The Role of Perioperative Ventilation (Gas Exchange) During Intrabdominal Surgery on Cognitive Function
Condition: Response to Hyperoxia; Hypocapnia
MeSH terms: Hyperoxia; Hypocapnia
Study type: Interventional

Summary: 
      Abdominal surgery commonly requires perioperative relaxation and therefore controlled
      mechanical ventilation. However, respiratory support can be associated with minor, yet
      clinically significant changes in blood gas content. The inadvertent hyperoxia (excessively
      high oxygen) and/or hypocapnia (excessively low carbon dioxide) can result in transient
      changes in cerebral blood flow and cognitive impair.
    

Detailed description: 
      The moderate hyperventilation resulting in hypocapnia as well as hyperoxia are common
      features of mechanical ventilation during general anesthesia. While mild hyperventilation is
      routinely advocated in laparoscopic surgical interventions, increased FiO2 is set to
      reinforce safety of respiratory support. Hypocapnia may cause disturbances of cerebral blood
      flow due to narrowing of cerebral vessels and a decrease cerebral blood flow. Hypocapnia is
      particularly injurious to the brain in premature infants. Factors that may predispose the
      immature brain to such injury include poorly developed vascular supply to vulnerable areas,
      antioxidant depletion by excitatory amino acids, and the lipopolysaccharide and cytokine
      effects that potentiate destruction of white matter. Data from neonates clearly suggest that
      severe hypocapnia after hyperventilation contribute to adverse neurologic outcomes. The use
      of high concentrations of oxygen can lead to a number of events such as the formation of
      harmful free radicals and activation of lipid peroxidation, resulting in secondary brain
      injury due to hyperoxia, particularly after suffering anoxia of the brain in resuscitated
      victims of sudden cardiac arrest. It is recommended to use the fraction of oxygen to maintain
      saturation at the level of 94-98% when performing cardiopulmonary resuscitation (CPR), due to
      the risk of reperfusion injury. These disturbances of gas exchange, yet transient can
      interfere in cerebral blood flow and therefore mental functions.

      The primary aim of this study was the assessment of the impact of intraoperative gas exchange
      (hypocapnia, hyperoxia and their combinations) on the state of higher nervous activity
    

Intervention name(s): mechanical ventilation
Intervention type(s): Procedure
Intervention description(s): Patients subjected to scheduled laparoscopic cholecystectomy were enrolled to the ongoing prospective study and randomized into four groups: 1) normoxia and normocapnia (nO2-nCO2), 2) hyperoxia and normocapnia (hO2-nCO2), 3) normoxia and hypocapnia (nO2-lCO2), and 4) hyperoxia-hypocapnia (hO2-lCO2).
Normoxia PaO2 was referred to PaO2 of 70-140 mm Hg, hyperoxia 150-300 mm Hg, normocapnia PaCO2 of 35-48 mmHg and hypocapnia PaCO2 of 25-35 mmHg.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Prevention
Keywords: cognitive dysfunction; mechanical ventilation; hyperoxia; hypocapnia