ABG

• Acid-Base Balance


  • Physiologic Buffers
  • Lungs
  • Kidneys
• Acid-Base Balance: Physiologic Buffers are the 1st line of defense, responding quickly to neutralize excess acids or bases
• Lungs are the 2nd line of defense, speeding up or slowing down respirations to adjust CO2 levels in the blood within 1-2 minutes
• Kidneys are the 3rd line of defense, excreting acid or base as needed in urine
• Homeostasis of H+ ion concentration


  Changes in this concentration can affect normal cell function
• Acid-Base Balance


  The correct balance of acidic and basic (alkaline) compounds in the blood
• Acidosis


  When the level of acid in the blood is too high
• Alkalosis


  When the blood becomes too alkaline
• Respiratory Acidosis


  • Occurs when the lungs cannot remove enough carbon dioxide from the body
• Common causes of Respiratory Acidosis

  • Airway diseases like COPD and asthma
  • Diseases affecting chest and breathing ability like scoliosis
  • Lung tissue diseases
  • Medicines that suppress breathing like narcotics
  • Severe obesity
  • Obstructive sleep apnea
  • Chest trauma
• Respiratory Acidosis: Hypoventilation


  • Tachycardia
  • Hypotension
  • Dysrhythmias
  • Anxiety
  • Irritability
  • Confusion
  • Lethargy
  • Headache
  • Decreased level of consciousness leading to coma
  • Ineffective, shallow respirations
  • Dyspnea
  • Pale, cyanotic skin
• Respiratory Alkalosis


  • Occurs when the carbon dioxide levels in the body drop too low, often due to hyperventilation
• Common causes of Respiratory Alkalosis

  • Anxiety
  • Acute respiratory distress
  • Congestive heart failure
  • Head trauma
  • Severe blood loss
  • Pneumonia
  • Salicylic (ASA) overdose
• Respiratory Alkalosis: Hyperventilation


  • Tachypnea
  • Tachycardia
  • Ventricular/atrial dysrhythmias
  • Inability to concentrate
  • Numbness
  • Tingling
  • Tinnitus
  • Loss of consciousness
  • Rapid, deep respirations
• Metabolic Acidosis


  • Kidney disease
  • Lactic acidosis
  • Diabetic acidosis
  • Severe dehydration
  • Severe diarrhea
• Metabolic Acidosis


  • Bradycardia
  • Weak peripheral pulses
  • Hypotension
  • Tachypnea
  • Headache
  • Drowsiness
  • Confusion
  • Rapid, deep respirations (Kussmaul respirations)
  • Warm, dry, pink skin
• Metabolic Alkalosis


  • Diuretic overuse
  • Excess vomiting
  • Antacids
  • Loss of potassium or sodium
  • Ingestion of bicarbonate
  • Alcohol abuse
  • Laxatives
  • Heart, kidney, or liver failure
• Metabolic Alkalosis


  • Tachycardia
  • Normal BP or hypotension
  • Atrial tachycardia
  • Ventricular issues
  • Anorexia
  • Nausea/vomiting
  • Decreased level of consciousness
  • Confusion
  • Headache
  • Numbness and tingling
  • Lethargy
  • Seizures
  • Slow, shallow respirations
  • Depressed skeletal muscles leading to ineffective breathing
• Interpreting ABGs


  1. Look at the pH to determine if there is acidosis or alkalosis

  2. Look at PCO2 and HCO3- to determine if the cause is respiratory or metabolic

  3. Look for compensation for the acid-base imbalance
• Robert has a pH of 7.26, PCO2 of 42, and HCO3- of 17, indicating metabolic acidosis with no compensation
• Luis has a pH of 7.26, PCO2 of 52, and HCO3- of 34, indicating respiratory acidosis with partial compensation
• Kate has a pH of 7.48, PCO2 of 51, and HCO3- of 39, indicating metabolic alkalosis with partial compensation