Rapid Intubation Sequence: Indications, Contraindications, Equipment, Anesthesia, Positioning, Complications and Preparation

Airway management may be one of the most important skills for an emergency physician to master.

Failure to ensure an adequate airway can quickly lead to death or disability.

Endotracheal intubation with rapid sequence intubation (RSI) is the cornerstone of emergency airway management.

The decision to intubate is sometimes difficult. Clinical experience is required to recognize the signs of impending respiratory failure .

Patients requiring intubation have at least one of the following five indications:

  • Inability to maintain airway patency.
  • Inability to protect the respiratory tract against aspiration.
  • Do not ventilate.
  • Lack of oxygen.
  • Anticipation of a course of deterioration that will eventually lead to respiratory failure.

RSI is the preferred method of endotracheal tube intubation (ETTI) in the emergency department (ED). This is because it produces rapid unconsciousness (induction) and neuromuscular blockage (paralysis).

This is important in patients who have not fasted and because of this they are at a much higher risk of 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 intubation conditions with only sedative agents.

Rather than titration to effect, RSI involves the administration of doses based on the weight of an induction agent (eg, ketamine, etomidate ).

This is immediately followed by a paralyzing agent (eg, rocuronium, succinylcholine) to render the patient unconscious and paralyzed within one minute.

These drugs share common characteristics in short onset / compensation times and powerful efficacies.

This method has been shown to be safe and effective in EDs over the past 4 decades, and is considered the standard of care.

The use of neuromuscular blocking agents in patients undergoing emergent tracheal intubation is associated with a significant decrease in complications related to the procedure.

But this only when administered by experienced and well-trained emergency room physicians.

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

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

Alternatively, anesthesia personnel can be called in to help secure the airway of a difficult-to-intubate patient.

Extrapolating known techniques and procedures that are intuitive and evidence-based from the emergency department to the field often makes clinical sense.

However, the same standards that govern such modalities must apply wherever they are practiced. Recent literature has questioned the benefit of RSI in the prehospital setting.

Contributing factors may be the induction of hyperventilation and hypoxia , which have been shown to increase mortality in trauma patients undergoing prehospital RSI.

Additional studies have shown that the use of prehospital RSI is associated with a higher incidence of transient and prolonged hypoxia (57% of patients with a mean hypoxia time of 60 s). This situation is often unnoticed by the paramedic.

The lack of initial and ongoing training, national variability in paramedical protocols, and inadequate experience must be studied and monitored.

Randomized prospective studies are needed to better delineate and define the use of prehospital IHR.

The ubiquitous use of video-assisted laryngoscopes (VALs) in EDs has been shown to reduce complications in RSI.

As more prehospital personnel are trained in this modality, similar results may be shown.

In fact, the amount of training required in VAL compared to direct laryngoscopy is less and glottic visualization has been shown to be easier.

There is a general lack of clinical evidence in several areas of RSI, including the following:

  • The use of atropine as an adjunctive agent for children.
  • The role of lidocaine in pretreatment.
  • The role of a “defasciculating” or priming of a non-depolarizing paralyzing agent.
  • Relative contraindications to the use of succinylcholine.
  • The amount and methods of preoxygenation.
  • The need to use cricoid pressure (Sellick’s maneuver).

The use of the Sellick maneuver to prevent aspiration has never been demonstrated, but has been confirmed in increased airway resistance and decreased tidal volumes.

Also, MRI studies have shown that the esophagus is more to the right of the trachea than it is to the back.

Indications

  • Failure to maintain the tone of the airways.
  • Swelling of the upper respiratory tract as in anaphylaxis or infection.
  • Facial or neck trauma with oropharyngeal hemorrhage or hematoma.
  • Decreased consciousness and loss of airway reflexes.
  • Lack of protection of the respiratory tract against aspiration.
  • Decreased consciousness leading to regurgitation of vomit, secretions, or blood.
  • Do not ventilate.
  • End result of failure to maintain and protect the airways.
  • Prolonged respiratory effort resulting in fatigue or failure, as in severe asthma or COPD.
  • Not oxygenate (that is, carry oxygen to the pulmonary capillary blood).
  • End result of lack of maintenance and protection of the respiratory tract or lack of ventilation.
  • Diffuse pulmonary edema .
  • The acute respiratory distress syndrome.
  • Large pneumonia or airspace disease.
  • Pulmonary embolism
  • Cyanide toxicity, carbon monoxide toxicity, methemoglobinemia.
  • Anticipated clinical course or deterioration (eg, Need for situational control, tests, procedures).
  • Uncooperative trauma patient with life-threatening injuries requiring procedures (eg, chest tube) or immediate CT scan.
  • Stab in the neck with expanding hematoma.
  • Septic shock with high ventilation and poor peripheral perfusion.
  • Intracranial hemorrhage with altered mental status and need for strict control of blood pressure.
  • Cervical spine fracture with concern for edema and loss of airway patency.

Contraindications

Absolute

  • Total upper airway obstruction, requiring a surgical airway.
  • Total loss of facial / oropharyngeal landmarks, requiring a surgical airway.

Relative

The anticipated “difficult” airway, in which endotracheal intubation may be unsuccessful, resulting in dependence on successful valve bag ventilation to keep the unconscious patient alive.

In this setting, techniques for awake intubation and difficult airway adjuncts can be used.

Multiple methods can be used to assess the airway and risk of difficult intubation (eg, LEMON Rule, 3-3-2, Mallampati class, McCormack and Lehane grade).

The “shock” airway is one in which the patient is arrested, unconscious, and apneic.

In this scenario, the patient is already unconscious and may be flaccid, in addition, there is no time available for preoxygenation, pretreatment or induction and paralysis.

Team

The kit includes the following:

  • Laryngoscope.
  • Laryngoscope handle, No. 3 Macintosh (curved) blad.
  • Laryngoscope handle, n. Macintosh sheet 3 (curved) and No. 3 Miller blade (straight).
  • Endotracheal tube (ET).
  • Stylet.
  • Syringe, 10 ml (to inflate the balloon with ET tube).
  • Suction catheter (eg, Yankauer).
  • Carbon dioxide detector (eg Easycap).
  • Oral and nasal airways.
  • Ambu bag and mask attached to oxygen source.
  • Nasal cannula.

It is important to confirm that the light source is functional before intubation.

A 2010 study demonstrated that single-use metal laryngoscope blades resulted in a lower failed intubation rate than reusable metal blades.

Anesthesia

Rapid sequence intubation (RSI) is based on the administration of medications in a specific sequence.

The two phases of drug administration are induction and paralysis. In general, preoxygenation takes place while medications are being prepared.

Preoxigenación

Pre-oxygenation is performed with high-flow oxygen through a non-breathable mask for 3-5 minutes prior to intubation.

This results in oxygen supersaturation in the alveoli through nitrogen displacement (nitrogen washout).

This allows the patient to maintain the oxygen saturation of the blood during the apneic period of paralysis and allows the physician longer to intubate him successfully.

In healthy adult volunteers who have been pre-oxygenated for 3-5 minutes, the average desaturation time (oxygen saturation <90%) is approximately 8 minutes.

This time is significantly shorter in patients who are critically ill and have a much higher metabolic oxygen demand.

Use the least amount of assistance necessary to obtain good oxygen saturation and adequate pre-oxygenation.

High-flow oxygen through the non-breathable mask may be appropriate for a patient with good respiratory effort.

High-flow oxygen through a well-fitting bag-valve-mask without additional positive pressure (i.e., squeezing the bag) may be necessary for those with increased respiratory compromise.

High-flow oxygen through BVM with positive pressure assistance (squeezing the bag) is used only when needed.

Apneic oxygenation

It is important because pulmonary blood flow still occurs during the apneic period of TTE placement.

Oxygen continuously diffuses out of the epithelium of the alveoli at 250 ml / min and into the capillary endothelium where it adheres to circulating hemoglobin.

Although there are no ventilations, there is a real flow and movement of oxygen through these concentration gradients.

This is because the alveoli are somewhat subatmospheric and a massive flow of gas (oxygen) circulates from the airways into the alveoli.

The RSI dictates this by assuming a full stomach unless oxygen saturation is low after the patient is paralyzed.

By applying NC at 15 L / min (harmful and otherwise not tolerable in the awake patient), the proximal airways can approach an FiO2 of 1.0 and serve to replace oxygen in the alveoli.

They have shown that apneic oxygenation through a NC during RSI is positive compared to those without this technique desaturated in 6 minutes.

Pretreatment

Pretreatment agents can be used to mitigate the physiological response to laryngoscopy, induction, and paralysis, which may be undesirable in certain clinical situations.

Note that although clinical dogma has supported their use in the past, the evidence in the literature is deficient in this area and because of this these are mentioned from a historical perspective.

Pretreatment medications are usually given 2-3 minutes prior to induction and paralysis.

These medications can be remembered through the use of memory load (ie, lidocaine or opioid pain reliever).

Lidocaine

Lidocaine (1.5 mg / kg IV) can suppress the cough or gag reflex experienced during laryngoscopy.

It has been considered to play a role in blunt increases in mean arterial pressure (MAP), heart rate (HR), and 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.

It can also be considered as part of the RSI for patients in whom the increase in MAP could be harmful (eg aortic aneurysm).

However, studies do not consistently demonstrate the effectiveness of lidocaine for these indications in patients in the emergency department (ED).

Based on this lack of evidence, no statement can be made regarding its absolute indication.

Opioids

The opioid analgesic (fentanyl 3 mcg / kg IV) mitigates the physiologic increase associated with direct laryngoscopy (ie, blunting increases blood pressure, heart rate, and mean arterial pressure).

One author recommends this in patients with high suspicion of ICP, although some data also suggest that these agents may increase ICP.

Opioid analgesics may also be helpful in patients with an aortic emergency (eg, aortic dissection or leaky aortic aneurysm) in whom blood pressure spikes should be avoided.

At this time, no conclusive evidence supports the use of opioids in RSI.

Positioning

In trauma cases where cervical spine injury is suspected and not yet ruled out, intubation should be performed without head movement.

Immobilization is best provided by an experienced assistant. In cases where cervical injury is not a concern, correct head positioning greatly improves visualization.

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

Three-axis theory: OA, PA and LA

In the three-axis theory OA is the oral axis, PA is the pharyngeal axis, and LA is the laryngeal axis.

Place the patient in the sniffing position for proper visualization; flex the neck and extend the head. This position helps align the axes and makes it easier to see the glottic opening.

Studies have shown that simple head extension alone (without neck flexion) was as effective as the sniff position in facilitating endotracheal intubation.

Complications

Complications include:

  • Pneumothorax.
  • Trauma dental.
  • Post-intubation pneumonia.
  • Vocal cord avulsion.
  • Failure to intubate.
  • Hypotension .
  • Aspiration.
  • Difficult assessment of the airway.

Preparation

Confirm that the intubation equipment is functional.

Assess the patient for difficult airway. If the patient meets the criteria for a difficult airway, rapid sequence intubation (RSI) may be inappropriate.

Non-dialysis procedures can be an alternative. The assistance of anesthesia personnel may be warranted.

Then these indications should be taken:

  • Establish intravenous access.
  • Prepare essential drugs and determine sequence of administration (induction agent followed immediately by paralyzing agent).
  • Review the possible contraindications of the medications.
  • Attach the necessary monitoring equipment.
  • Check the endotracheal tube (ET) cuff for leaks.
  • Make sure the bulb works on the blade of the laryngoscope.

Preoxigenación

Administer 100% oxygen through a non-respirator mask for 3 minutes to remove nitrogen. This is done without positive pressure ventilation using an airtight seal.

Although rarely possible in the emergency situation, the patient can take 8 vital capacity breaths (as deep as possible) of 100% oxygen.

Studies have shown that this can prevent apnea-induced desaturation for 3-5 minutes.

Assist ventilation with the bag-valve-mask (BVM) system only if necessary to obtain oxygen saturation = 90%.

Pretreatment

Consider administering medications to mitigate adverse effects associated with intubation.

Induction paralysis
  • Administer a fast-acting induction agent to produce loss of consciousness.
  • Administer a neuromuscular blocking agent immediately after the induction agent.

These medications must be given as an intravenous injection.

Protection and positioning

Although clinical dogma dictates that the Sellick maneuver be initiated to prevent regurgitation of gastric contents, there is a lack of literature to support this technique and it may in fact impede laryngeal vision.

This maneuver should be initiated by observing the beginning of unconsciousness.

Always maintain pressure throughout the intubation sequence until the position of the ET tube is verified.

Note that adequate laryngeal view has been shown to be best achieved by the bimanual method and should be used if the Sellick maneuver does not reveal the vocal cords.

Classical teaching dictates that cricoid pressure decreases the risk of gastric regurgitation in the lungs. However, in a study by Smith, the esophagus was partially lateral to the trachea in more than 50% of the subjects.

Furthermore, in an ultrasound study, 29 of 33 esophagus were partially displaced to the left of the trachea.

In a meta-analysis, Butler and Sen showed that there is little evidence to support the notion that cricoid pressure decreases the risk of aspiration in RSI.

Trial placement

Visualize the ET tube passing through the vocal cords and confirm tube placement.

Observe the color change on a qualitative carbon dioxide device at the end of the tide or use a continuous carbon dioxide monitor (ET-CO2).

Point auscultation method

Listen to each lateral lung field, the left axilla, and the left supraclavicular region for good breathing sounds. There should be no air movement over the stomach.

Two pilot studies have shown that ultrasound can reliably detect passage of a tracheal tube into the trachea or esophagus without inadvertent ventilation of the stomach.