Ease of Intubation with McGrath Videolaryngoscope and Incidence of Adverse Events During Tracheal Intubation in COVID-19 Patients: A Prospective Observational Study

The novel coronavirus COVID-19 has caused a pandemic of previously unimaginable proportions. Highly infective, it is leading to an extremely high absolute burden of morbidity and mortality, primarily due to hypoxic respiratory failure, hemodynamic instability, reduced oxygen stores and increased oxygen consumption [1]. Many patients with COVID-19 were in critical condition and require intubation, an aerosol-generating procedure with a high propensity to generate enormous viral loads [2]. Moreover, increased risk of aerosol transmission during airway management is also possible due to the proximity of the intubator to the patient's airway [2,3]. During the SARS outbreak in 2003, healthcare workers who performed aerosol-generating procedures such as tracheal intubation had a higher likelihood of contracting the disease, compared to non-intubator [4]. Therefore, certain attending healthcare providers like anesthesiologist, intensivists, and emergency physicians are particularly at higher risk of nosocomial infection not only due to the aerosolization of the virus during tracheal intubation but also due to increased duration of exposure [5,6].

Tracheal intubation in critically ill patients remains high-risk despite advances in equipment, technique, and clinical guidelines. Peri-intubation cardiac arrest occurs in about 1% of cases and is highly associated with peri-intubation oxygen desaturation and hypotension [7]. Moreover, hypoxemia and hemodynamic instability before intubation are associated with increased risk of complications. Videolaryngoscopy therefore becomes an important tool in anticipated and unanticipated difficult intubation. Videolaryngoscopes (VL) are designed to improve visualization of the glottis, increase first attempt intubation success rate, reduce intubation related complications, and minimize exposure by increasing the distance between the operator and the patient's oral cavity [8]. The transition to videolaryngoscopy as a routine first line option through anesthetic and ICU practice has been reported and is currently suggested by many societies as a primary intubation device for COVID patients [9]. One such videolaryngoscope is the McGrath MAC (Aircraft Medical, Edinburgh, Scotland), a unique battery-powered device with attached screen and disposable laryngoscope blade that actually have made its worldwide importance in current pandemic.

We aimed to assess ease of intubation and first pass success with McGrath videolaryngoscope in COVID-19 patients. Secondary objectives were use of accessory maneuvers and incidence of major adverse events within 24 hours of intubation.

This prospective observational study was conducted from October 2020 to January 2022 after approval by institutional ethics review committee (ERC). We included all consecutive adults (>18 years old) suspected or confirmed COVID-19 patients undergoing emergent or urgent tracheal intubation by McGrath videolaryngoscope and excluded any patients undergoing intubation for general anesthesia. Study locations included the Intensive Care Unit (ICU), Acute Care Unit (ACU), Emergency Room (ER) and COVID ward at the Aga Khan University Hospital, Karachi. Waiver of patient consent was obtained from ERC. Each patient was coded through a computer-generated patient identification number (PIN) and no identifiers like patient name, initials or hospital record numbers were used. Data was collected via an online form and anesthesiologists performed tracheal intubation were requested to fill. We identified data coordinators among investigators who contacted the consultants on COVID intubation calls. The data coordinators were responsible for data collection regarding complications and adverse events by follow up of patients at 24 hours after intubation through bedside visit and chart review.

The primary outcome was to determine ease of intubation by first pass success using McGrath VL in COVID-19 patients outside operating room. Secondary outcomes included best glottic view by percentage of glottic score (POGO), use of accessory maneuvers, adjuncts used, number of intubation attempt and major adverse events during and within 24 hours of intubation [10]. Data was collected through anonymized online form. This included patient characteristics (Age [more than or less than 65 years], gender), comorbidities, patients COVID status, ongoing oxygen therapy before intubation, patient position for intubation, induction technique (classic or modified rapid sequence induction), rescue devices or techniques, and time taken to successfully pass endotracheal tube. Classic RSI mainly consists of preoxygenation, administration of short acting anesthetic/sedative agents, rapidly acting muscle relaxant, application of cricoid pressure, laryngoscopy and inserting a cuffed endotracheal tube to secure the airway. Modified rapid sequence induction (RSI) is implemented in an attempt to optimize patient outcomes and reduce excess risk exposure [11]. In addition to above components of classic RSI, the modification may include use of short acting opioids, ketamine or lidocaine, use of positive pressure ventilation before passing tracheal tube or apneic oxygenation. Glottic view taken according to modified POGO score as full (100%), partial (50%) and nil (0%). Ease of intubation was described as easy (ETT passed in first attempt), Modified (ETT passed with more than one attempt, or a modified technique or adjunct used) and unachievable (unable to pass ETT). Accessory maneuver was defined as external laryngeal manipulation or use of Magill forceps, or both required to facilitate passage of endotracheal tube through glottic opening. Hypoxemia defined as oxygen saturation (SaO2) <90%. Hypotension was described as having a systolic blood pressure of less than 90 mmHg or mean arterial pressure (MAP) of less than 60 mmHg.

All analysis was performed using statistical packages for social science version 19 (SPSS Inc., Chicago, IL). Clinical features of patients were characterized using descriptive statistics and comparisons of categorical variables was performed using chi-square or Fisher's exact test at a two-sided significance level of 0.05.

Patients with suspected or confirmed COVID-19 are at greater risk for complicated intubation because not only is it a common occurrence that these patients decline rapidly due to a lack of inspiratory reserve, but strict hospital COVID infection control policies often make it difficult if not impossible to perform adequate airway evaluation or have the necessary number of supportive personnel present to assist when urgent intubation is required. Outside the operating room, tracheal intubation is commonly performed by personnel with less experience in airway management, compared to anesthesiologists, and this can make intubation more arduous of a task, potentially even compromising patient safety.

Videolaryngoscopy is becoming increasingly popular for use in both normal and difficult airways, especially since the beginning of the pandemic. The difficult airway algorithm developed by the American Society of Anesthesiologists (ASA) does not endorse nor discourage the use of videolaryngoscopy and instead leaves it to the anesthesiologist to decide if and when to use it [13]. Moreover, the Difficult Airway Society guidelines state that videolaryngoscopy use is dependent upon good clinical judgement, and that all anesthesiologists should have immediate access to videolaryngoscopes [14]. However, especially in an anticipated difficult airway, the advantages and practicality of videolaryngoscopy makes it an excellent tool for intubation, with some authors even recommending it for first line use in both normal as well as difficult airways [15]. Our data will be useful for future planning and management of such patients and help establish precautions for staff. The recommendations are urgently needed and will suggest good clinical practice for our local healthcare facilities

Our study exemplifies an overall high success rate of intubation with McGrath videolaryngoscope with only 2.9% of patients requiring more than two attempts to intubate successfully, which is comparable to the results of other studies. These studies reported 100% success with direct laryngoscopy in simulated difficult airway patients [16], 98–100% in patients with normal airway [17], and 95% of patients after failed direct intubation [18]. These high success rates are likely due to videolaryngoscopy facilitating the assistant as well at the time of intubation by allowing better shared visualization of the glottis, since both the screen and the blade can be viewed during insertion, without needing to align the oral, pharyngeal, or laryngeal axes. Moreover, it allows better coordination between the anesthesiologist and the assistant, and correction of laryngoscopic maneuvers if required.

Despite an overall success rate, accessory adjuncts and maneuvers were required to facilitate difficult intubation in 77.1% of patients, most of whom had full (80.95%) or partial (15.2%) glottic views, as opposed to 3.8% of patients with no glottic view, none of which were easy intubations. Three patients, all intubated via classic RSI, required more than two attempts with videolaryngoscope for intubation, as well as accessory maneuvers. The first was a female of less than 65 years with no known comorbid conditions, confirmed COVID, no glottic view and had required external laryngeal manipulation, ETT stylet and Bougie, as well as a change to conventional laryngoscope for successful intubation which took thirty seconds to one minute. There were no post intubation complications after 24 hours. Another immunocompromised male of less than 65 years with Diabetes Mellitus, no glottic view and confirmed COVID required External laryngeal manipulation, Bougie and face mask ventilation before successful intubation which took more than 2 minutes and had developed hypoxemia during intubation. Again, there were no post intubation complications after 24 hours. Lastly, one female of less than 65 years with chronic kidney disease, confirmed COVID, partial glottic view and had required External laryngeal manipulation and ETT stylet for successful intubation, which took one to two minutes, and had developed hypoxemia during intubation. 24-hour post intubation revealed mortality. Other studies have reported a 24h mortality of 10.4% [19]. These findings may be related to patient characteristics or events at tracheal intubation, but further analysis of this cannot be performed due to having only observational data.

More than half of all patients were intubated within 30 seconds and rest under a minute, portraying that the majority were intubated quickly. However, other studies show that use of videolaryngoscopy results in either no difference in time to intubation [20] or longer intubation time compared to traditional laryngoscopes [16,20].

Anesthesiologists in our study reported easy McGrath-assisted intubation in 92.4% of cases and were able to successfully intubate using the McGrath in all but seven patients, demonstrating a considerable advantage in difficult cases. One randomized control trial comparing six different videolaryngoscopes found the McGrath to have the highest first attempt intubation success rate [21,22].

The findings of our research demonstrate the effectiveness, feasibility and high rate of success using McGrath videolaryngoscope to facilitate tracheal intubation in suspected or confirmed COVID-19 patients. Videolaryngoscopy improve first attempt success in difficult airways and is recommended when available. We would suggest that McGrath VL with a disposable blade design is better suited for intubation in patients during the pandemic with highly infectious diseases.