Optimal Anesthesia for Morbidly Obese Patients
Condition: Obesity; Anesthesia
MeSH terms: Obesity
Study type: Interventional
Phase: Phase 4

Summary: 
      Obese patients have a higher risk of anesthesia compared to the non-obese, including
      difficult intubation, rapid desaturation, difficult vascular access, and delayed recovery
      from anesthesia. This study aims to investigate the optimal anesthesia strategy for morbidly
      obese patients undergoing bariatric surgery in airway management, preoxygenation, arterial
      cannulation, and type of volatile anesthetic with M-Entropy guidance. The investigators will
      conduct a two-year clinical trial using permuted block randomization to evaluate multiple
      outcomes in patients undergoing laparoscopic sleeve gastrectomy (LSG) at Shuang Ho Hospital,
      Taipei Medical University. Particularly, the investigators will explore the role of
      ultrasound, an easily accessible modality for anesthesiologists, in examining upper airway
      anatomy and guiding arterial cannulation. The investigators will also assess the
      effectiveness of high-flow nasal cannula as a preoxygenation tool in preventing desaturation.
    

Detailed description: 
      The investigators will conduct a clinical trial using permuted block randomization and
      conforming to the CONSORT Statement to investigate multiple clinical outcomes in obese
      patients undergoing LSG at Shuang Ho Hospital, Taipei Medical University, New Taipei City,
      Taiwan. Three randomizations will be conducted, including radial artery catheterization using
      ultrasound guidance or blind palpitation, preoxygenation using HFNC or CPAP, and volatile
      anesthesia with desflurane or sevoflurane with or without M-Entropy guidance. A
      computer-generated list of randomizations (Research Randomizer, www.randomizer.org) will be
      used for these group allocations.

        1. Exploring potential risk factors of difficult intubation using ultrasound: A prospective
           single-blind cohort study

           Before surgery, all enrolled patients will be examined for appearance features regarding
           difficult airway, including interincisor distance (< 3 cm or not), mentohyoid distance,
           thyromental distance (< 6.5 cm or not), neck movement (< 80 degrees or not), neck
           circumference measured at the thyroid cartilage (> 43 cm or not), modified Mallampati
           score, upper lip bite test, and mandibular prognathism test. Besides, ultrasound will be
           used to assess upper airway anatomy, including pretracheal soft tissue depth27 and
           height and width of tongue base. Regarding pretracheal soft tissue depth, the distance
           from the skin to the anterior aspect of the trachea will be measured at three levels:
           vocal cords, thyroid isthmus, and suprasternal notch. The amount of soft tissue at each
           zone is calculated by averaging the amounts of soft tissue in millimeters obtained in
           the central axis of the neck and 15 millimeters to the left and right of the central
           axis.

           Moreover, the increased tongue volume and deposition of fat at the base of tongue in
           obese people has been shown to be highly associated with risk of obstructive sleep
           apnea. To measure the anatomy of tongue base, with the patient in a seated position, the
           convex transducer in the frequencies 1.5 to 5.0 MHz (GE C1-5-RS, GE Healthcare, Chicago,
           IL, USA) of a portable ultrasound device (LOGIQTM, GE Healthcare, Chicago, IL, USA) will
           be introduced to the skin of the neck in the submental region coronally, immediately
           cephalad to the body of the hyoid bone, and then in the area between the hyoid bone and
           the symphysis of the mandible. The patients will be instructed to avoid tongue
           movements, swallowing, or talking. Maximal width of tongue base, tongue base height, and
           maximal height of mid-tongue will be measured. The same anesthesiologist will perform
           all ultrasound measurements before surgery. Upon arrival at operating room, patients
           will be initially placed in a ramped position and then moved into a reverse
           Trendelenburg position to achieve a 30-degree incline of the thorax before
           preoxygenation.

           After induction of anesthesia, another anesthesiologist, blinded to all preoperative
           evaluation, will perform all laryngoscopies in this study. The laryngoscopy intubation
           will be performed using a size-3 or -4 Macintosh (Rüsch Inc., Duluth, GA, USA) blade and
           a styletted endotracheal tube. The laryngoscopic view will be graded according to
           Cormack and Lehane's classification with external laryngeal pressure applied.59
           Laryngoscopy views graded as III or IV are defined as difficult. In case of failed
           direct laryngoscopy despite external laryngeal manipulation in the first attempt,
           video-assisted laryngoscope GlideScope® (Verathon Medical, Bothell, WA, USA) will be
           used as an intubation rescue technique. The video-assisted laryngoscope will be kept on
           standby at the operating room before induction. The correct placement of the
           endotracheal tube will be confirmed by capnography.

        2. Radial artery catheterization using ultrasound guidance or blind palpation: An
           open-label randomized controlled trial

           Before surgery, the investigators will use a portable ultrasound device (LOGIQTM, GE
           Healthcare, Chicago, IL, USA) to measure the skin-to-artery distance of common sites of
           arterial cannulation of all enrolled patients, including radial artery, brachial artery
           and dorsalis pedis artery. Patients will be randomized in a ratio of 1:1 into ultrasound
           group (N=40) or palpation group (N=40). Radial artery cannulation will be performed
           using a radial artery catheterization kit (Arrow International Inc, Reading, PA, USA).
           For all patients, the wrist will be extended and taped to a board to maintain wrist
           extension, and the skin near the puncture site will be cleaned with chlorhexidine
           according to standard protocol. Allen test will be used to assess the vascular patency
           of the hand before cannulation of the radial artery. All patients will receive local
           skin anesthesia at the anticipated puncture site. All radial artery catheterizations
           will be performed by trained year 1 or 2 anesthesiology residents with similar levels of
           experience in both blind-palpation and ultrasound-guided radial arterial
           catheterization. All residents have performed at least 5 blind-palpation and 5
           ultrasound-guided radial arterial catheterizations prior to the study.

           In the ultrasound group, a linear vascular probe in the frequencies 5 to 13 MHz (GE
           12L-RS, GE Healthcare, Chicago, IL, USA) of portable ultrasound device (LOGIQTM, GE
           Healthcare, Chicago, IL, USA) will be applied to the skin to localize the radial artery
           and a 20-gauge catheter will be inserted distal to the transducer and directed according
           to the ultrasound image. Start time is defined as the time when the ultrasound probe is
           placed on the wrist. In the palpation group, the radial artery will be identified by
           palpation, and the cannula will be directed by continuous or intermittent palpation of
           arterial pulsation. The attending anesthesiologist will supervise the resident and act
           as the second operator if needed. An attempt is defined as a new penetration of the skin
           with the needle, followed by an unlimited number of subcutaneous needle redirections.
           Clinical judgment by the supervising anesthesiologist is used to determine the time
           allowed for an attempt, number of attempts allowed, and changes to a new site. The start
           time is defined when the operator's finger is initially placed on the patient's wrist.
           The end point for both methods is when the arterial catheter is successful placed.

        3. Comparing the effectiveness of preoxygenation between high-flow nasal cannula (HFNC) and
           facemask: A single-blind randomized controlled trial

           Patients will be randomized in an allocation ratio of 1:1 into HFNC group (N=40) or
           facemask group (N=40). Preoxygenation will be performed according to the randomization
           group for a 5-minute duration. In the HFNC group, preoxygenation will be performed using
           HFNC (Optiflow™, Fisher & Paykel Healthcare, Auckland, NZ), nasal prongs set at 30 L/min
           flow of heated and humidified 100% oxygen. In the facemask group, patients will breath
           spontaneously with an anesthetic facemask and 100% oxygen 15 L/min. Gas flow for HFNC or
           facemask can be adjusted depending on patients' tolerance. During laryngoscopy
           intubation, HFNC will be left in place with the nasal flow escalated to 50 L/min of 100%
           oxygen in order to achieve apneic oxygenation. In the facemask group, the facemask will
           be removed when apnea occurs. After tracheal intubation, correct placement of the
           endotracheal tube will be confirmed by capnography and the nasal prongs of the HFNC
           group will be removed. If desaturation (SpO2 < 92%) occurs, patients will be then
           administered 100% O2, and the recruitment maneuver (peak airway pressure 40 cm H2O for
           10 seconds) will be applied until SpO2 restores to baseline values.

        4. The effect of type of volatile anesthetics and M-Entropy guidance of anesthesia depth on
           postoperative recovery: A double-blind randomized controlled trial

      Patients will be randomized by a computer-generated list into one of the four groups,
      desflurane with usual care (N=20), desflurane with M-Entropy guidance (N=20), sevoflurane
      with usual care (N=20), and sevoflurane with M-Entropy guidance (N=20). At the operating
      room, a M-Entropy™ sensor and S/5™ module (GE Healthcare, Helsinki, Finland) will be applied
      to all patients' forehead before induction of anesthesia according to the manufacturer's
      recommendations. This will be connected to a M-Entropy Monitor that will be concealed from
      the patients and operators.

      In the M-Entropy group, dosage of volatile anesthetics will be adjusted to achieve the
      Response and State Entropy value between 40 and 60 from the start of anesthesia to the end of
      surgery. In the usual care group, dosage of volatile anesthetics will be titrated according
      to clinical judgment. This will be to maintain arterial pressure within 20% range of the
      baseline and the heart rate within the range 50 to 100 beats/min. In case of signs of
      inadequate anesthesia (e.g. movement, cough and swallowing), anesthetic dose will be
      increased. M-Entropy monitoring will be continued in the usual care group, but the Entropy
      number and EEG waveform will be concealed from the anesthetist in charge. Entropy values,
      hemodynamic, and expiratory gas data will be recorded in 5-min intervals. In all patients,
      cessation of general anesthesia will be timed to facilitate early awakening after wound
      closure. All patients will be decurarized from rocuronium-induced neuromuscular blockade with
      sugammadex dosed at 2 mg/kg ideal body weight + 40%.
    

Intervention name(s): Exploring potential risk factors of difficult intubation using ultrasound; Radial artery catheterization using ultrasound guidance or blind palpation; Comparing the effectiveness of preoxygenation between high-flow nasal cannula and facemask; Type of volatile anesthetics and M-Entropy guidance of anesthesia depth
Intervention type(s): Procedure; Procedure; Device; Drug
Intervention description(s): Before surgery, ultrasound will be used to assess pretracheal soft tissue depth and height and width of tongue base. The distance from the skin to the anterior aspect of the trachea will be measured at three levels: vocal cords, thyroid isthmus, and suprasternal notch. With the patient in a seated position, the convex transducer of a portable ultrasound device (LOGIQTM, GE Healthcare, Chicago, IL, USA) will be introduced to the skin of the neck in the submental region coronally, immediately cephalad to the body of the hyoid bone, and then in the area between the hyoid bone and the symphysis of the mandible. Maximal width of tongue base, tongue base height, and maximal height of mid-tongue will be measured. The laryngoscopy intubation will be performed using a size-3 or -4 Macintosh (Rüsch Inc., Duluth, GA, USA) blade and a styletted endotracheal tube. The laryngoscopic view will be graded according to Cormack and Lehane's classification with external laryngeal pressure applied.; For all patients, the wrist will be extended and taped to a board to maintain wrist extension. All patients will receive local skin anesthesia at the anticipated puncture site. All radial artery catheterizations will be performed by anesthesiology residents with similar levels of experience in both blind-palpation and ultrasound-guided radial arterial catheterization. In the ultrasound group, a linear vascular probe of portable ultrasound device (LOGIQTM, GE Healthcare, Chicago, IL, USA) will be applied to the skin to localize the radial artery and a 20-gauge catheter will be inserted distal to the transducer and directed according to the ultrasound image. In the palpation group, the radial artery will be identified by palpation, and the cannula will be directed by continuous or intermittent palpation of arterial pulsation. An attempt is defined as a new penetration of the skin with the needle, followed by an unlimited number of subcutaneous needle redirections.; In the HFNC group, preoxygenation will be performed using HFNC (Optiflow™, Fisher & Paykel Healthcare, Auckland, NZ), nasal prongs set at 30 L/min flow of heated and humidified 100% oxygen. In the facemask group, patients will breath spontaneously with an anesthetic facemask and 100% oxygen 15 L/min. Gas flow for HFNC or facemask can be adjusted depending on patients' tolerance. During laryngoscopy intubation, HFNC will be left in place with the nasal flow escalated to 50 L/min of 100% oxygen in order to achieve apneic oxygenation. In the facemask group, the facemask will be removed when apnea occurs. After tracheal intubation, correct placement of the endotracheal tube will be confirmed by capnography and the nasal prongs of the HFNC group will be removed.; At the operating room, a M-Entropy™ sensor and S/5™ module (GE Healthcare, Helsinki, Finland) will be applied to all patients' forehead before induction of anesthesia according to the manufacturer's recommendations. Patients will be randomized to Sevoflurane or Desflurane as the single volatile anesthetics for general anesthesia.
Besides, patients will be randomized to M-Entropy group or controls. In the M-Entropy group, dosage of volatile anesthetics will be adjusted to achieve the Response and State Entropy value between 40 and 60 from the start of anesthesia to the end of surgery. In the usual care group, dosage of volatile anesthetics will be titrated according to clinical judgment. M-Entropy monitoring will be continued in the usual care group, but the Entropy number and EEG waveform will be concealed from the anesthetist in charge.
Intervention MeSH terms: Anesthetics
Allocation: Randomized
Intervention model: Factorial Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment
Keywords: Obesity; Anesthesia; Enhanced recovery after surgery; Difficult intubation; Preoxygenation; Depth of anesthesia; High-flow nasal cannula