Arterial Blood Gases

Indentify a patient’s : ◦ Oxygenation◦ Adequacy of gas exchange in the lungs◦ Acid-base status◦ Body’s ability to regulate pH◦ Underlying cause of the imbalance

ABG’s are used to

Direct arterial puncture Arterial line

How do we draw ABGs?

pH: 7.35-7.45- normal level PaO2: 80-100-normal level SaO2: 92%-100%- normal level CO2: 35-45- normal level HCO3: 22-26- normal level Base excess: + or – 2 – normal level

What will the ABGs show?

Measures the hydrogen ion concentration in the body fluids.

pH

The partial pressure of carbon dioxide in arterial blood and is a reflection of the depth of pulmonary ventilation.

PaCO2

Partial pressure of oxygen in arterial blood. PaO2 less than 60 leads to anaerobic

metabolism, resulting in lactic acid production and metabolic acidosis.

PaO2

Saturation is the point at which hemoglobin is saturated by oxygen.

Oxygen Saturation

Amount of blood buffer that exists (hemoglobin and bicarbonate)

High Value (Alkalosis) Low Value (Acidosis)

Base Excess

Major renal component of acid-base balance Kidneys excrete and retain bicarb to

maintain a normal acid-base environment.

Bicarbonate

Look at each number individually and label Evaluate Oxygenation Determine Acid-Base Status Determine whether Primary Acid-Base

Disorder is Respiratory or Metabolic Determine whether any form of

compensation response has occurred

How to interpret ABGs

Respiratory Acidosis: CO2 is high and pH is low

Respiratory Alkalosis: CO2 is low and pH is high

Metabolic Acidosis: HCO3 is low and pH is low

Metabolic Alkalosis: HCO3 is high and pH is high

4 possible Acid-Base Imbalances

Respiratory

Opposite

Metabolic

Equal

HINT

pH : 7.20 CO2: 52 pO2: 66 O2 sat..: 89% HCO3: 24

Step by Step!

Practice 1

pH: 7.58 CO2: 39 pO2: 81 O2 sat: 93% HCO3: 31

Step by Step!

Practice 2

Hypoventilation CNS depression Trauma COPD Acute airway obstruction

Causes of Respiratory Acidosis

Drowsiness, disorientation, dizziness, headache

Low BP Hypoventilation with hypoxia

Clinical manifestations of Respiratory Acidosis

Anxiety, fear Pain Fever Stimulants Excessive ventilatory support

Causes of Respiratory Alkalosis

Lethargy, light-headedness, confusion Tachycardia Hyperventilation

Clinical Manifestations of Respiratory Alkalosis

DKA Renal Failure Lactic Acidosis Drug overdose

Diarrhea

Causes of Metabolic Acidosis

Low BP Warm, flushed skin Nausea, vomiting Deep, rapid respirations

Clinical manifestations of Metabolic Acidosis

Excess ingestion of antacids Excess administration of sodium

bicarbonate

Vomiting Nasogastric Suctioning

Causes of Metabolic Alkalosis

Dizziness, irritability, nervousness, confusion

Tachycardia Muscle cramps

Clinical Manifestations of Metabolic Alkalosis

Let’s practice a few more problems.

Questions?