هايبوكسيا

• ريذختلا ةدام يرظنلا


  Hypoxia During Anesthesia

  
• Anesthesia providers make every effort to avoid hypoxemia because of the risk of irreversible damage to the myocardium, brain, and other organs. Despite these efforts, hypoxemia continues to occur in the operating room at a high rate.

  
• Hypoxemia is one of the patients' most serious risks during anesthesia and surgical care. Pulse oximetry has become an essential component of operating room technology to detect, treat, and reduce the degree of intraoperative hypoxemia in the world.

  
• 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

  • AIRWAY
  • BREATHING
  • CIRCULATION
  • DRUGS
  • EQUIPMENT
• AIRWAY


  1. An obstructed airway prevents oxygen from reaching the lungs

  2. The tracheal tube can be misplaced e.g. in the esophagus

  3. Aspirated vomit can block the airway
• BREATHING


  1. Inadequate breathing prevents enough oxygen from reaching the alveoli

  2. Severe bronchospasm may not allow enough oxygen to reach the lungs nor carbon dioxide to be removed from the lungs

  3. A pneumothorax may cause the affected lung to collapse

  4. High spinal anesthesia may cause inadequate breathing
• CIRCULATION


  1. Circulatory failure prevents oxygen from being transported to the tissues

  2. Common causes include hypovolemia, abnormal heart rhythm, or cardiac failure
• DRUGS


  1. Deep anesthesia may depress breathing and circulation

  2. Many anesthetic drugs cause a drop in blood pressure

  3. Muscle relaxants paralyze the muscles of respiration

  4. Anaphylaxis can cause bronchospasm and low cardiac output
• EQUIPMENT


  1. Problems with the anesthetic equipment include disconnection or obstruction of the breathing circuit

  2. Problems with the oxygen supply include an empty cylinder

  3. Problems with the monitoring equipment include battery failure in the oximeter or a faulty probe
• Management of Hypoxia


  1. Check if the airway is clear

  2. Check if the patient is breathing adequately

  3. Check if the circulation is normal

  4. Check for drug effects

  5. Check if the equipment is working properly

  
• Laryngospasm


  Mild laryngospasm - high pitched inspiratory noise; Severe laryngospasm - silent, no gas passes between the vocal cords
• Unrecognized inadvertent oesophageal 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.
• Normally inadequate circulation is revealed by the pulse oximeter as a loss or reduction of pulsatile waveform or difficulty getting a pulse signal.
• Management of Anaphylaxis


  1. Stop administering the causative agent

  2. Administer 100% oxygen

  3. Give intravenous saline starting with a bolus of 10ml/kg

  4. Administer adrenaline and consider giving steroids

  5. Bronchodilators and an antihistamine