Assessment Through Transcutaneous Brain Oximetry (NIRS) of Two Preoxygenation Techniques
Condition: Anesthesia; Functional
Study type: Interventional

Summary: 
      Preoxygenation techniques is currently considered a standard of care, but how they influence
      cerebral oxygenation remains largely unknown. In this study, the investigators compare three
      minutes tidal volume breathing versus eight vital capacity, deep breaths (8DB) technique.
      Forty-eight patients scheduled for surgery under general anesthesia were included in a
      randomized study design. The main endpoints were arterial partial pressure of O2 (PaO2) and
      regional cerebral oxygen saturation (rScO2 ; INVOS TM -5100- C) which were measured at
      baseline (T1), end of pre-oxygenation (T2) and after desaturation during apnoea to 95% (T3).
    

Detailed description: 
      Hypoxemia secondary to the inability to secure the airway remains the main cause of
      anesthesia-related morbidity and mortality. Preoxygenation with 100% oxygen before induction
      of anesthesia is currently considered a standard of care and practiced routinely for all
      patients, and especially carefully for high-risk cases. It is an essential component of the
      rapid sequence induction technique.

      Common pre-oxygenation techniques include the 3 min tidal volume breathing (3TV) and the
      eight vital capacity, deep breaths (8DB). Their efficiency has been extensively assessed by
      measuring the rate of decline of SaO2 during apnea after induction/paralysis, with 'time to
      desaturation (to 95% or 90%) being the endpoint of many studies. This is arguably a surrogate
      endpoint for oxygen stores and Pandit et al. estimated the total amount of oxygen taken up by
      the body in these techniques using breath-by-breath gas analysis. An even more relevant
      measure is the impact of preoxygenation on tissue stores of oxygen, but this is difficult to
      quantify. Especially, given its vulnerability to hypoxemia due to its high energy
      requirements compared to the low energy reserves, the brain is particularly susceptible.

      Cerebral oximetry is a noninvasive monitoring technique that uses near-infrared spectroscopy
      (NIRS) to measure regional cerebral oxygen saturation (rScO2). Continuous rScO2 monitoring
      has shown to be useful in detecting mismatch of oxygen supply and demand in the brain and
      assessing cerebral autoregulation in real-time. This offers a means to measure tissue
      oxygenation in a relevant organ with pre-oxygenation.

      The primary aim of the present study was to test the hypothesis that different
      pre-oxygenation techniques result in different degrees of cerebral oxygenation as measured by
      rScO2 with the INVOSTM-5100-C. The investigators wished to compare the 3TV method with the
      8DB method, as being the two methods that produced the highest increases in body oxygen
      stores in previous experiments; the null hypothesis that these would yield similar degrees of
      brain oxygenation. The investigators also wished to assess whether, regardless of the
      preoxygenation technique, there were differences between arterial PO2 and rScO2 dynamics with
      preoxygenation and subsequent apnoea.
    

Intervention name(s): Preoxygenation
Intervention type(s): Procedure
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Participant)
Primary purpose: Other
Keywords: airway management; general anaesthesia; standard of care; respiration; neurophysiological monitoring.