eMedicine Specialties > Clinical Procedures > Respiratory Management

Tracheal Intubation, Rapid Sequence Intubation

Keith A Lafferty, MD, Adjunct Assistant Professor of Emergency Medicine, Temple University; Consulting Staff, Department of Emergency Medicine, South West Regional Medical Center
Rick Kulkarni, MD, Medical Director, Assistant Professor of Surgery, Section of Emergency Medicine, Yale-New Haven Hospital

Updated: Oct 27, 2008

Introduction

Airway management is the most important skill for an emergency physician to master because failure to secure an adequate airway can quickly lead to death or disability.¹ Endotracheal intubation using rapid sequence intubation (RSI) is the cornerstone of emergency airway management.^2,3

The decision to intubate is sometimes difficult and requires clinical experience to recognize signs of impending respiratory failure. Patients who require intubation have at least one of the following 3 indications: 1) inability to maintain airway patency or protect the airway against aspiration, 2) ventilatory compromise or failure to adequately oxygenate pulmonary capillary blood, 3) anticipation of a deteriorating course that will eventually lead to the inability to maintain airway patency or protection, ventilate, or oxygenate.

RSI is the preferred method of endotracheal intubation in the emergency department (ED) because it results in rapid unconsciousness (induction) and neuromuscular blockade (paralysis). This is important in patients who have not fasted and are at much greater risk for vomiting and aspiration. To this end, the goal of RSI is to intubate the trachea without having to use bag-valve-mask (BVM) ventilation, which is often necessary when attempting to achieve intubating conditions with sedative agents alone (eg, midazolam, diazepam). Instead of titrating to effect, RSI involves administration of weight-based doses of an induction agent (eg, etomidate) immediately followed by a paralytic agent (eg, succinylcholine, rocuronium) to render the patient unconscious and paralyzed within 1 minute. This method has been proven safe and effective in EDs over the past 2 decades, and it is considered the standard of care.

RSI is not indicated in a patient who is unconscious and apneic. This situation is considered a "crash" airway and immediate BVM ventilation and endotracheal intubation without pretreatment, induction, or paralysis is indicated.

RSI should be approached with caution in a patient with a suspected difficult airway. If difficulty is anticipated, then an awake technique or the use of airway adjuncts (eg, fiberoptic intubation) is recommended.

Certain clinical scenarios call for pretreatment medications prior to induction/paralysis to optimize physiologic parameters for intubation, such as blunting the sympathetic response to laryngoscopy, preventing upward or downward spikes in blood pressure, avoiding increased intracranial pressure, and facilitating bronchodilation. These conditions include suspected high intracranial pressure (eg, intracranial hemorrhage or trauma), severe asthma or COPD, hypovolemic shock, aortic emergencies, and pediatric considerations among others.

Indications

• Failure to maintain airway patency
  • Swelling of upper airway as in anaphylaxis or infection
  • Facial or neck trauma with oropharyngeal bleeding or hematoma
  • Decreased consciousness and loss of airway reflexes
• Failure to protect airway against aspiration - Decreased consciousness that leads to regurgitation of vomit, secretions, or blood
• Failure to ventilate (ie, deliver air to the lungs/alveoli)
  • End result of failure to maintain and protect airway
  • Prolonged respiratory effort that results in fatigue or failure, as in status asthmaticus or severe COPD
• Failure to oxygenate (ie, transport oxygen to pulmonary capillary blood)
  • End result of failure to maintain and protect airway or failure to ventilate
  • Diffuse pulmonary edema
  • Acute respiratory distress syndrome (Click here to complete a Medscape CME activity on managing acute respiratory failure.)
  • Large pneumonia or air-space disease
• Anticipated clinical course or deterioration (eg, need for situation control, tests, procedures)
  • Uncooperative trauma patient with life-threatening injuries who needs painful procedure (eg, chest tube) or immediate CT scanning
  • Stab wound to neck with expanding hematoma
  • Septic shock with high minute-ventilation and poor peripheral perfusion
  • Intracranial hemorrhage with altered mental status and need for close blood pressure control

Contraindications

• Absolute
  • Total upper airway obstruction, which requires a surgical airway
  • Total loss of facial landmarks, which requires a surgical airway
• Relative
  • Anticipated "difficult" airway, in which endotracheal intubation may be unsuccessful, resulting in reliance on successful bag-valve-mask (BVM) ventilation to keep an unconscious patient alive (In this scenario, techniques for awake intubation and difficult airway adjuncts can be used.)
  • The "crash" airway, in which the patient is in an arrest situation, unconscious and apneic (In this scenario, no time is available for preoxygenation, pretreatment, or induction and paralysis. BVM ventilation, intubation, or both should be performed immediately without medications.)

Anesthesia

Rapid sequence intubation (RSI) is predicated on the administration of medications in a specific sequence. The 3 phases of medication administration are pretreatment, induction, and paralysis.

Preoxygenation

• Preoxygenation with high-flow oxygen via a nonrebreather mask for 5 minutes leading up to intubation results in supersaturation of oxygen in the tissues and displacement nitrogen (nitrogen washout). This allows the patient to maintain blood oxygen saturation during the apneic period of paralysis and allows the physician more time to successfully intubate. 
• In healthy adult volunteers who have been preoxygenated for 3-5 minutes, the average time to desaturation (oxygen saturation <90%) is approximately 8 minutes. This time is significantly shorter in patients who are critically ill and have a much higher metabolic demand for oxygen.¹

• Pretreatment agents are used to mitigate the physiologic response to laryngoscopy and induction and paralysis, which may be undesirable in certain clinical situations. 
• Pretreatment medications are typically administered 2 minutes prior to induction and paralysis. These medications can be remembered by using the mnemonic LOAD (ie, Lidocaine, Opioid analgesic, Atropine, Defasciculating agents).
  • Lidocaine (1.5 mg/kg IV) suppresses the cough or gag reflex experienced during laryngoscopy, which can result in increased intracranial pressure (ICP). For this reason, it is commonly administered to patients with suspected intracranial hemorrhage, tumor, or any other process that may result in increased ICP. No studies demonstrate the effectiveness of lidocaine for this indication in patients in the emergency department (ED). Lidocaine also has a theoretical benefit of bronchodilation and, therefore, has been advocated for patients with status asthmaticus and severe COPD who require intubation.
  • Opioid analgesic (fentanyl 3 mcg/kg IV) mitigates the physiologic increase in sympathetic tone associated with direct laryngoscopy (ie, blunts increases in blood pressure, heart rate, and mean arterial pressure). It has also been recommended in patients with suspected high ICP. It may also be useful in patients with an aortic emergency (eg, aortic dissection or leaking aortic aneurysm) in whom blood pressure spikes should be avoided.
  • Atropine (0.02 mg/kg IV) may decrease the incidence of bradydysrhythmia associated with direct laryngoscopy (stimulation of parasympathetic receptors in the laryngopharynx) and administration of succinylcholine (direct stimulation of cardiac muscarinic receptors). It is recommended as pretreatment for RSI in children younger than 10 years; however, it can also be used in adolescents and adults, if necessary (eg, symptomatic bradycardia).
  • Defasciculating agents reduce the duration and intensity of muscle fasciculations observed with the administration of succinylcholine (due to the stimulation of nicotinic acetylcholine receptors). The recommended dose is 10% of the paralyzing dose (eg, 0.01 mg/kg for vecuronium). Equivocal studies suggest such pretreatment may help reduce increases in intracranial pressure related to the procedure.

• Induction agents provide a rapid loss of consciousness that facilitates ease of intubation.
  • Etomidate (Amidate) (0.3 mg/kg IV) - Rapid onset, short duration, cerebroprotective, and not associated with significant drop in blood pressure; hemodynamically neutral compared with other agents, such as sodium thiopental. Most common agent used in the United States.
  • Midazolam (Versed) (0.3 mg/kg IV) - Slower onset (2-3 min without opioid pretreatment) and longer duration (up to several hours) than etomidate. A study by Sagarin et al from a national airway registry demonstrated that midazolam is usually underdosed when used for RSI, presumably because of the concern for hypotension.³ Note that the induction dose is about 20 mg for a 70 kg person. This medication has fallen out of favor in recent years because of its delayed time to induction, predilection for hypotension, and prolonged duration of action.
  • Sodium thiopental (Pentothal) (3-5 mg/kg IV) - Rapid onset, short duration, cerebroprotective, but associated with significant drop in blood pressure. Generally avoided in most patients since status of cardiovascular reserve is not known in the emergent setting.
  • Ketamine (Ketalar) (1-2 mg/kg IV) - "Dissociative" state, analgesic properties, bronchodilator, may increase intracranial pressure. Consider for patients with asthma or anaphylactic shock; avoid in other patients such as trauma patients at risk for head injury, patients with suspected or known aortic dissection or abdominal aortic aneurysm, and patients with acute myocardial infarction.

• Paralyzing agents provide neuromuscular blockade and are administered immediately after the induction agent.
• Neuromuscular blockade does not provide sedation, analgesia, or amnesia; thus, administering a potent induction agent is important.
  • Depolarizing neuromuscular blocker (eg, succinylcholine [Anectine] at 2 mg/kg IV or 4 mg/kg IM) - Rapid onset (45-60 sec) and shortest duration of action (8-10 min). Should be used with caution in patients with known or suspected hyperkalemia.
  • Nondepolarizing neuromuscular blocker (eg, rocuronium [Zemuron] at 1.0-1.2 mg/kg IV) - Slightly longer onset of action (60-75 sec) than succinylcholine and longer duration of action (30-60 min). Use with caution in patients in whom difficult intubation is possible. Does not result in muscle depolarization or defasciculation and does not exacerbate hyperkalemia.

Equipment

• Laryngoscope (confirm that light source is functional prior to intubation)
  
  

  

  Laryngoscope handle, No. 3 Macintosh (curved) blade, and No. 3 Miller (straight) blade.

  
  
• Endotracheal (ET) tube
• Stylet
• Syringe, 10 mL (to inflate ET tube balloon)
• Suction catheter (eg, Yankauer)
• Carbon dioxide detector (eg, Easycap)
• Oral and nasal airways
• Ambu bag and mask attached to oxygen source
• Assistant for cricoid pressure

Positioning

In cases of trauma in which cervical spine injury is suspected and not yet ruled out, intubation must be performed without movement of the head. Immobilization is best provided by an experienced assistant. In cases in which cervical injury is not a concern, proper head positioning greatly improves visualization.

• In the neutral position, the oral, pharyngeal, and laryngeal axes are not aligned to permit adequate visualization of the glottic opening.
  
  

  

  Proper alignment of the axes for tracheal intubation.

  
  
• Place the patient in the sniffing position for adequate visualization; flex the neck and extend the head. This position helps to align the axes and facilitates visualization of the glottic opening.

Technique

Preparation

• Confirm that intubation equipment is functional.
• Assess the patient for difficult airway (see Difficult Airway Assessment for recommended method). If the patient meets criteria for difficult airway, rapid sequence intubation (RSI) may be inappropriate. Awake laryngoscopy may be an alternative.
• Establish intravenous access.
• Draw up essential drugs and determine sequence of administration (induction agent immediately followed by paralytic agent).
• Review possible contraindications to medications.
• Attach necessary monitoring equipment.
• Check endotracheal (ET) tube cuff for leak.
• Tighten light bulb on laryngoscope blade. 

• Administer 100% oxygen via a non-rebreather mask for 3 minutes for nitrogen washout.
• If time is limited, instruct patient to take 8 vital capacity (as deep as possible) breaths of 100% oxygen.
• Assist ventilation with bag-valve-mask (BVM) system only if needed to obtain oxygen saturation >90%. This must be done with cricoid pressure.

• Administer drugs to mitigate the adverse effects associated with intubation.
• See Anesthesia for more information.

• Administer a rapidly-acting induction agent to produce loss of consciousness.
• Administer a neuromuscular blocking agent immediately after the induction agent.
• These medications should be administered as an intravenous push.

• Apply the Sellick maneuver (firm pressure over the cricoid cartilage) to prevent regurgitation of gastric contents.
  • Initiate this maneuver upon observing the beginning of unconsciousness.
  • Maintain pressure throughout intubation sequence until the position of the ET tube is verified.

Placement with proof

• Intubate the patient.
• Confirm tube placement.
  • Observe color change on a qualitative end-tidal carbon dioxide device.
  • Use the 5-point auscultation method: listen over each lateral lung field, the left axilla, and the left supraclavicular region for good breath sounds. No air movement should occur over the stomach.

• Tie the ET tube into place.
• Initiate mechanical ventilation.
• Obtain a chest radiograph.
  • Assess pulmonary status.
  • Confirm tube placement (do not use radiograph as primary method to confirm tube placement).
  • Ensure that mainstem intubation has not occurred.
• Administer appropriate analgesic and sedative agents for patient comfort.

Pearls

• To intubate a trauma patient with C-spine precautions, the cervical collar may be removed with a dedicated assistant providing inline immobilization.
• Position the head and neck into the sniffing position by flexing the neck and extending the atlanto-occipital joint. Reposition the head if an adequate view of the glottic opening is not achieved.
• The patient must be adequately preoxygenated to prevent desaturation during the period of apnea after the paralytic agent has been administered (to minimize the risk of gastric content aspiration). The least amount of ventilation support required to obtain good oxygen saturation should be used during this period. Blow-by high-flow oxygen via a nonrebreather mask is usually used, but for patients who are noted to desaturate (eg, beyond 90%), breaths delivered via 100% oxygen bag-valve-mask (BVM) may be required (however, use BVM only with cricoid pressure).
• To minimize the risk of gastric aspiration, the Sellick maneuver (firm pressure over the thyroid cartilage) may be initiated as soon as positive pressure ventilation is started (eg, during pretreatment if the patient is not able to maintain airway reflexes) and should be continued until inflation of the tracheal cuff of the endotracheal tube in the trachea.
• Firm backward, upward, and rightward pressure (BURP) on the patient's thyroid cartilage can improve the Cormack/Lehane view up to one full grade. Typically, the assistant performing the Sellick maneuver can assist, resulting in a combined Sellick-BURP maneuver.
• A No. 3 Macintosh or No. 3 Miller blade is generally sufficient for most patients, but a No. 4 blade (ie, next larger size) may be required in some adults.
• Provide appropriate analgesia and sedation for patient comfort after rapid sequence intubation (RSI) is successfully completed, especially if the patient is chemically paralyzed with a longer-acting paralytic agent (eg, vecuronium).
• RSI is a procedure performed for patients with a critical disease or traumatic process. The selection of technique and specific agents is determined individually for each patient and situation. This article focuses on straightforward RSI for adults. Different techniques, equipment, and agents may be used for complex or rescue situations.
• Accurate confirmation of correct placement of the tube in the trachea is essential.
  • Direct visualization of the tube was previously the criterion standard for confirming placement; however, this method can be fraught with human error.
  • The current criterion standard is end-tidal carbon dioxide detection, using either a calorimetric capnometer that changes color from purple to yellow with CO₂ exposure or a quantitative capnometer that measures CO₂ levels and can display a waveform. The yellow color change should occur rapidly within 1-2 breaths, and esophageal or supraglottic placement should be assumed if the color change is less rapid or does not occur at all. Color change may not be reliable in cases of prolonged cardiac arrest.
  • Clinical parameters such as pulse oximetry readings or tube condensation may be nonspecific and misleading. A canine study by Kelly and colleagues demonstrated tube condensation in up to 83% of esophageal intubations.⁴
• Cricoid pressure should be maintained until correct placement of the endotracheal tube is confirmed.
• The step of preoxygenation maximizes hemoglobin and plasma oxygen saturation and creates an oxygen reservoir in the lungs by replacing nitrogen at the alveolar level and supersaturating the blood with oxygen (nitrogen washout).
  • This oxygen reservoir in the lungs can eliminate the need for BVM ventilation for most patients undergoing RSI during the iatrogenically created period of apnea.
  • Preoxygenation is accomplished by delivering 100% oxygen at high flow given to a spontaneously breathing patient through a nonrebreather mask for 3 minutes without "bagging" the patient.
• Studies such as the one by Barker and colleagues have shown that 8 vital capacity breaths over 60 seconds results in the same degree of preoxygenation as the standard 3 minutes of tidal volume breathing of 100% oxygen by mask. This technique may be used as an alternate to the traditional 3-min tidal volume technique. Comorbidities such as the presence of a hypermetabolic state, obesity, or a primary respiratory problem (eg, CHF, ARDS, pneumonia) cause patients to desaturate rapidly despite attempts at adequate preoxygenation.
• A patient who is hypoxemic during attempts at intubation should undergo positive pressure ventilation with a BVM to raise PaO₂ levels. Cricoid pressure should be maintained to minimize airflow into the stomach.

Complications

• Right mainstem intubation
• Pneumothorax
• Dental trauma
• Post-intubation pneumonia
• Vocal cord avulsion
• Failure to intubate
• Hypotension
• Esophageal intubation
• Aspiration

Difficult Airway Assessment

Several methods exist to quickly assess the probability of success during tracheal intubation.¹ One tool for rapid assessment is the LEMON law, as described below. A patient in extremis may not be able to cooperate with all the sections of the LEMON assessment.

L: Look externally

Assessing the difficulty of an airway based on external physical features is not sensitive (not all patients who have a difficult airway appear to have a difficult airway prior to intubation) but is quite specific (most patients who appear to have a difficult airway do indeed have a difficult airway). Physical features such as a small mandible, large tongue, and short bull neck are all red flags for a difficult airway.

E: Evaluate the 3-3-2 rule

The chance for success is increased if the patient is able to insert 3 of his or her own fingers between the teeth, can accommodate 3 finger breadths between the hyoid bone and the mentum (see hyomental distance below), and is able to fit 2 finger breadths between the hyoid bone and the thyroid cartilage (see thyrohyoid distance below).

Hyomental distance (3 finger breadths).

Thyrohyoid distance (2 finger breadths).

Mallampati classification.

Multimedia

Media file 1: Proper alignment of the axes for tracheal intubation.

Media file 2: Hyomental distance (3 finger breadths).

Media file 3: Thyrohyoid distance (2 finger breadths).

Media file 4: Laryngoscope handle, No. 3 Macintosh (curved) blade, and No. 3 Miller (straight) blade.

Media file 5: Mallampati classification.

References

1. Reynolds SF, Heffner J. Airway management of the critically ill patient: Rapid-sequence intubation. Chest [serial online]. 2005; 127:1397-412. Available at http://www.chestjournal.org/cgi/content/full/127/4/1397.

2. Bair AE, Filbin MR, Kulkarni RG, et al. The failed intubation attempt in the emergency department: analysis of prevalence, rescue techniques, and personnel. J Emerg Med. Aug 2002;23(2):131-40. [Medline].

3. Sagarin MJ, Barton ED, Chng YM, et al. Airway management by US and Canadian emergency medicine residents: a multicenter analysis of more than 6,000 endotracheal intubation attempts. Ann Emerg Med. Oct 2005;46(4):328-36. [Medline].

4. Kelly JJ, Eynon CA, Kaplan JL, et al. Use of tube condensation as an indicator of endotracheal tube placement. Ann Emerg Med. May 1998;31(5):575-8. [Medline].

5. Walls RM. The decision to intubate. In: Walls RM, ed-in-chief; Murphy MF, Luten RC, Schneider RE, eds. Manual of Emergency Airway Management. 2^nd ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2004:1-7.

6. Walls RM. Rapid sequence intubation. In: Walls RM, ed-in-chief; Murphy MF, Luten RC, Schneider RE, eds. Manual of Emergency Airway Management. 2^nd ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2004:22-31.

Keywords

tracheal intubation, endotracheal intubation, oral intubation, tracheal intubation, orotracheal intubation, intubation, rapid sequence intubation, RSI, anesthesia and intubation, airway pharmacology, managing the acute airway, emergency airway management, emergency intubation, rapid tracheal intubation, difficult airway, paralysis, preoxygenation, induction, paralysis/induction

Contributor Information and Disclosures

Author

Keith A Lafferty, MD, Adjunct Assistant Professor of Emergency Medicine, Temple University; Consulting Staff, Department of Emergency Medicine, South West Regional Medical Center
Keith A Lafferty, MD is a member of the following medical societies: American Academy of Emergency Medicine, American Medical Association, and Pennsylvania Medical Society
Disclosure: Nothing to disclose.

Coauthor(s)

Rick Kulkarni, MD, Medical Director, Assistant Professor of Surgery, Section of Emergency Medicine, Yale-New Haven Hospital
Rick Kulkarni, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine
Disclosure: WebMD Salary Employment

Medical Editor

Michael R Filbin, MD, Clinical Instructor, Department of Emergency Medicine, Massachusetts General Hospital
Michael R Filbin, MD is a member of the following medical societies: American College of Emergency Physicians, Massachusetts Medical Society, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from broker recommendation; Avanir Pharma Stock Investment from broker recommendation

Managing Editor

Luis M Lovato, MD, Associate Clinical Professor, David Geffen School of Medicine at UCLA; Director of Critical Care, Department of Emergency Medicine, Olive View/UCLA Medical Center
Luis M Lovato, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Emergency Physicians, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

CME Editor

Gil Z Shlamovitz, MD, Assistant Professor of Emergency Medicine, University of Connecticut School of Medicine; Attending Physician, Emergency Department, Windham Community Memorial Hospital, Willimantic, CT; Attending Physician, Emergency Department, Hartford Hospital, Hartford, CT
Gil Z Shlamovitz, MD is a member of the following medical societies: American Academy of Emergency Medicine and American College of Emergency Physicians
Disclosure: Nothing to disclose.

Chief Editor

Jonathan Adler, MD, Attending Physician, Department of Emergency Medicine, Massachusetts General Hospital; Division of Emergency Medicine, Harvard Medical School
Jonathan Adler, MD is a member of the following medical societies: American Academy of Emergency Medicine and Society for Academic Emergency Medicine
Disclosure: eMedicine.com, Inc. Consulting fee Consulting

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