Comparison of the Effects of High, Low and Minimal Flow Anesthesia Managements on ORI and Partial Oxygen Pressure
Condition: General Anesthetic
Study type: Observational [Patient Registry]

Summary: 
      The aim of our study is to show that continuous oxygen reserve index monitoring is a
      non-invasive monitoring method that can be used as a supporting parameter to PaO2 in blood
      gas in hypoxia and hyperoxia monitoring when different fresh gas flow is used in general
      anesthesia.
    

Detailed description: 
      Ninety patients included in the study were classified into three groups. After the high flow
      period, FGF and inspired oxygen fraction (FiO2) was set to be 4 L/m and 40% in group H (high
      flow), 1 L/m and 50% in group L (low flow) and 0.5 L/m and 68% in group M (minimal flow),
      respectively.

      Patients were transferred into the operating room, monitored and premedication with 0.03
      mg/kg of midazolam was administered. Subsequently, the right radial artery was cannulated
      under local anesthesia and basal blood samples were taken. After preoxygenation (100% O2, 6
      L/min, 3 min.), anesthesia induction was performed with intravenous administration of 40-60
      mg lidocaine, 2 mg/kg propofol, 0.6 mg/kg rocuronium and 1.5 mcg/kg fentanyl. Patients were
      ventilated in volume-controlled mode (Dräger Perseus® A500 Anaesthesia Workstation, Dräger,
      Germany) that allows continuous monitorization of airway pressure, exhaled gas volume, FiO2,
      volatile anesthetic substance concentration, and CO2 concentration within the scope of the
      Common European Standard EN 740. Medical air was used as the carrier gas. End-tidal carbon
      dioxide (EtCO2) was continuously monitored after intubation, and tidal volume and ventilation
      rates were adjusted to maintain EtCO2 at 30-40 mmHg. In maintenance, general anesthesia was
      provided in all three groups by inhalation of remifentanil 0.05-0.2 mcg/kg/min and FGF 4
      L/min 50% oxygen-medical air mixture with 6-8% desflurane. After intubation, 6% desflurane
      was administered with a fresh gas flow of 4 L/min for 10 minutes in all three groups, and the
      MAC value was adjusted to 1.

      Thereafter, oxygen 1 L/min, and medical air 3 L/min (FGF 4 L/min, FiO2 40%) were administered
      to patients in group H for high-flow anesthesia; oxygen 0.37 L/min, medical air 0.63 L/min
      (FGF 1 L/min, FiO2 50%) to patients in group L for low-flow anesthesia; oxygen 0.3 L/min and
      medical air 0.2 L/min (FGF 0.5 L/min, FiO2 68%) to patients in group M under minimal flow
      anesthesia. After reaching adequate MAC values after 10 minutes of intubation, FiO2 was
      reduced to 40% in Group H, keeping the FGF unchanged; in Group L fresh gas flow was reduced
      to 1 L/min, in Group M fresh gas flow was reduced to 0.5 L/min, and the scale setting of
      desflurane was adjusted in order to achieve MAC 1 for the remainder of the surgery.

      A disposable sensor (RD Rainbow Lite Set ORI Probe, Masimo Corp. Irvine CA), shielded from
      light, was placed on the left index finger to record the data displayed with Masimo Radical 7
      pulse CO-Oximeter (Masimo Corp. Irvine CA).

      At the end of the surgical procedure in all patients, the vaporizer was turned off and high
      FGF (4 L/min, FiO2 100%) was applied to ensure rapid removal of the anesthetic gases from the
      lungs, and manual ventilation was started. Sugammadex (2-4 mg/kg iv.) was administered to
      reverse the residual muscle relaxation at the end of the operation in patients who did not
      experience complications during the operation, and after spontaneous breathing was achieved,
      the patients were extubated in the operating room.
    

Intervention name(s): Masimo Radical-7 Pulse CO-Oximeter
Intervention type(s): Device
Intervention description(s): The Masimo Radical-7 Pulse CO-Oximeter is a device for the measurement of pulse oximetry, oxygen reserve index (ORi), perfusion index (PI), and pleth variability index (PVI). The device is the product of a company called Masimo Inc, Irvine, CA, USA
Observational model: Cohort
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        ASA II and III patients aged between 18-75 years, who were scheduled to undergo elective
        open abdominal surgery lasting <60 minutes under general anesthesia
      
Keywords: low flow anesthesia; oxygen reserve index; arterial oxygen pressure