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Endotracheal Intubation by Direct Laryngoscopy

Rendell W. Ashton, MD

Christopher M. Burkle, MD


  • Inability to oxygenate patient
    • (SpO2 < 90%, PaO2 < 55)
  • Inability to ventilate patient
    • (rising PaCO2, respiratory acidosis, mental status change or other symptoms)
  • Patient unable to protect the airway


  • Neck immobility or increased risk of neck trauma (e.g. rheumatoid arthritis, cervical spine injury, etc.)-consider fiberoptic intubation
  • Inability to open mouth (e.g. trismus, scleroderma, surgical wiring, etc.)-consider nasal intubation, either blind or fiberoptic, or surgical airway


NOTE: check beforehand to make sure everything works

  • Patient positioning equipment
    • Bed or procedure table that can be raised and lowered
    • Pillows or blankets that can be rolled and placed under patient for optimal positioning (discussed below)
  • Monitoring equipment
    • Pulse oximeter
    • Blood pressure gauge
    • Cardiac monitor
  • Oxygenation equipment
    • Oxygen source and tubing
    • Face mask
    • Anesthesia bag or self-inflating ambu-bag
    • Suction catheter with Yankauer tip
  • Premedication and induction equipment
    • Intravenous access
    • Premedication agents (discussed below)
    • Induction agents (discussed below)
    • Paralytic agents (discussed below)
  • Intubation equipment
    • Laryngoscope handle and blades of different sizes and shapes (remember to check light bulb on each blade):
      • Curved blades (e.g. Macintosh blades)
      • Straight blades (e.g. Miller or Wisconsin blades)
    • Endotracheal tubes
      • Have several different sizes available
      • Remember to check cuff for leaks
    • Means of securing tube in place
      • Commercial products specifically designed for this purpose are recommended
      • Alternatives include tape or ties
  • Equipment for verifying tube position after placement
    • Stethoscope
    • Carbon dioxide detector or end-tidal CO2 monitor
    • Esophageal syringe or bulb syringe
    • Chest x-ray to verify position is also required

      Click image to enlarge.

      cxr1 cxr2

Preparation and Anesthesia ( See rapid sequence timeline)

  • Assemble equipment
  • Calculate doses and draw medications into syringes
  • Check IV access and flush fluid
  • Do you predict a difficult airway?
  • Is the patient unresponsive or near death?
  • Position patient
    • Bed at comfortable height for laryngoscopist
    • Patient aligned without lateral deviation of head or neck
    • Shoulders and/or neck supported with rolls or pillows to allow positioning of head
    • Neck flexed approx. 15 degrees on chest
    • Head hyperextended on neck to maximum comfortable degree (may be best done after induction)
  • Preoxygenate patient 5 minutes on 100% oxygen via mask (straps or person holding in place)
  • Consider premedications, optional for most patients-usually given 2-3 minutes prior to induction
    • Defasciculating drug (for patients who will get succinylcholine, but may not tolerate fasciculation, e.g. elevated intracranial or intraocular pressure)
      • Succinylcholine 0.15 mg/kg (10% of paralyzing dose)
      • Vecuronium 0.01 mg/kg (10% of paralyzing dose)
    • Prevention of vagal response (especially children younger than age 5 often have bradycardic response to laryngoscopy)
      • Atropine 0.02 mg/kg
    • Prevention of worsening intracranial pressure or bronchospasm
      • Lidocaine 1.5 mg/kg
    • Prevention of hypertensive response in patients with elevated intracranial pressure, heart disease or aneurysm
      • Fentanyl 3 mcg/kg
  • Administer a precalculated dose of an induction agent:
    Dose Advantages Cautions


    0.3 mg/kg

    Good for low blood pressure; okay in hypovolemia

    Nausea and vomiting on emergence


    1.5 mg/kg

    Good for low blood pressure, hypovolemia; good in asthma

    Caution in elevated intracranial pressure or heart disease


    2 - 2.5 mg/kg

    Rapid onset and recovery

    Caution if hypovolemic or risk of hypotension


    3 - 5 mg/kg

    Multiple drug interactions; caution if hypovolemic or risk of hypotension

  • Administer a precalculated dose of a paralytic agent
    Dose Characteristics Cautions


    1 - 1.5 mg/kg

    Rapid onset, rapid recovery; fasciculation

    Contraindicated in hyperkalemia, crush injury, renal failure, extensive burns, elevated intracranial or intraocular pressure


    0.6 - 1.2 mg/kg

    No fasciculation

    Longer acting-may be problematic if intubation attempt fails


    0.08 - 0.1 mg/kg


    0.4 - 0.5 mg/kg


Laryngoscopy technique

  • Check to verify effect of induction and paralytic agent
  • Optimize patient position, if needed
  • With suction available at hand, hold laryngoscope in left hand and endotracheal tube in right hand
  • Open the patient's mouth with a right-handed scissor technique
  • Insert the laryngoscope blade on the right side of the mouth and use it to sweep the tongue to the left
  • Advance the blade until landmarks are recognized-usually the tip of the epiglottis or the arytenoid cartilages
  • Lift (not lever) the laryngoscope in the direction of the handle to lift the tongue and posterial pharyngeal structures out of the line of sight, bringing the glottis into view (Mac or Miller Technique)
    Miller Blade Visualization
    Mac Blade Visualization
  • When the vocal cords or the arytenoid cartilages are clearly seen, advance the tube down the right side of the mouth, keeping the vocal cords in view until the last possible moment, then advance the tube through the vocal cords (Mac or Miller Technique).
    Mac Blade Intubation
    Miller Blade Intubation
  • Insert the tube to 23 cm (at incisors) in men and 21 cm in women, then inflate the cuff
  • Attach bag ventilator to tube and verify tube position immediately
    • Listen for breath sounds over epigastrium (one breath), then to each hemithorax in the midaxillary line (one breath on each side)
    • Attach CO2 detector to tube or use end-tidal CO2 monitor to verify return of carbon dioxide with each breath
    • Use esophageal syringe or bulb syringe to verify tube is in noncollapsing trachea (caution- this technique may be falsely negative if tube is in esophagus and stomach is full of air)
  • Secure tube in position and request chest x-ray to confirm position.
  • Ensure proper attachment to mechanical ventilator and review ventilator settings.
  • Consider ongoing sedation, particularly if induction agent may wear off before paralytic agent.


  • Can't intubate, but can ventilate with mask -- continue mask ventilation until more experienced laryngoscopist arrives, defer intubation or consider alternative technique, such as fiberoptic intubation.
  • Can't intubate, can't ventilate -- see " failed airway" algorithm.
  • Aspiration-avoidable if Sellick maneuver done properly and maintained throughout procedure.
  • Trauma from laryngoscope
    • Teeth-avoidable with proper laryngoscopy technique.
    • Soft tissues (bleeding)-usually avoidable with proper laryngoscopy technique.
    • Edema-usually due to repeated attempts at laryngoscopy; key is to optimize something with each new attempt, not simply repeat procedure without addressing a possible reason for failure.
  • Equipment failure-have backup equipment nearby and verify that everything works beforehand.

Quiz Questions

  1. Which of the following techniques is most reliable to insure that the endotracheal tube has been properly placed?
  2. Preoxygenation prior to rapid sequence induction is considered adequate when:
  3. The larygoscope blade is used to:
  4. As compared to a straight blade, a curved blade may:

Prepared by:
Rendell W. Ashton, MD
Mayo Clinic, Rochester, MN May 2004
Reviewed by:
Christopher M. Burkle, MD
Mayo Clinic, Rochester, MN May 2004


  1. Hagberg, CA. Handbook of Difficult Airway Management. Churchill Livingstone. New York. 2000.
  2. Benumof, JL. Airway Management Principles and Practice. Mosby. St Louis. 1996