Airway management may be one of the essential 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 tricky. 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.
- Failure 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 endotracheal tube intubation (ETTI) method in the emergency department (ED). It produces rapid unconsciousness (induction) and neuromuscular blockade (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 (e.g., ketamine, etomidate ).
This is immediately followed by a paralyzing agent (e.g., 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 safe and effective in EDs over the past four 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 is 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.
In a patient with a suspected difficult airway, RSI should be approached with caution. A wakefulness technique or airway adjuncts (e.g., fiberoptic intubation) are recommended if difficulties are anticipated.
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 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 horrible experience must be studied and monitored.
Randomized prospective studies are needed to define the use of prehospital IHR better.
The ubiquitous use of video-assisted laryngoscopes (Vous) in EDs has been shown to reduce complications in RSI.
Similar results may be shown as more prehospital personnel are trained in this modality.
Compared to direct laryngoscopy, the amount of training required in VAL is less and glottic visualization is 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 part 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.
- Failure to maintain the tone of the airways.
- It is swelling of the upper respiratory tract, as in anaphylaxis or infection.
- Facial or neck trauma with oropharyngeal hemorrhage or hematoma.
- It decreased consciousness and loss of airway reflexes.
- Lack of protection of the respiratory tract against aspiration.
- Decreased consciousness leads to regurgitation of vomit, secretions, or blood.
- Do not ventilate.
- The result of failure to maintain and protect the airways.
- Prolonged respiratory effort results in fatigue or loss, as severe asthma or COPD.
- Not oxygenate (carry oxygen to the pulmonary capillary blood).
- The result of lack of maintenance and protection of the respiratory tract or lack of ventilation.
- Diffuse pulmonary edema.
- The acute respiratory distress syndrome.
- Extensive pneumonia or airspace disease.
- Pulmonary embolism
- Cyanide toxicity, carbon monoxide toxicity, methemoglobinemia.
- Anticipated clinical course or deterioration (e.g., Need for situational control, tests, procedures).
- Uncooperative trauma patient with life-threatening injuries requiring procedures (e.g., 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.
- Total upper airway obstruction, requiring a surgical airway.
- Complete loss of facial/oropharyngeal landmarks, requiring a surgical airway.
The anticipated “difficult” airway, in which endotracheal intubation may be unsuccessful, depends 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 assess the airway and risk of difficult intubation (e.g., 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 maybe flaccid; there is no time for preoxygenation, pretreatment, or induction and paralysis.
The kit includes the following:
- Laryngoscope handle, No. 3 Macintosh (curved) blad.
- Laryngoscope handle, n. Macintosh sheet 3 (curved) and No. 3 Miller blade (straight).
- Endotracheal tube (ET).
- Syringe, 10 ml (to inflate the balloon with an ET tube).
- A suction catheter (e.g., Yankauer).
- Carbon dioxide detector (e.g., Easycap).
- Oral and nasal airways.
- Ambu bag and mask are attached to the oxygen source.
- Nasal cannula.
It is essential 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.
Rapid sequence intubation (RSI) is based on administering 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.
Pre-oxygenation is performed with high-flow oxygen through a non-breathable mask for 3-5 minutes before 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 enables 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 critically ill patients with 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 reasonable 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.
It is essential 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 natural flow and movement of oxygen through these concentration gradients.
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 a FiO2 of 1.0 and serve to replace oxygen in the alveoli.
They have shown that apneic oxygenation through an NC during RSI is favorable compared to those without this technique desaturated in 6 minutes.
Pretreatment agents can mitigate the physiological response to laryngoscopy, induction, and paralysis, which may be undesirable in clinical situations.
Note that although clinical dogma has supported their use in the past, the evidence in the literature is deficient in this area. Because of this, these are mentioned from a historical perspective.
Pretreatment medications are usually given 2-3 minutes before induction and paralysis.
These medications can be remembered through memory load (i.e., lidocaine or opioid pain reliever).
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 sharp 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 part of the RSI for patients whose increase in MAP could be harmful (e.g., 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.
The opioid analgesic (fentanyl three mcg/kg IV) mitigates the physiologic increase associated with direct laryngoscopy (i.e., 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 (e.g., 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.
In trauma cases where cervical spine injury is suspected and not yet ruled out, intubation should be performed without head movement.
An experienced assistant best provides immobilization. In cases where the cervical injury is not a concern, correct head positioning significantly 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.
- Trauma dental.
- Post-intubation pneumonia.
- Vocal cord avulsion.
- Failure to intubate.
- Hypotension .
- Complex assessment of the airway.
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 the 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.
Administer 100% oxygen through a non-respiratory mask for 3 minutes to remove nitrogen. This is done without positive pressure ventilation using an airtight seal.
Although rarely possible in an emergency, the patient can take eight 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%.
Consider administering medications to mitigate adverse effects associated with intubation.
- 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. It may 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 the bimanual method best achieves adequate laryngeal view 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 esophagi were partially displaced to the left of the trachea.
In a meta-analysis, Butler and Sen showed little evidence to support the notion that cricoid pressure decreases the risk of aspiration in RSI.
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.