2) Examples of Arterial Blood Gases

Where is arterial blood typically drawn from to measure blood gases?

Radial artery, brachial artery, femoral artery

What is the normal pH range for arterial blood?

7.35 – 7.45

Which of the following is the normal arterial partial pressure of CO₂ (PaCO₂)?

4.7 – 6.0 kPa

What is the typical range for arterial oxygen (PaO₂) on room air?

10–13 kPa

In metabolic acidosis, which of the following changes is typically observed?

Decreased pH and decreased bicarbonate

What is the primary compensatory mechanism in metabolic acidosis?

Hyperventilation to reduce PaCO₂

A patient has a pH of 7.20, low bicarbonate, and low CO₂. What is the diagnosis?

Metabolic acidosis with respiratory compensation

Why might lactate be elevated in a patient with severe blood loss?

Anaerobic metabolism due to hypoperfusion

In an opiate overdose, which acid-base disturbance is most likely?

Respiratory acidosis due to hypoventilation

A patient overdosed on morphine and has pH 7.20, normal HCO₃⁻, and high PaCO₂. What explains the normal bicarbonate?

Renal compensation has not had time to occur

Why is bicarbonate unchanged in early respiratory acidosis?

The kidneys have not yet responded

What is the initial step in interpreting an arterial blood gas (ABG)?

Examine the pH

What is the main cause of acidosis in opiate overdose?

Decreased CO₂ elimination