Early Warning for Desaturation by Oxygen Reserve Index
Condition: Desaturation of Blood; Anesthesia
Study type: Observational [Patient Registry]

Summary: 
      During the induction of general anesthesia, the anesthesiologist needs to provide the oxygen
      supply to meet the patient's needs continuously. In the clinical scenario, the pulse oximeter
      is used as a standard to monitor hemoglobin oxygen saturation (SpO2) but is limited to assess
      the oxygenation status beyond the measurement of 100%. The Oxygen Reserve Index (ORi) is a
      dimensionless parameter between 0 and 1 that is related to real-time oxygenation reserve
      status. This study was designed to evaluate the duration of warning time for desaturation
      provided by different ORi alarm triggers during prolonged apnea in surgical patients. The
      primary endpoint was the duration of additional warning time provided by the ORi trigger. The
      secondary endpoint was the correlation of ORi and PaO2.
    

Detailed description: 
      This is an observational study of the routine clinical practice with no specific additional
      interventions required.

      The investigators enrolled the American Society of Anesthesiologists (ASA) physical status I
      to III patients scheduled for elective surgery with planned arterial catheter placement
      before induction. Patients were positioned supine on the operating room table. Standard
      monitors and the ORi sensor were placed. The patients were preoxygenated with a facemask
      (flow rate of 8 to 10 liters/minute) for 3 minutes with spontaneous ventilation. Propofol
      (2-2.5 mg/kg), fentanyl (2-3 mcg/kg) and rocuronium (0.6-0.9 mg/kg) were administrated to
      achieve anesthesia induction during following 3 minutes. The patient was keeping ventilated
      manually by the anesthesiologist during the induction phase and intubated under direct
      visualization with a video-assisted laryngoscope at 6 minutes. The endotracheal tube was not
      connected to the breathing circuit to avoid apneic oxygenation. The patients remained apneic.
      Ventilation was resumed when SpO2 fell to 90%. ORi and SpO2 were recorded every ten seconds.
      Arterial blood is sampled every minute, from preoxygenation to resumed ventilation, to
      observe blood oxygen concentration changes.
    

Intervention name(s): Oxygen reserve index
Intervention type(s): Device
Intervention description(s): This is an observational study of the routine clinical practice with no specific additional interventions required. The investigators enrolled the ASA physical status I to III patients scheduled for elective surgery with planned arterial catheter placement before induction. ORi and standard monitors were placed. The patients were preoxygenated and received anesthesia induction as routine clinical practice. Intubation was done by video-laryngoscope. The endotracheal tube was not connected to the breathing circuit to avoid apneic oxygenation. Ventilation was resumed when SpO2 fell to 90%. ORi and SpO2 were recorded every ten seconds.
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Male and female patients aged 18 to 80 years with ASA physical status I to III scheduled
        for elective surgery with planned arterial catheter placement before induction of general
        anesthesia and did not match the exclusion criteria.
      
Keywords: Oxygen reserve index; Induction of general anesthesia