Prognostic factors of intraoperative accidental extubation during laryngeal surgeries

Posted on by admin

RESEARCH ARTICLE

Hippokratia 2023, 27(4): 141-147

Marković D1, Šurbatović M2,3, Milisavljević D4,5, Marjanović V1,6, Stošić B1,6, Kovačević T4, Stanković M4,5 

1Clinic for Anesthesiology and Intensive Therapy of University Clinical Center in Niš, Niš
2Clinic for Anesthesiology and Intensive Therapy
3Faculty of Medicine
Military Medical Academy, University of Defence, Belgrade
4Otolaryngology Clinic, University Clinical Center in Niš
5Department Otorhinolaryngology
6Department Surgery and Anesthesiology and Reanimatology
Faculty of Medicine, University in Niš, Niš, Serbia

Abstract

Background: Head and neck surgery is considered high-risk for difficult intubation and accidental extubation. Laryngomicroscopy implies surgical manipulations at the level of the vocal cords. Also, this type of surgery demands a particular position for the patient during the whole surgical intervention. All of this makes accidental extubation even more possible.

Methods: We included a total of 100 patients scheduled for laryngomicroscopy in the study. We have assessed patients’ general and clinical data and provided necessary measurements. After the intubation, we documented the depth of the endotracheal tube at the level of the upper incisors and repeated the measurement after the surgical intervention. We recorded all possible difficulties encountered by the surgeon.

Results: We found a significantly more frequent tube dislocation in patients from the difficult intubation group, with χ2 =6.632, p =0.010. Inter-incisor gap (IIG) and modified Mallampati score showed statistical significance regarding tube dislocation, with p values of 0.002 and 0.047, respectively. There was statistical significance between tube dislocation and difficulties experienced by surgeons, with χ2 =13.504 and p =0.001. According to the area under the curve (AUC) at the Receiver operating characteristic (ROC) curve, the cut-off value for significant tube dislocation was 1.15 cm. When we divided the enrolled patients into two groups, below and above the cut-off value, the IIG maintained statistical significance with a cut-off value of 5.25 cm.

Conclusions: Modified Mallampati score and IIG are considered valuable parameters for rapid preoperative risk assessment of possible accidental extubation. The final depth of the endotracheal tube should be about two cm deeper than necessary, as long as there is adequate ventilation on both sides of the lungs. Difficult intubation undoubtedly represents a risk for accidental extubation occurrence. HIPPOKRATIA 2023, 27 (4):141-147.

Keywords: Unplanned extubation, risk factors, airway extubation, difficult intubation

Corresponding author: Marković Danica, Clinic for Anesthesiology and Intensive Therapy of University Clinical Center in Niš, 6/50 Josifa Pančića, 18000 Niš, tel.: +381652811411, e-mail: danica.markovic.1983@gmail.com

Introduction

Accidental extubation (AE) during surgical interventions is an extremely infrequent event. Loss of control over and the inability to re-establish the airway can lead to hypoxemia, hypotension, brain damage, cardiac arrest, and death. AE can occur during: surgical interventions, awakening from anesthesia, and in the intensive care unit1-5. The reported incidence of AE ranges from 0.5 % to 35.8 % in adults6,7. Risk factors for AE are patient movement, inadequate sedation, delirium, agitation, prone positioning, manipulation of the endotracheal tube, inadequate securing of the endotracheal tube, lack of extubation plan, etc8. In addition to the risks concerning patients, there are also risks concerning the surgical procedures and the anatomical region where the surgical intervention is performed.

The possibility of AE in patients with difficult airways requires special attention. Head and neck surgery is characterized as high-risk for difficult intubation, and ear, nose, and throat (ENT) surgery very often implies the presence of tumor changes in the upper respiratory tract and adjacent tissues. Manual manipulation in the area adjacent to the intubated airway is unavoidable during ENT surgeries, and the anesthetist’s access to the airway is impossible after the surgical procedure commences. Therefore, ENT surgery is considered to have the highest risk of possible AE during surgical interventions9,10.

If AE occurs during the ENT surgeries, additional life-threatening complications can be anticipated. Previous difficult intubation may now become impossible due to induced edema or bleeding, the collapse of soft tissues during general anesthesia, the presence of a hematoma that compresses surrounding tissue, as well as laryngospasm10,11. Furthermore, extreme secretion and/or bleeding during intraoral procedures can result in aspiration and subsequent aspiration pneumonia. If the endotracheal tube cuff is still inflated when the tube is accidentally dragged out during the surgery, induced damage to the vocal cords and/or laryngospasm may be inevitable12.

We designed this study to include patients scheduled for diagnostic microscopic laryngeal surgery since it implies surgical manipulations at the level of the vocal cords. During this procedure, adequate visualization of the glottis is necessary, and this is achieved by extreme neck extension and the introduction of a rigid laryngoscope13. In most cases, introducing a rigid laryngoscope enables easy visualization of the vocal cords. However, in practice, a situation referred to as difficult laryngeal exposure is encountered. This condition necessitates different methods and advanced techniques to facilitate the surgeon’s work. These specificities of microscopic laryngeal surgery make this procedure high-risk for AE occurrence.

Our study aimed to determine which parameters and manipulations during intubation and surgical intervention can indicate an increased incidence of significant tube dislocation with possible damage to vocal cords and AE. Also, we wanted to facilitate the work of the ENT anesthesiologist in terms of accurate prediction of possible AE during surgery and to provide methods for securing the airway during surgical manipulations.

Materials and methods

One hundred patients were enrolled in this prospective clinical study conducted from June to November 2023 at the Clinic for Otorhinolaryngology in the University Clinical Center in Nis, Serbia. Inclusion criteria were set to enroll: i) patients over 18 years of age, ii) scheduled for microscopic laryngeal surgery, iii) under general endotracheal anesthesia, iv) for vocal fold lesion diagnosis, v) with an American Society of Anesthesiologists (ASA) class less than four (<4), and vi) without previous tracheostomy. We excluded based on the set criteria: i) children under 18 years, ii) patients undergoing emergency surgical interventions, iii) presence of a tracheostomy and cannula, iv) inability to understand and/or sign an informed consent or v) the patient’s unwillingness to participate in the study. The study was approved by the Institutional Ethical Committee of the Medical School, University in Nis, Serbia (decision No 12-6600/2-2, date: 08/06/2023).

All patients were informed in detail regarding the study and provided informed consent before the procedure. We recorded the following general data from patients’ medical history: age, gender, height, and weight, and calculated the body mass index (BMI) through the online interactive calculator14.

During the patient’s preoperative assessment, an anesthesiologist considered data regarding the presence of stridor, snoring or apnea episodes during sleep, and fatigue during normal daily activities. Physical examination gave an insight into the following measurements: inter-incisor gap (IIG), mandible length, anterior and posterior depth of the mandible, thyromental distance (TMD), neck length, and girth. We measured IIG with a simple ruler from the upper to lower incisors while the patients forced their mouths open to the maximum extent. Mandible length was measured, commencing from mental protuberance to the angle of the mandible. We measured the anterior depth of the mandible from the base of the lower incisors to the mental protuberance, while the posterior length was measured immediately behind the third molar to the lower mandible edge. The measurement of TMD was accomplished after instructing the patient to make a maximum neck extension, representing the distance between the thyroid cartilage and mental protuberance. The neck length was measured from mental protuberance to the jugular notch of the sternum while the patient’s head was still in maximum extension. Neck girth was measured at a point just below the larynx and perpendicular to the cephalocaudal axis of the neck. We recorded all of the measurements in cm and also assessed the following physical features: subluxation (S-lux), reclination, prognathism, retrognathia, the existence of prominent incisors, and modified Mallampati score. After instructing the patient to perform a maximal protrusion of the lower over the upper incisors, we assessed for S-lux existence. S-lux classification is determined by whether the lower teeth can move in front of the upper teeth (S-lux >0), the lower teeth can be placed in line with the upper teeth (S-lux =0), or the lower teeth can not be placed in line with the upper teeth (S-lux <0). Reclination was performed with the mouth maximally open and the upper teeth lined horizontally in relation to the ground. Then, the patient was instructed to perform maximal neck extension, and the deflection angle of the upper teeth was measured15. The modified Mallampati score was assessed according to official recommendations, and its interpretation is presented in Table 116,17. Every patient received premedication with midazolam 0.1 mg/kg and atropine 0.5 mg. Standard monitoring was applied after the patient’s transfer to the operating room, including electrocardiography, blood pressure monitoring, capnography, and pulse oximetry. During induction, we utilized midazolam 0.15-0.2 mg/kg, fentanyl 100 mcg, propofol 1-1.5 mg/kg, and succinylcholine 1 mg/kg. An endotracheal intubation was performed using a standard Macintosh laryngoscope blade while using a flexometallic tube of a small radius. After the external tube fixation, the depth of the endotracheal tube was measured at the level of the upper incisors, and the same measurement was repeated after the procedure of microscopic laryngeal surgery and after the necessary extreme neck extension performed by the surgeon. The second result was subtracted from the first, and the result was noted. Anesthesia was maintained with inhalational anesthesia, without any further relaxation needed since this surgical procedure is brief. If needed, propofol was added in aliquots of 20 mg or we added rocuronium in maintenance doses.

Immediately after the intubation, all the necessary parameters were noted in order to calculate the intubation difficulty score (IDS). Parameters needed for the calculation of the IDS score as well as details of calculation can be found in Table 2. The adequacy of the endotracheal tube placement was checked by lung auscultation.

We noted all the difficulties encountered and techniques employed by the surgeon, e.g., modification of patients’ position, elevation, external laryngeal pressure, change of rigid laryngoscope, replacement of surgeon, etc.

After checking data for normal distribution, we calculated the statistical significance utilizing Spearman’s rank-order correlation, the logistic regression model, Pearson’s χ2 test, simple logistic regression, and the Mann Whitney U test. Values are presented as mean ± standard deviation. We determined the area under the curve (AUC) to define the cut-off value of statistically significant scale parameters. We considered a p-value of less than five to be a statistically significant result. All statistical analyses were performed with the Statistical Package for the Social Sciences (SPSS) for Windows, Version 10.0 (SPSS Inc., Chicago, IL, USA). We calculated the study’s power using the G*Power program (Heinrich Heine Universitat Dusseldorf, Dusseldorf, Germany), estimating with a study power of 80 % and a probability of error of 0.05, the required number of 80 patients.

Results

This study included 100 patients aged between 24 and 84 years. A total of four patients were excluded from the study since intubation was not possible with traditional laryngoscopy and/or other methods for challenging intubation. The mean age of the 96 patients was 60.03 ± 11.82 years. Thirty-seven (38.54 %) patients were female, and 59 (61.46 %) were male. The mean BMI was 26.78 ± 5.39, which belongs to the overweight group. The mean patients’ height was 170.52 ± 9.56 cm, and the mean weight was 77.48 ± 18.48 (range: 40-146) kg. Demographic data are presented in Table 3. Thirty (31.25 %) intubations were described as difficult, according to the IDS score. Details about additional intubation methods, besides direct laryngoscopy, are presented in Figure 1.

Figure 1: Box plot showing the number of patients divided into different alternative intubation methods. It should be noted that different intubation techniques were sometimes used during intubation.

After performing the microscopic laryngeal surgery, the mean tube dislodgement of the endotracheal tube was 0.97 ± 0.74 cm with minimal dislocation of zero cm and maximum dislodgement of 3.7 cm. When statistically analyzed, there was significantly greater tube dislodgement in patients from the challenging intubation group (χ2 =39.159, p =0.026).

From all preoperatively measured and analyzed parameters, just IIG and Mallampati scores had statistical significance when measuring tube dislodgement during the procedure (p =0.002 and p =0.047, respectively; Table 4).

Also, a solid statistical significance was found between endotracheal tube dislodgement and difficulties experienced by surgeons during the surgical intervention (χ2 =13.504, p =0.001). Difficulties experienced by the surgeon in our research considered difficult visualization of the glottis. Methods used by the surgeon in order to overcome these difficulties were: change of the instrument, repositioning of the patient, external laryngeal pressure and change of surgeon. Details about the number of patients in each group are presented in Figure 2.

Figure 2: Box plot showing the number of patients in every group considering methods used by the surgeon to visualize the glottic area adequately. It should be noted that more techniques were sometimes used in one patient.

There was a strong statistical significance between the difficulty experienced by the surgeon during intervention and previous difficult intubation, according to the IDS score, with P=0.001.

We used the C statistics for tube dislodgement regarding challenging intubation to define the cut-off value that could be considered a significant tube dislocation. The cut-off value for significant tube dislocation from the AUC curve of 0.664 [p =0.010, 95 % confidence interval (CI): 0.552-0.776] was 1.15 cm with sensitivity of 53.3 % and specificity of 75.8 %. Then, we divided the enrolled patients into two groups, one above and one below the cut-off value of 1.15 cm for tube dislocation. The IIG parameter maintained statistical significance after the patient’s cohort division below and above the cut-off value (p =0.029). The AUC curve was 0.637 (p =0.030, 95 % CI: 0.519-0.754) with a cut-off value for IIG of 5.25 cm with a sensitivity of 40.6 % and specificity of 80.2 %.

Discussion

One of the ENT anesthesiologist’s main tasks is constantly monitoring ventilation adequacy and the endotracheal tube’s position during surgical interventions. The only available ways of monitoring the correct placement of the endotracheal tube are lung auscultation and monitoring of the intrapulmonary pressure, gas exchange, and oxygen saturation. When ENT procedures are concerned, it is essential to note that a leak caused by cephalad dislodgement of the endotracheal tube can often be confused with a punctured cuff during monitoring. The occurrence of the punctured cuff represents an unwanted but relatively common complication of laryngeal surgeries. If recognized in time, this complication is not considered a high risk for patients’ health17.

The first indications of tube dislocation that can be readily noticed are desaturation, loss of the end-tidal carbon dioxide graph, and the inability to ventilate the patient adequately. When AE occurs, the patient should be manually ventilated with 100 % oxygen. The patient should be reintubated as soon as optimal surgical conditions are met19.

Timely recognition of tube dislocation is extremely important. Okano et al have organized training for residents, including planning adequate procedures in case of AE occurrence during thyroidectomy. The goal of this training was timely recognition of tube dislocation, informing the surgical team about it, as well as re-securing the airway in a patient with a previous difficult airway20. Endotracheal tube displacement can occur caudal or cephalad, despite adequate tube fixation with adhesive tape. When it comes to ENT surgery, both types of endotracheal tube migration are possible due to changes in the position of the patient’s head. However, cephalad migration of the endotracheal tube can be expected mainly during microscopic laryngeal surgery. This cephalad migration can lead to a worrying airway leak, damage of the vocal cords or even AE18.

Accidental extubation is a rare but hazardous complication, and it is necessary to find parameters that may indicate a higher risk of its occurrence. Our study indicated tube dislocation and, thus, the chance of AE is higher in patients with smaller IIG, e.g., below five cm, and higher Mallampati grading. Ali et al presented a case report of AE during oral surgery in a patient who preoperatively had the following parameters that indicated possible difficult intubation: IIG below two fingers and Mallampatti grade four. Surgical manipulation of the head is highlighted as a possible cause of AE occurrence. This observation is in full correlation with our results21. Gupta et al also described a case of AE in which the IIG was limited to only three mm with the presence of severe retrognathia and micrognathia with reduced TMD. Our research did not show a statistical association of retrognathia and TMD with AE. These parameters indicated difficult intubation and were not crucial for the occurrence of AE in the case encountered by Gupta et al.

Several scientific papers have indicated the association between challenging intubation and AE during head and neck surgery7,21-22. The basic principle of microscopic laryngeal surgery is opening the oral cavity and trachea in the same plane to visualize the glottis adequately. Reduced opening of the oral cavity, low IIG, the necessity of external pressure on the trachea during intubation, and problematic intubation naturally indicate difficulties during surgical work and increase the possibility of AE.

In our institution, intubation for the purposes of microscopic laryngeal surgery is performed with flexometallic endotracheal tubes of small diameter. Flexometallic tubes are known to provide enhanced airway safety in terms of resistance to compression and bending19,23. However, the structure of the wire inside the tube affects the increased elastic recoil force of the tube and facilitates its upward pull during each manipulation19.

It is a fact that microscopic laryngeal surgery itself and extreme neck extension performed by the surgeon result in more frequent AEs. In the literature, it is found that tube migration in laryngology can amount to as much as 1.9 ± 0.7 cm, which is much higher than in our research24. This discrepancy can be explained by the fact that Tsukamoto et al included only 12 patients in the study, and they performed nasal intubation. Also, the measurement of tube dislocation was performed using the fiberoptic bronchoscope.

An IIG below 5.25 cm, a high Malampati score, and encountered problematic intubation may indicate difficult surgical conditions, more extended surgical manipulation during work, patient re-positioning, and a more frequent tube dislocation.

Considering the extremely high risk of AEs during laryngological interventions, it is recommended to consider the IIG and Mallampati classification for a rapid preoperative risk assessment. It is recommended that the depth of the endotracheal tube should be approximately two cm deeper than necessary, as long as there is adequate ventilation on both sides of the lungs. Auscultation should be frequent during the surgical intervention. Difficult intubation undoubtedly indicates a chance of AE occurrence.

There exist certain limitations of this study. The study should be expanded in the future since the number of patients is limited to 100. Preoperative measurements and evaluations were provided by one anesthesiologist and future research should include two or more anesthesiologists.

In conclusion, microscopic laryngeal surgery implies surgical manipulations both externally and in the glottic area. This represents a high threat for the occurrence of intraoperative AE. Anesthesiologist should use IIG below five cm and the class of modified Mallampati score in order to predict possible AE. After intubation, the endotracheal tube should be externally fixated approximately two cm deeper than needed as long as the lung auscultation is sufficient.

Conflict of interest

There are no conflicts of interest.

Acknowledgement

We thank Primarius Tatjana Kovačević, MD, PhD, Dragana Mitrović, MD, Tanja Cvetković, Senior OT technician, and Darko Djordjević, Senior OT technician, for their valuable assistance in considering data collection.

References

  1. Aydoğan S, Kaya N. The Assessment of the Risk of Unplanned Extubation in an Adult Intensive Care Unit. Dimens Crit Care Nurs. 2017; 36: 14-21.
  2. Chevron V, Ménard JF, Richard JC, Girault C, Leroy J, Bonmarchand G. Unplanned extubation: risk factors of development and predictive criteria for reintubation. Crit Care Med. 1998; 26: 1049-1053.
  3. Epstein SK, Nevins ML, Chung J. Effect of unplanned extubation on outcome of mechanical ventilation. Am J Respir Crit Care Med. 2000; 161: 1912-1916.
  4. Berkow L, Kanowitz A. Unplanned extubation in the perioperative environment. APSF Newsletter. 2022; 37: 14-16.
  5. Minda Z, Samuel H, Aweke S, Mekete G, Seid A, Eshetie D. Magnitude and associated factors of unplanned extubation in intensive care unit: A multi-center prospective observational study. Ann Med Surg (Lond). 2022; 79: 103936.
  6. Asai T. Airway management inside and outside operating rooms-circumstances are quite different. Br J Anaesth. 2018; 120: 207-209.
  7. McNett M, Kerber K. Unplanned Exubations in the ICU: Risk Factors and Strategies for Reducing Adverse Events. JCOM. 2015; 22(7): 303-311.
  8. Parotto M, Cooper RM, Behringer EC. Extubation of the Challenging or Difficult Airway. Curr Anesthesiol Rep. 2020; 10: 334-340.
  9. Sundaram S, Ramdas G, Paul AP, Krishnasamy SN. Accidental Perforation of Submental Flexometallic Tube. Anesth Essays Res. 2017; 11: 787-789.
  10. Cavallone LF, Vannucci A. Review article: Extubation of the difficult airway and extubation failure. Anesth Analg. 2013; 116: 368-383.
  11. Tailleur R, Bathory I, Dolci M, Frascarolo P, Kern C, Schoettker P. Endotracheal tube displacement during head and neck movements. Observational clinical trial. J Clin Anesth. 2016; 32: 54-58.
  12. Yan S, Zhang H. Impact of changes in head position during head and neck surgery on the depth of tracheal tube intubation in anesthetized children. BMC Anesthesiol. 2020; 20: 124.
  13. Joshi AA, Velecharla MS, Patel TS, Shah KD, Bradoo RA. Management of Difficult Laryngeal Exposure During Suspension Microlaryngoscopy. Indian J Otolaryngol Head Neck Surg. 2019; 71: 81-85.
  14. Calculator.net. BMI Calculator. Available at: https://www.calculator.net/bmi-calculator.html, date accessed: 20/12/2023.
  15. Bellhouse CP, Doré C. Criteria for estimating likelihood of difficulty of endotracheal intubation with the Macintosh laryngoscope. Anaesth Intensive Care. 1988; 16: 329-337.
  16. Mallampati SR, Gatt SP, Gugino LD, Desai SP, Waraksa B, Freiberger D, Liu PL. A clinical sign to predict difficult tracheal intubation: a prospective study. Can Anaesth Soc J. 1985; 32: 429-434.
  17. Savva D. Prediction of difficult tracheal intubation. Br J Anaesth. 1994; 73: 149-153.
  18. Kaplow R, Bookbinder M. A comparison of four endotracheal tube holders. Heart Lung. 1994; 23: 59-66.
  19. Thampi SM, Thomas S, Rai E. Intra-operative accidental extubation- An unexpected complication of the flexo-metallic tube. J Anaesthesiol Clin Pharmacol. 2018; 34: 414-415.
  20. Okano DR, Perez Toledo JA, Mitchell SA, Cartwright JF, Moore C, Boyer TJ. Intraoperative Accidental Extubation during Thyroidectomy in a Known Difficult-Airway Patient: An Adult Simulation Case for Anesthesiology Residents. Healthcare (Basel). 2022; 10: 2013.
  21. Ali QE, Amir SH, Kamal S, Bansal S. Management of accidental extubation during oral surgery by nasotracheal intubation using the King vision video laryngoscope and a gum elastic bougie – a case report. Rom J Anaesth Intensive Care. 2015; 22: 133-135.
  22. Gupta N, Bhalotra A, Gupta A, Bhadoria P, Garg R. Accidental Extubation in a Known Difficult Airway. J Anaesthesiol Clin Pharmacol. 2007; 23: 425-428.
  23. Garcha PS, Sreevastava DK, Singh SK. FLEXOMETALLIC ENDOTRACHEAL TUBE AND NASAL INTUBATION. Med J Armed Forces India. 2000; 56: 88.
  24. Tsukamoto M, Yamanaka H, Hitosugi T, Yokoyama T. Endotracheal Tube Migration Associated With Extension During Tracheotomy. Anesth Prog. 2020; 67: 3-8.