Hypoxia

• Hypoxia


  Lack of oxygen reaching the tissues
• Anesthesia providers make every effort to avoid hypoxemia because of the irreversible damage to the myocardium, brain, and other end organs
• Despite these efforts, hypoxemia continues to occur in the operating room at a high rate
• Hypoxemia is one of the patient's most serious risks during anesthesia and surgical care
• Pulse oximetry


  An essential component of operating room technology to detect, treat, and reduce the degree of intraoperative hypoxemia
• Before the widespread of pulse oximetry in the 1980s and the establishment of anesthesia monitoring standards in the 1990s, hypoxemia was the leading cause of anesthesia-related mortality, since then, anesthesia-related mortality has dropped nearly 20-fold
• Causes of hypoxia during anesthesia - ABCDE

  • Airway
  • Breathing
  • Circulation
  • Drugs
  • Equipment
• Airway


  1. Obstructed airway prevents oxygen reaching lungs

  2. Tracheal tube misplaced

  3. Aspirated vomit blocks airway
• Breathing


  1. Inadequate breathing prevents oxygen reaching alveoli

  2. Severe bronchospasm prevents oxygen and CO2 exchange

  3. Pneumothorax causes lung collapse

  4. High spinal anesthesia causes inadequate breathing
• Circulation


  1. Circulatory failure prevents oxygen transport to tissues

  2. Causes include hypovolemia, abnormal heart rhythm, or cardiac failure
• Drugs


  1. Deep anesthesia depresses breathing and circulation

  2. Anesthetic drugs cause drop in blood pressure

  3. Muscle relaxants paralyze respiratory muscles

  4. Anaphylaxis causes bronchospasm and low cardiac output
• Equipment


  Problems with breathing circuit, oxygen supply, or monitoring equipment
• Management of hypoxia


  1. Check airway - signs of laryngospasm, vomit/blood

  2. Check breathing - chest movements, air entry, breath sounds

  3. Check circulation - pulse, blood pressure, perfusion

  4. Check drug effects - anesthesia depth, muscle relaxants, opioids

  5. Check equipment - oxygen delivery, breathing circuit, monitors
• Airway obstruction is the most common cause of hypoxia in theatre
• Unrecognized inadvertent esophageal intubation is a major cause of anesthesia morbidity and mortality
• An intubated patient who has been previously well-saturated may become hypoxic if the tracheal tube becomes displaced, kinked, or obstructed by secretions
• Bronchospasm, lung consolidation/collapse, lung trauma, pulmonary edema or pneumothorax may prevent oxygen from getting into the alveoli to combine with hemoglobin
• Drugs such as opioids, poorly reversed neuromuscular blocking agents or deep volatile anesthesia may depress breathing
• A high spinal anesthetic may paralyze the muscles of respiration
• An infant's stomach distension from facemask ventilation may splint the diaphragm and interfere with breathing
• Anaphylaxis management


  1. Stop administering causative agent

  2. Administer 100% oxygen

  3. Give IV saline bolus

  4. Administer adrenaline and consider steroids

  5. Give bronchodilators and antihistamine