

Define Acid-Base Imbalance of Metabolic Acidosis

Answer 8

Cause:
- ↑ acid production or HCO₃⁻ loss
- ↓ HCO₃⁻, ↓ pH

Mechanism:
- Excess hydrogen ions or loss of base (e.g., in diarrhea, renal failure, DKA)

Compensation:
- Lungs increase ventilation to blow off CO₂

Signs:
- Kussmaul respirations
- Hypotension
- Confusion

Question 9

Define Acid-Base Imbalance of Metabolic Alkalosis

Answer 9

Cause:
- ↑ HCO₃⁻ or H⁺ loss
- ↑ HCO₃⁻, ↑ pH

Mechanism:
- Loss of acid (e.g., vomiting, diuretics) or excessive antacid use

Compensation:
- Lungs retain CO₂ (hypoventilation)

Signs:
- Hypoventilation
- Muscle cramps
- Arrhythmias

Question 10

What are the two organs responsible for Acid-Base Regulation

Answer 10

1. Lungs (Short-Term Regulation)
   - Regulate CO₂ levels via ventilation
   - Respond within minutes to hours
2. Kidneys (Long-Term Regulation)
   - Regulate H⁺ excretion and HCO₃⁻ reabsorption
   - Respond over hours to days