Introduction:
Airway surgery is a peculiar situation in anesthesia in that the anesthesiologist must share the airway with the specialist in a highly coordinated manner. Anesthesiologists must balance two significant goals: minimizing obstruction of the surgical field while preserving patient oxygenation and ventilation. More importantly, one must always customize the anesthetic plan to address the difficulties associated with managing a critical airway before surgery, a disrupted airway during surgery, and a tenuous airway after surgery.
Many airway surgeries were carried out with topical anesthesia and patients spontaneously breathing inhalational agents a half-century ago, before the introduction of double-lumen tubes (DLTs) and modern anesthetic agents. Because of advances in surgical techniques and seminal works by Hermes Grillo and other researchers, most airway surgery can now be conducted successfully under general anesthesia with a secured airway and muscle relaxation, resulting in a stable and quiet surgical environment. Various airway and anesthetic management strategies have been developed based on the nature of the lesion, varying from cross-field ventilation to endobronchial intubation to jet ventilation. With the rapid advancement of minimally invasive and robotic techniques over the last few decades, there has been a renewed interest in performing operations without instrumenting airways in non-intubated processes. The accumulation of extracorporeal support experience has also opened up a new avenue for performing surgery on previously inoperable patients.
What Is the Basic Airway Management?
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While preparing for airway control, the following basic maneuvers are used: preoxygenation procedures, including airway obstruction relief with chin lift and jaw thrust, and insertion of a nasal or oral airway.
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Bag mask ventilation with an oropharyngeal or nasopharyngeal airway is a challenging technique to master. Two people best perform it with a better mask seal and jaw thrust, but it can quickly inflate the stomach.
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Techniques that squeeze the bag with one hand produce considerably smaller tidal volumes than two-handed techniques, with no significant difference in peak or average airway pressure. Large oral or nasal pharyngeal airways are the second element of optimal mask ventilation.
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Compared to the manual circle system with bag-valve-mask ventilation devices, ventilation-pressure-controlled mask ventilation lowered inspiratory peak flow rates and airway pressures, offering extra patient safety by reducing the chance of regurgitation and successive pulmonary aspiration.
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Endotracheal intubation requires preoxygenation in all patients. Preoxygenation in a patient with an expected difficult airway offers the maximum length of time a patient can tolerate apnea and gives the anesthesia provider resolve a difficult airway management issue. One of the standard preoxygenation techniques, such as tidal breathing of 100 percent oxygen for three to five minutes, is advised and effective in delaying arterial desaturation during tracheal intubation.
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Before induction of anesthesia, various preoxygenation procedures have been proposed, such as tidal volume breathing of 100 percent oxygen for three to five minutes, four deep vital capacity breaths of oxygen taken within 30 seconds, or eight deep vital capacity breaths of oxygen taken within 60 seconds.
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Preoxygenation is also important for critically ill patients. Still, the standard preoxygenation technique was only marginally successful in these patients, with only a slight improvement in blood oxygen tension as a surrogate marker of effective preoxygenation.
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A 25-degree head-up position may enhance preoxygenation efficiency in morbidly obese patients. This position improves gas exchange by minimizing atelectasis and ventilation or perfusion mismatch due to a lower functional residual capacity and increasing the desaturation safety period.
What Is the Advanced Airway Management?
The Fiberoptic Intubation Technique:
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Fiberoptic intubation (FOI) is a well-established technique for a patient with an expected difficult airway. When a difficult airway is expected, guidelines on anticipated difficult airway management emphasize the importance of the FOI technique.
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Awake intubation must then be assumed to keep the patient oxygenated, and the FOI technique remains the ‘gold standard’ in this situation. The FOI technique can be utilized for both oral and nasal laryngeal approaches.
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The FOI technique is attractive because it requires minimal cervical movement to achieve DTI in cervical spine disease or trauma. It allows for a post-intubation neurologic evaluation in cooperative patients when an awake tracheal intubation technique is used.
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The FOI technique helps treat patients with a small inter-incisor distance or ear, nose, and throat cancer. The acquisition of skills in this procedure is necessary for anesthetic training.
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In an unexpectedly difficult airway, however, oxygenation is the top priority. Thus, oxygenation devices are initially required, and FOI may be considered a secondary technique when oxygenation is already secured.
The Laryngeal Mask and the Intubating Laryngeal Mask:
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The laryngeal mask airway (LMA) is a significant advancement in airway management integrated into difficult airway algorithms. The LMA allows for ventilation and oxygenation while not entirely protecting against aspiration.
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The intubating laryngeal mask airway (ILMA) is a device that allows for adequate ventilation and guides blind intubation in patients with normal and abnormal airways. To overcome challenges in intubation with the LMA, the ILMA has several potential advantages.
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The ILMA is effective for ventilation and blind intubation in emergency patients with normal airways, and its application can be learned quickly. In addition, the ILMA has been used successfully in obese patients and patients with difficult airways.
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Furthermore, the ILMA had a comparable high success rate for tracheal intubation compared to the fiberscope technique, but the ILMA was associated with significantly fewer adverse events, particularly oxygen desaturation.
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As a result, the ILMA is a valuable tool in the cannot intubate and cannot ventilate situation or in a patient with unexpectedly difficult tracheal intubation to maintain oxygenation. The device's importance is emphasized in algorithms and guidelines from many anesthetic societies.
Cricothyroidotomy:
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Cricothyroidotomy should always be regarded when the patient has a compromised airway and unsuccessful intubation attempts. This procedure includes a surgical cut-down to the cricothyroid membrane and the insertion of a properly sized tracheal tube.
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The technique enables efficient ventilation while overcoming the drawbacks of percutaneous transtracheal needle ventilation. There are several cricothyroidotomy kits available.
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In contrast to direct puncture, the Seldinger technique reduces the risk of adverse events such as intratracheal bleeding, pneumothorax, pneumo-mediastinum, and esophageal puncture.
Transtracheal Jet Ventilation:
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Percutaneous transtracheal jet ventilation allows for transtracheal ventilation and oxygenation of the lungs. The procedure consists of percutaneously puncturing the cricothyroid membrane and inserting a large-bore intravenous catheter into the trachea.
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This procedure involves a jet injector powered by a regulated oxygen source. It can be conducted with multiple devices, such as a venous or arterial catheter, or a specific needle, such as the Ravussin needle.
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This procedure has to be incorporated into complex airway management, like cricothyroidotomy and may solve a glottic or subglottic problem such as a tumor, abscess, or hematoma.
Conclusion:
A patent and secure airway are required to manage anesthetized or critically ill patients. Regardless of the clinical setting (planned surgery or case of emergency airway management), maintaining oxygenation during tracheal intubation is the cornerstone of difficult airway management and is always emphasized in algorithms and guidelines. Although the occurrence of adverse respiratory outcomes in claims for injuries due to inadequate ventilation has decreased, claim reports emphasize that airway emergency airway or tracheal extubation and recovery of anesthesia phases are still related to death or brain damage, suggesting that it is necessary to be cautious during any such procedure.
