Ann Thorac Surg 1997;63:768-772
© 1997 The Society of Thoracic Surgeons
Original Article: General Thoracic
The Laryngeal Mask Airway: A New Standard for Airway Evaluation in Thoracic Surgery
David Z. Ferson, MD,
Jonathan C. Nesbitt, MD,
Kimberly Kenfield Nesbitt, MD,
Garrett L. Walsh, MD,
Joe B. Putnam, Jr, MD,
David S. Schrump, MD,
Mary J. Johansen, PharmD,
Robert L. Jones, MD,
Jack A. Roth, MD
Departments of Anesthesia and Critical Care and Thoracic and Cardiovascular Surgery, The University of Texas M. D. Anderson Cancer Center, Houston, Texas
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Abstract
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Background. Thoracic surgeons typically perform fiberoptic bronchoscopy (FOB) before thoracotomy, usually on the day of the operation after intubation with a single-lumen endotracheal tube (ETT) and before insertion of a double-lumen ETT. This routine requires two laryngoscopies and two intubations. The laryngeal mask airway (LMA) is an airway device developed in England and approved by the Food and Drug Administration in 1991 for clinical use in the United States. It requires neither mask ventilation nor laryngoscopy and allows FOB visualization of the epiglottis, larynx, and entire trachea. We assessed the LMA as an alternative to a single-lumen ETT for FOB before thoracotomy.
Methods. Through prospective assessment, 50 patients underwent FOB after insertion of an LMA before thoracotomy. Pulse rate, blood pressure, ease of insertion of the LMA, quality of FOB, and complications of LMA insertion were assessed.
Results. During LMA insertion, blood pressure and pulse rate increased less than 5% from baseline in all patients. The LMA was inserted successfully in all patients within 10 seconds. No complications occurred as a result of LMA insertion.
Conclusions. Insertion of the LMA causes minimal hemodynamic response. From the time of induction of general anesthesia, insertion of the LMA is quick, simple, and safe and eliminates the need for endotracheal intubation with a single-lumen ETT before double-lumen tube insertion. The LMA, in contrast to the ETT, allows a complete survey of the larynx and trachea. The LMA is autoclavable, reusable, and cost effective. Therefore, in patients who require FOB immediately before thoracotomy, LMA use should be the standard for airway evaluation.
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Introduction
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See also page 772a.
Fiberoptic bronchoscopy (FOB) for direct visualization of the trachea and lower airways is usually performed before thoracotomy, after intubation with a single-lumen endotracheal tube (ETT). As a general rule, this is followed by insertion of a double-lumen tube for selective lung ventilation. Such a sequence requires two consecutive laryngoscopies and two tracheal intubations. The first intubation with a single-lumen ETT allows inspection of the lower airways, but it prevents examination of the epiglottis, glottis, and subglottic region.
Because of the field cancerization effect of cigarette smoke, there is a heightened risk of concurrent lung and upper aerodigestive cancers, with the highest association occurring between laryngeal and lung cancers [1, 2]. In one study, the reported incidence of a second primary lung cancer developing in patients with laryngeal cancer was 10.6% [3]. In light of such observations, it is important to examine the entire airway during FOB to rule out concurrent, asymptomatic malignant or premalignant disease.
In contrast, a novel airway device, the laryngeal mask airway (LMA) (Laryngeal Mask Co, Ltd, Oxon, England), was developed in the 1980s and approved by the United States Food and Drug Administration for clinical use in 1991 [4]. The LMA can be used in patients breathing spontaneously or for controlled ventilation. It does not require laryngoscopy for insertion and it is easy to place. We found the LMA to be an extremely useful adjunct in patients undergoing thoracotomy and sought to determine whether its use might preclude use of a single-lumen ETT for bronchoscopy before thoracotomy.
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Material and Methods
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From October 1995 to September 1996, 50 patients scheduled for elective thoracic surgical procedures were entered prospectively into our study. All patients required FOB before the surgical procedure, and there were no contraindications for LMA use. Systolic, diastolic, and mean arterial blood pressures and pulse were recorded; measurements for study were taken after the induction of general anesthesia. Mean arterial blood pressure and heart rate were determined 1 minute before and after insertion of the LMA. Intravenous induction was performed with propofol and nondepolarizing muscle relaxants. The primary opiate used was sufentanil. Anesthesia was maintained with inhalation agents, isoflurane in the majority of cases, or desflurane. A variable concentration of oxygen and air provided the fresh gas flow. Nitrous oxide was not used.
The recommended LMA insertion technique (Figs 1, 2
) imitates the swallowing mechanism. First, a fully deflated cuff was flattened against the hard palate. Then, the LMA was guided into the hypopharynx with the index finger of the dominant hand until a slight resistance was felt, as the tip of the mask encountered the upper esophageal sphincter. At this point, the LMA cuff was inflated with air to achieve an effective seal around the glottis. In all patients, the LMA was in place for a short time to complete the FOB.
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Fig 1. . With the left hand stabilizing the occiput, the posterior surface of the lubricated, deflated cuff is firmly applied against the hard palate as it is advanced into the pharynx. (Reprinted with permission from Brain A. The Intavent laryngeal mask instruction manual. 2nd ed. Henley-on-Thames, England: Intavent International SA, 1991.)
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Fig 2. . The cuff is pushed into the hypopharynx. Further gentle downward pressure on the shaft or proximal connector should ensure complete insertion. (Reprinted with permission from Brain A. The Intavent laryngeal mask instruction manual. 2nd ed. Henley-on-Thames, England: Intavent International SA, 1991.)
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The criteria used to assess the ease of LMA insertion were placement of the LMA within 10 seconds and the number of attempts needed to insert the device into the appropriate position. Differences in hemodynamic indices were calculated using the paired t test, with a hypothesized difference of zero.
No author has financial interest in the product, and the study was unfunded.
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Results
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The 29 men and 21 women had a median age of 59.6 years (range, 27 to 76 years). All patients except 1 had a diagnosed malignancy. Two patients had FOB alone; the remainder also underwent operations. All patients had an LMA inserted on the first attempt, in less than 10 seconds. Excellent position of the LMA was confirmed bronchoscopically in all patients (Figs 3, 4). No second primary tumors were seen, but vocal cord leukoplakia was identified in 2 patients. No complications occurred from the LMA. Linear regression analyses of pulse and mean arterial pressure are represented graphically in Figures 5 and 6; these indices showed minimal deviation from the line of identity. Paired t tests on the 50 patients showed no statistically significant differences in pulse and mean arterial pressure before or after LMA insertion (p > 0.05).
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Fig 3. . Endoscopic view of the glottic region with the laryngeal mask airway positioned, showing the bronchoscope exiting the shaft of the laryngeal mask airway. The epiglottis is seen in the upper part of the field.
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Fig 5. . Linear regression analysis of the pulse rate before and after laryngeal mask airway ( LMA) insertion. (bpm = beats per minute.)
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Fig 6. . Linear regression analysis of the mean arterial pressure ( MAP) before and after laryngeal mask airway (LMA) insertion.
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Comment
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The LMA was first developed in 1981 by a British anesthesiologist, Dr Archie Brain [4], and became commercially available in the United Kingdom in 1988. Since its introduction, there have been more than 20 million anesthetics delivered worldwide with use of the LMA [5]. The LMA is made of medical-grade silicone and can be used safely in patients with latex allergies. It is autoclavable and reusable, and it has been shown to be cost effective [6]. Each device costs approximately $200 and is guaranteed for at least 50 uses.
Combining the strengths of the noninvasive face mask and the invasive ETT, the LMA was created to fill an important functional gap that exists between the standard methods of airway management. As compared with the face mask, the LMA forms a low-pressure seal around the glottis, providing a good end to end connection between the artificial and the anatomic airway. In contrast to the ETT, the LMA does not penetrate the airway below the level of the glottis. Advantages of the LMA over the ETT include avoidance of laryngoscopy, less trauma to local tissues and vocal cords, and minimal effect on the cardiovascular response. The main limitation of LMA use remains the potential for aspiration. Although small, the overall incidence of aspiration related to non–LMA-delivered general anesthesia has been reported as 0.014% to 0.065% [7]. Published literature on the LMA suggests an overall risk of aspiration of approximately 0.02% [7]. In our study, the LMA was not used in any patient who was at risk for aspiration. No patient had evidence of aspiration, or pneumonia suspected to be a consequence of aspiration. Nasogastric suctioning was not performed in any patient before LMA insertion.
There are six different sizes of the LMA. The size 3 LMA is recommended for children and small adults weighing more than 30 kg. Size 4 is used in normal-size men and most women. The largest LMA, size 5, is reserved for large adults. If an air leak occurs after LMA cuff inflation, an inappropriately small size should be suspected, not an inadequate quantity of air in the mask cuff. In our series, inflation pressures were estimated by feeling the pilot balloon, but the recommended pressure should not exceed 60 cm H2O. If the esophagus is visualized at FOB, malpositioning has occurred from one of the following: (1) use of an LMA with inadequate size, (2) posterior folding of the LMA cuff within the pharynx, or (3) incomplete advancement of the tip of the LMA beyond the arytenoids, most commonly a consequence of incomplete cuff deflation before LMA insertion. In our group, the esophagus was never visualized.
In our study, all LMAs were placed successfully on the first attempt, within 10 seconds, even in those patients with anticipated or unanticipated difficult airways. The success rate for proper placement of the LMA is operator dependent. We achieved our high success rate because only two anesthesiologists (D.Z.F. and K.K.N.) were involved with every insertion in this series and both were familiar with the correct technique of insertion (as recommended by Brain [8]) and additional maneuvers (as described by Brimacombe and colleagues [9]). The LMA was used successfully in the management of 8 patients with difficult airways. There were 3 cases of unexpectedly difficult intubations during laryngoscopy for placement of the double-lumen tube. In 5 other cases of known difficult airways, the LMA was used as the initial step leading to placement of a double-lumen tube. In all of these cases, the LMA was essential for securing the airway and was used in accordance with the difficult-airway algorithm of the American Society of Anesthesiologists, established in 1993 [10] and reevaluated by Benumof in 1996 [11]. Our experience confirms that the LMA is extremely useful in both the anticipated and unanticipated difficult airway.
In 1944, Warren and Ehrenreich first reported a case of associated primary laryngeal and lung malignancies [12]. Since then, the association between lung cancer and upper aerodigestive malignancies has been well established [1–3]. Strigenz and associates [3] studied 790 patients with upper aerodigestive tract cancer over a 10-year period. Their findings revealed an increased incidence of additional primary lung tumors; primary lung malignancies developed in 5.6% of all patients. Furthermore, the strongest correlation—10.6%—was found between index primary laryngeal lesions and the ultimate development of a second primary lung lesion. Similar findings have been noted by others [1]. For example, Yellin and co-workers [1] found that in their 1,450 patients with upper airway cancer, the incidence of lung cancer was 4.1%; lung cancer was the most common additional second primary tumor. However, the incidence of a second primary upper airway cancer occurring after a lung cancer was less than 1%. A study by the Lung Cancer Study Group found that in 2.6% of patients who survived more than 5 years after resection of their early-stage (T1N0) non–small cell lung cancers, malignancies developed in the nasopharynx, larynx, or trachea [13]; meanwhile, lung cancer recurrence in these patients decreased with time in proportion to the number of new aerodigestive epithelial cancers.
The thoracic surgeon's responsibility to the patient includes both the operation and assessment of the status of the airway. Typically, the patient who presents with lung cancer undergoes bronchoscopy before thoracotomy by the pneumologist or the referring physician. The surgeon must assess both the tracheobronchial anatomy and its relation to the primary disease. Bronchoscopy and thoracotomy during the same anesthesia is safe and efficient. Fiberoptic bronchoscopy through the ETT provides access to the distal trachea and beyond, yet precludes complete visualization of the upper airway. After FOB, a second direct laryngoscopy is required for insertion of a double-lumen tube for selective lung ventilation.
Because of the association between lung and aerodigestive malignancies, comprehensive evaluation of the airway is critical and should include inspection of the supraglottic, aryepiglottic, glottic, and infraglottic regions, which are not commonly seen using traditional practices involving a single-lumen ETT. By using the LMA, the surgeon can view these structures without ETT obstruction, while maintaining a consistent and reliable means of ventilation. In our group of patients, no second primary cancers were seen. Vocal cord leukoplakia, however, was found in 2 of the 45 patients with lung cancer (4.4%). These lesions would not have been identified if FOB had been performed in the conventional fashion through a single-lumen ETT. With continued use of the LMA as described, we may continue to identify unexpected pathologic processes.
Use of the LMA also circumvents the hemodynamic problems associated with direct laryngoscopy and intubation. The latter methods have been associated with catecholamine stimulation and hemodynamic changes that result in undesirable heart rate and blood pressure elevations [14]. Moreover, the increase in hemodynamic response seen with laryngoscopy may be especially harmful in patients with cardiovascular and cerebrovascular disease. In light of these problems, Braude and associates [15] compared hemodynamic changes in two groups of patients after LMA placement or ETT insertion. After standard thiopental anesthetic induction, both groups demonstrated a transient rise in systolic and diastolic blood pressures. The responses in the LMA group, however, were attenuated and shorter. A subsequent study showed that heart rate was elevated longer in patients who were intubated endotracheally than in those who underwent LMA placement [16]. In our study, there was no significant change in hemodynamic indices after LMA insertion, a finding that further substantiates that the LMA is a well-tolerated device. Although not yet explained, this observed low rate of hemodynamic response to the LMA may be related to a lack of direct laryngeal or tracheal stimulation, to minimal stimulation of the pharynx, or to a short duration of direct airway stimulation [17].
After induction of general anesthesia, insertion of the LMA is quick, simple, and safe and causes minimal changes in hemodynamic indices. For patients requiring FOB before thoracotomy, the LMA eliminates the need for endotracheal intubation with a single-lumen ETT before double-lumen tube insertion. In contrast to the ETT, the LMA provides access for a complete survey of the larynx and trachea. In addition, the LMA is autoclavable, reusable, and cost effective. Therefore, in patients requiring FOB immediately before thoracotomy, LMA use should be the standard for airway evaluation.
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Footnotes
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Presented at the Forty-third Annual Meeting of the Southern Thoracic Surgical Association, Cancun, Mexico, November 7–9, 1996.
Address reprint requests to Dr Nesbitt, Department of Thoracic and Cardiovascular Surgery, The University of Texas M. D. Anderson Cancer Center, Box 109, 1515 Holcombe Blvd, Houston, TX 77030.
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References
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- Minna JD, Pass H, Glatstein E, et al. Cancer of the lung. In: DeVita VT, Hellman S, Rosenberg SA, eds. Cancer: principles & practice of oncology. Philadelphia: Lippincott, 1989:594.
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Abstract
Introduction
