MANAGEMENT OF AIRWAYS IN THE TRE-HOSPITAL AREA
Most of the principles of pre-hospital airway control are identical to those that apply in the Emergency Department (ED). However, local protocols, the availability or not of drugs for neuromuscular block, limited equipment, and the need to transport the patient lead to considerations different from those of the Emergency Department.
The decision to intubate
In an out-of-hospital setting, the decision to intubate is made based on the same considerations that are made in ED. The first step consists in a rapid evaluation of the patient with particular attention to the airways and ventilation. If the patient holds his breath, if the protective mechanisms of the airways are intact, if the ventilation and oxygenation are adequate, it is not necessary to intubate. In the opposite case, intubation is necessary, unless the problem can be solved by using supraglottic devices suitable for both oxygenating and intubating. If intubation is considered mandatory, the emergency physician, in possession of the specific qualifications and qualifications envisaged for training, training and certification, may decide to obtain advanced invasive airway control,
In cases of mandatory intubation and possession of the specific requisites and qualifications provided for training, training and certification, the health care worker may use the videolaryngoscopic technique (if a videolaryngoscope is available: Glidescope, Airtraq, Storz C- Mac, King vision, McGrath, C-Mac, Vimac, etc.) or second generation supraglottic devices: Intubating Laryngeal Mask Airway (ILMA), Cobra perilaryngeal airway (CobraPLA), Combitube, King Laryn- geal Tube ( LT), Proseal Laryngeal Mask Airway (PLMA), I-Gel, LMA Supreme, Air-Q, Ambu Aura Once, Streamlined liner of the pharynx airway, Baska Mask, Ambu AuraGain, Total Track Video -Laryngeal Mask, etc.
A. Does the patient breathe well?
If the patient does not breathe well (obstruction, noisy breathing) or does not breathe at all (deep unresponsive coma or apnea), the head can be hyperextended and the jaw subluxated, unless there are contraindications (trauma with possible cervical damage ). The force on the jaw must be applied with the little finger in such a way as to keep the other four fingers free (eg for the face mask). The face mask should be used when the patient, despite the maneuvers described above, does not resume breathing. If even the mask ventilation is inadequate, the patient should be intubated as quickly as possible.
B. Are the airways protected?
After ensuring adequate ventilation, the next step is to assess whether the airways are protected from possible aspiration. Aspiration of gastric contents is a very serious complication that must be prevented. The inability to maintain the airway indicates a loss of protective airway mechanisms. In these cases it is appropriate to administer: naloxone (0.4-2 mg), opioid antagonist, and glucose (25 g) to prevent possible hypoglycaemia. If these drugs fail, mask ventilation and intubation should be continued.
C. Are ventilation and oxygenation adequate?
If the patient is breathing and if the protective mechanisms of the airways are intact, the next step can be taken: assess the adequacy of ventilation and oxygenation. If oxygenation is inadequate, as can occur in the case of pulmonary edema, it is sufficient to administer oxygen with the non-rebreather mask. If it is not possible to establish adequate oxygenation then the patient must be ventilated with a face mask and intubated.
D. Other considerations.
In some patients intubation is indicated despite adequate breathing, airway protection, ventilation and oxygenation. An example can be represented by pulmonary edema even with 90% oxygen saturation. In this case, if transport to the hospital takes a long time and if the patient does not respond to treatments, intubation may be adequate before the development of overt hypoxemia. Another example may be an overdose patient who is losing consciousness, a cyclic antidepressant overdose patient who has a generalized seizure, or cases of upper airway trauma with heavy bleeding or rapid expansion of a life-threatening hematoma of the patient. In these cases it is necessary careful evaluation and consultation with other doctors. In most cases, rapid transport to the hospital with supplemental oxygen via the non-rebreather mask is sufficient. But in some circumstances intubation may be the most prudent and indicated thing.
On field intubation
Once the decision to intubate has been made, the best method must be chosen based on the patient, personal experience and the means available. The choice also depends on the availability or not of myorisolving drugs and on the possibility of doing a cricothyrotomy. The choice to be made between orotracheal intubation or blind nasotracheal intubation. In both cases it is necessary to oxygenate the patient in a face mask before attempting intubation. If the upper airways are free (no trauma, foreign bodies or obstructions) and if the patient breathes spontaneously, blind nasotracheal intubation is recommended. Freediving constitutes a contraindication at the intubation nasotracheal at the blind because it is the respiratory sounds that guide the tube into the trachea. Even in the case of anatomical anomalies and foreign bodies, this technique is relatively contraindicated. Furthermore, blind nasotracheal intubation has a lower success rate and a higher complication rate when compared to intubation orotracheal. However, in some situations, blind nasotracheal intubation may be preferable: if the mandibular opening is narrow and it is not possible to use curaries and reversals, or if the patient is in a position that is not easily accessible for the operator (e.g. e.g. trapped in a car).
Orotracheal intubation with direct laryngoscopy is another important method for unresponsive patients and is the method of choice if the mandibular opening is not tight. The tube is inserted under direct vision of the glottis. Sometimes, in patients with a small mandibular opening it is preferable to administer drugs and proceed with orotracheal intubation rather than nasotracheal intubation.
If the patient is conscious and combative it is advisable to administer drugs to intubate. In these cases it is advisable to avoid blind nasotracheal intubation because if the patient resists, the risk of trauma during attempts to insert the tube increases. If the patient is not frankly comatose and does not oppose resistance, the ability to tolerate laryngoscopy should be assessed.
Methods of intubation
A. Blind nasotracheal intubation
The blind nose-tracheal intubation (INT) has been used a lot in the out-of-hospital setting but now, thanks to the introduction of drugs that facilitate the Oro Tracheal Intubation (IOT) the INT is clearly decreasing. The INT blindly presents two main indications. The first includes all those circumstances in which direct laryngoscopy and visualization of the glottis are impossible. An example would be that of a patient trapped in a car after a collision with another vehicle who needs to be intubated before being extracted from the car. In this case blind INT could be the only applicable method. The second indication is in the case of a narrow buccal opening. A small number of patients have a high tone of the masseter even in a state of unconsciousness and inadequate breathing. The opportunities that present themselves in this case are two: sedate and attempt the IOT or perform the INT blindly.
In principle, INT should not be performed in patients with asthma, COPD or pulmonary edema unless IOT is impossible. In fact, in these patients, prolonged blind attempts at INT could worsen oxygenation and therefore hypoxemia leading to respiratory arrest. However, the operator can choose to perform the INT also in patients with asthma, the important thing is to know that prolonged or traumatic attempts can worsen the patient’s condition.
B. Sedation intubation
The IOT it is performed in direct laryngoscopy. In some patients, however, laryngoscopy cannot be performed without administering drugs such as sedatives alone or with curaries. An increasing number of operators are using these drugs in the out-of-hospital setting to facilitate intubation: both the helicopter rescue and emergency transport teams are gaining more and more experience in the use of curaries. However, pharmacological protocols vary in different systems.
In principle, the patient is sedated when he is not cooperative enough for intubation, when he has a limited buccal opening or when there is no adequate mandibular relaxation.
In these cases, as long as the patient is intubated, drugs such as midazolam, diazepam, lorazepam and others can be used. In systems where the use of neuromuscular blockers is foreseen, a protocol of indications and methods of administering these drugs is usually available. Neuromuscular blocking drugs should be administered together with sedatives to avoid the patient’s physiological and psychological stress during intubation.
C. New tools for airway control.
In the last few years, various tools have been developed for the control of airways.
1. Laryngeal Mask Airway. AML is inserted blindly into the oropharynx and the technique is fairly simple to learn. Although the LMA does not protect airways air from the suction, allows you to ventilate patients effectively. In addition, the patient can be intubated through the AML, a maneuver to be performed in the ED. The AML is available in both reusable (which can be sterilized) and disposable (preferable) form.
2. Combitube. The Combitube is a tool developed for difficult airway situations in emergencies. The instrument is inserted blindly into the orophageal and positioned in the esophagus, then the two headphones (pharyngeal and esophageal) are inflated and the patient can be ventilated through the esophageal lumen. The training in the use of the Combitube is relatively easy and short. The Combitube can also be used in particularly difficult circumstances (patient trapped in a vehicle).
3. Bright stiletto. Intubation through a luminous stylet is a method light-guided. Experience with this technique it is still limited in the out-of-hospital setting although it is relatively easy to learn and could be a useful addition to direct laryngoscopy for oral intubation.
D. Failed intubation
An evaluation of the patient’s airways allows to know in advance the difficulty of intubation. If a difficult airway is anticipated it may be more prudent to quickly transport the patient to the ED for definitive therapy, rather than remain in the field attempting an intubation which is likely to fail. It is essential to evaluate the time required for patient transport in determining whether it is appropriate to perform an intubation under sedation. The first thing to do in case of intubation failure is to ventilate the patient with a face mask. Rescuers must be proficient with the face mask and must be able to use both the one-handed and two-handed techniques. If adequate ventilation and oxygenation cannot be obtained with the face mask, the patient must be repositioned, subluxation of the mandible must be performed again and the mask must be reapplied, paying attention to cover the mouth and nose and to keep it adherent to the patient. Then the ventilation is started and if the patient can be oxygenated it is advisable to quickly transport the patient to the hospital. It is important to understand why intubation fails. Maneuvers that can help in such situations are: patient repositioning and use of second generation supraglottic devices. It is important to know maneuvers such as the BURP (BURP maneuver: backward, upward, and rightward pressure on the larynx), introduced by Knill in 1993; this maneuver can help in both laryngoscopy and intubation.
Tips and advice
It is always good to properly assess the risks and benefits of field intubating or transporting the patient to ED in the field. There are very rare emergency cases in which it is not possible to ventilate the patient with the face mask until arriving in the ED. If a long journey is envisaged, it may be necessary to use curaries, but only and only when we have the reversal (Sugammadex) available. New instruments such as the AML or the Combitube can play an important role in airway control in the field. Everything should be evaluated on the basis of one’s experience in the field.
Where, in the course of the management of the complex acute patient, with a high level of clinical criticality, therefore characterized by severe clinical instability of vital functions, the emergency doctor, in possession of the specific qualifications and qualifications provided for training, training and certification, decides to achieve advanced control of the airways by invasive route, by means of gold / naso-tracheal intubation technique, it is possible to use the clinical-therapeutic protocol indicated by the guidelines of the Difficult Airway Society (Difficult Airway Society 2015 guidelines for management of unanticipated difficult intubation in adults British Journal of Anesthesia, 115 (6): 827–48 (2015); guidelines recommending the use of rocuronium, as a first choice curare, and sugammadex as a reversal, rather than neostigmine + atropine.
All the literature of the last ten years agrees that for the safety and quality of patient care the use of Sugammadex is recommended instead of the Neostigmine + Atropine mixture.
The rationale is as follows:
X decurarizing mixture, composed of neostigmine and atropine, has an onset of 5-10 minutes and a duration of action of about 45 minutes;
x the “standard” decurarizing mixture is usually composed of 5 ampoules of neostigmine (2.5 mg) + 2 fl of atropine (1 mg);
x the big problem with this mixture are the side effects, minimized in part by the addition of atropine, in particular increased bronchial secretions and increased risk of silent regurgitation.
Acetylcholine, like important neurotransmitter of the system nervous autonomic parasympathetic, also acting on muscarinic receptors, hence the adverse effects of neostigmine:
x severe bradycardia;
x increased bronchial secretions;
x increased risk of aspiration;
x increased gastric secretion and peristalsis;
x bladder spasm;
x paradoxical weakness (after recovery from neuromuscular block, further doses of neostigmine cause diaphragm weakness);
x post-operative residual curarization.
Sugammadex has a rapid onset and offset, almost no side effects, but above all complete recovery at any time from the administration of curare. The drug is extremely safe for these characteristics:
X no changes in heart rate and blood pressure or other cholinomimetic activities;
x it is not metabolised, but completely excreted in 24-48 h;
x the acid-base balance does not affect the speed of recovery;
x it has no interference with other non-steroidal muscle relaxants.
Simplified rapid sequence intubation for the out-of-hospital environment.
A.1. Prepare the necessary and ensure that the patient is in an appropriate environment for intubation.
B. 2. Pre-oxygenate the patient with the non-rebreather mask for at least three minutes if possible.
C. 3. Pre-treatment drugs (rarely used). Recommendation: lidocaine 1.5 mg / kg iv in the case of head trauma, reactive pathologies of the airways.
D. 4. Paralysis and sedation (Propofol and Rocuronium if Sugammadex is available).
E. 5. Sellick maneuver if the team is confident with the maneuver and deems it necessary.
F. 6. Placement of the tube in the trachea. Confirm tracheal positioning, fix tube, transport patient.