TITLE: Intubating condition, hemodynamic parameters and upper airway morbidity: A comparison of intubating laryngeal mask airway with standard direct laryngoscopy

  ABSTRACT.BACKGROUND:
Intubating Laryngeal Mask Airway (ILMA) is a relatively new device designed to have better intubating characteristics than the standard Laryngeal Mask Airway. This study was designed to compare Intubating Laryngeal Mask with standard Direct Laryngoscopy (DLS), taking into account ease of intubation, time taken for intubation, success rate of intubation, hemodynamic responses and upper airway morbidity.

ABSTRACT.MATERIALS AND METHODS:
Sixty patients, ASA I or II, of age between 20 and 60 years, were enrolled in this prospective and randomized study. They were randomly allocated to one of the two groups: group ILMA, Intubating Laryngeal Mask Airway; group DLS, Direct Laryngoscopy. The patients were intubated orally using either equipment after induction of general anesthesia.

ABSTRACT.RESULTS AND CONCLUSIONS:
DLS is comparatively a faster method to secure tracheal intubation than Intubating Laryngeal Mask. ILMA offers no advantage in attenuating the hemodynamic responses compared to direct laryngoscope. The success rate of intubation through Intubating Laryngeal Mask is comparable with that of DLS. The upper airway morbidity and mean oxygen saturation are comparable in both the groups.

BODY.INTRODUCTION:
Tracheal intubation is the gold standard for securing the airway for providing oxygenation and ventilation. Tracheal intubation using a laryngoscope inevitably alters the anatomy in order to bring the glottis in the line of sight. In addition, tracheal tube is designed for ease of intubation when the anatomy is thus altered and as a result its curvature does not always correspond with the contours of the relaxed anatomy of the upper airway.[1]  With the aim to create a new airway system with better intubation characteristics than laryngeal mask airway (LMA), Intubating Laryngeal Mask Airway (ILMA) was introduced by Dr. A. I. J. Brain in 1997. Other design goals were to eliminate the need for head and neck manipulation and insertion of fingers in the mouth during placement.[23]  The principal features of this system are an anatomically curved, rigid airway tube with an integrating handle, an epiglottis elevating bar, guiding ramp built into floor of mask aperture and silicone tracheal tube. The rigid bore tube permits the mask to be guided during endotracheal intubation and accommodates a normal sized tracheal tube. The tube curvature is specifically designed to fit into the palatopharyngeal arch, producing a firm seal. The guiding handle allows single-handed insertion, removal and positional adjustments during intubation. The epiglottic elevating bar replaces the three aperture bars of the standard LMA. It acts as an epiglottic ramp during insertion, keeps epiglottis from obstructing the airway, protects and elevates the epiglottis during tracheal tube passage. The wide, short tube offers less work of breathing and allows passage of larger instruments into the respiratory tract. The insertion technique is simpler and may be achieved by same rotational maneuver from any position that is useful when access is limited.[3]  This new device has been specially designed to aid blind and fiberscopic-guided tracheal intubation. Anatomically curved ILMA has overcome the limitation of Direct Laryngoscopy (DLS) also because it facilitates guidance of tracheal tube toward the glottis and does not need a line of sight from mouth to the glottis.[1]  The ILMA offers several advantages for difficult airway management also. The difficulty in viewing the larynx which underlies failed laryngoscopic intubation is probably irrelevant to ILMA placement and subsequent intubation. Currently no single test can assess the prediction of difficult intubation, therefore, difficult intubation will continue to occur in an unpredictable fashion. The priority remains to provide adequate training and equipment to manage unexpected failure. ILMA had been proved useful in cases of failed and difficult intubation.[4]  Moreover, ILMA-guided intubation may avoid or alleviate the mechanical stimuli to the oropharyngeal structures, which are inevitable while using a rigid DLS.[1] DLS to facilitate tracheal intubation produces marked pressor response. Although these changes are short lived, they may have detrimental effects on coronary and cerebral circulation of high risk patients.[5] This hemodynamic stress response to tracheal intubation can precipitate adverse cardiovascular events in patients with or without cardiovascular disease.  Laryngoscopic stimulation of oropharyngeal structures may be an important factor in the hemodynamic stress response associated with tracheal intubation. It has been suggested that distension of supraglottic tissues is the major cause of sympathoadrenal response to laryngoscopy. So, it may be that a technique of blind oral intubation produced significant reduction in stress response to intubation compared to DLS.[5] In principle, tracheal intubation techniques that avoid or minimize oropharyngeal stimulation might attenuate the hemodynamic stress response or reduce the incidence of airway morbidity.[6]  Joo and Rose[7] studied adult females with normal airways and showed that the hemodynamic stress response to blind and fiberoptic-guided intubation with ILMA was less than for laryngoscopic-guided intubation and that the incidence of postoperative pharyngolaryngeal morbidity, airway complications and overall intubation success rates were similar. However, another study by Kihara and associates[8] concluded that blind intubation through ILMA offers no advantages over the Macintosh laryngoscope for patients requiring intubation for elective surgery with normal airways, though it is a feasible alternative.  Hence, this study was designed to compare Intubating Laryngeal Mask with standard DLS, taking into account ease of intubation, time taken for intubation, success rate of intubation, hemodynamic responses and upper airway morbidity.

BODY.MATERIALS AND METHODS:
The present study was conducted after obtaining institutional approval, on patients admitted at Indira Gandhi Government General Hospital and Post Graduate Institute (IGGGH-PGI). Informed consent was obtained from each of the patients participating in the study. Sixty ASA I and II patients, of age 20–60 years, undergoing elective surgeries under general anesthesia were assessed prospectively. Patients at risk of gastric aspiration, pregnant patients, and obese patients were excluded from the study. Patients were randomly selected by sealed envelope technique to be studied under two groups.  Group ILMA: Intubating Laryngeal Mask Airway  Group DLS: Direct Laryngoscopy  On arrival into the anesthetic room, 18-G intravenous access was secured. All patients were premedicated with Diazepam 0.2 mg/kg oral, Inj. Ranitidine 50 mg IV, and Inj. Metoclopromide 10 mg IV. Automated non-invasive blood pressure monitor, pulse rate, oxygen saturation monitor, and electrocardiograph were connected. Baseline values were noted. Inj. Fentanyl 2 μg/kg was given 4 minutes before induction. Inj. Thiopentone 4 mg/kg, followed by Inj. Suxamethonium 1–2 mg/kg was used for induction and intubation.  In Group ILMA, ILMA of appropriate size (size 4 for men weighing more than 75 kg, size 3 for women and men weighing less than 75 kg) was selected. The insertion technique consisted of a one-handed rotational movement in the sagittal plane, with the head supported by the pillow. Specifically, the mask was fully deflated with the rim facing posteriorly. A bolus of water-soluble lubricant was applied posteriorly to the tip, which was then flattened against the palate with no attempt made to push the device inward until the saucer-shaped depression had been seen to be inverted against the palatal surface, drawing back slightly to ensure complete flattening of the rim into the dome of palate. The ILMA was then rotated inward, following the arc of the palate and the posterior pharyngeal wall, and the cuff was inflated with 20–30 ml of air (size 3: 20 ml; size 4: 30 ml). Successful placement–ventilatory ability was judged by the chest wall movement and capnography during manually assisted ventilation. If airway was not maintained, adjustment of ILMA as well as head was done. This was followed by insertion of lubricated 7.0, 7.5 or 8.0 mm PVC endotracheal tube through the metal tube of the ILMA gently without applying undue forces. If no resistance was felt, the cuff was inflated and circuit reconnected. Capnographic confirmation of the tracheal tube placement was sought. If resistance was felt or esophageal intubation occurred, a predetermined sequence of adjusting maneuvers was performed. Then, the ILMA was removed over the endotracheal tube and air entry with the endotracheal tube was reconfirmed. When tracheal intubation was not successful after three attempts, the patients were intubated with conventional laryngoscopy. In the Group DLS, Direct Laryngoscopy was done with Macintosh laryngoscope and intubation was done with a cuffed endotracheal tube of appropriate size with head and neck in neutral position. In both the study groups, maintenance of anesthesia was done with nitrous oxide and oxygen and halothane with pancuronium as muscle relaxant. At the end of the surgery, neuromuscular blockade was reversed with a mixture of atropine (0.02 mg/kg) and neostigmine (0.05 mg/kg) and extubation was done. Parameters studied were ease of intubation, time taken for intubation and hemodynamic parameters. Ease of intubation was assessed by recording the number of attempts required to intubate the patients' trachea and the degree of manipulation needed to achieve intubation. Time taken for intubation was assessed as follows. Group ILMA – Time between removal of face mask and ILMA insertion and time between disconnection of ILMA from the breathing system to successful tracheal intubation and ILMA removal. Group DLS – Time between removal of face mask and successful tracheal intubation. Hemodynamic parameters – Heart rate (HR) , systolic blood pressure (SBP), diastolic blood pressure (DBP) , mean blood pressure (MBP), oxygen saturation (SPO2). Upper airway morbidity: Sore throat, hoarseness, sore mouth, sore jaw/neck, swallowing difficulty. For intubation with each attempt of ILMA, one or more of the following methods were used as rescue measures:  
a)without movement of ILMA (neutral);b)pulling back of metal handle of ILMA toward intubator (extension) andc)pushing the handle of ILMA away from intubator (flexion).


BODY.RESULTS.AGE DISTRIBUTION:
The age group of the patients in the study was 18–60 years. The mean age in ILMA group was 32.23 years. The mean age in DLS group was 34.3 years. By applying independent samples test, the "P" value was found to be >0.05 and hence the two groups were comparable by mean age [Table 1].   Table 1 Distibution of age between the groups 

BODY.RESULTS.SEX DISTRIBUTION:
Out of 60 patients in the study, 17 were males and 43 were females. On applying the Students' "t" test, P value was >0.05 and hence the groups were comparable [Table 2].   Table 2 Distribution of gender between the two groups 

BODY.RESULTS.MALLAMPATTI CLASS DISTRIBUTION:
The distribution of patients into four Mallampatti classes is shown in Table 3. There was no statistical difference between the two groups as the P value was >0.05.   Table 3 Mallampatti class between the groups 

BODY.RESULTS.TYPE OF SURGERIES:
The patients who underwent elective surgeries under general anesthesia were included in this study. The various types of surgeries that were included in this study and their distribution among groups are shown in Table 4.   Table 4 Types of surgery between the groups 

BODY.RESULTS.EASE OF INTUBATION:
Tracheal intubation was successful in all the 30 (100%) patients in both ILMA and DLS groups. In DLS group, 27 (90%) patients were intubated in the first attempt, and 3 (10%) patients were intubated in the second attempt. In ILMA group, 25 (83.3%) patients were intubated in the first attempt. Four (13.3%) patients were intubated in the second attempt and one patient (3.3%) needed third attempt also.  Esophageal intubation occurred in five patients during the first attempt. Four of these patients were intubated successfully after applying adjusting maneuvers. One patient was intubated successfully after repositioning the ILMA (third attempt). Hence, the two groups were comparable with regard to ease of intubation [Table 5 and Figure 1].   Table 5 Ease of intubation between the groups   Figure 1Ease of intubation

BODY.RESULTS.TIME TAKEN FOR INTUBATION:
The mean time taken for ILMA intubation was found to be 63.66 seconds and for DLS group it was 21.63 seconds. Applying the Students' "t" test, the P value was found to be <0.05. Hence, it was concluded that the mean time taken for intubation through ILMA was statistically significant compared with that for DLS [Table 6 and Figure 2].   Table 6 Time taken for intubation between the groups   Figure 2Time taken for intubation

BODY.RESULTS.SUCCESS RATE OF INTUBATION:
The overall success rate was 100% in both the groups, that is, all the patients were intubated in both ILMA and DLS groups. But the first attempt success rate was 83.3% in the ILMA group, whereas it was 90% in the DLS group. Hence, this was comparable in both the groups [Table 7].   Table 7 Intubation success rate between the groups 

BODY.RESULTS.BASELINE HEMODYNAMIC VARIABLES:
Analysis of baseline hemodynamic parameters like SBP – 0, DBP – 0, MBP – 0 and HR – 0 was done. These baseline hemodynamic variables were found to be comparable between the two groups [Table 8].   Table 8 Baseline hemodynamics variables between the groups 

BODY.RESULTS.HEMODYNAMIC RESPONSE TO INTUBATION:
Hemodynamic responses to intubation were calculated by recording hemodynamic variables like HR and blood pressure during the following points:  Preinduction/after ILMA insertion (in the ILMA group)/immediately after intubation/1 minute after intubation/3 minutes/5 minutes/10 minutes after intubation.

BODY.RESULTS.HEMODYNAMIC RESPONSE TO INTUBATION.HEART RATE:
The mean HR in the group ILMA ranged from 79.70 to 86.50 and in group DLS it ranged from 79.13 to 87.17. The heart rates at various intervals are shown in [Table 9 and Figure 3].   Table 9 Change in heart rate at various time interval   Figure 3Heart rate

BODY.RESULTS.HEMODYNAMIC RESPONSE TO INTUBATION.BLOOD PRESSURE:
The SBP variation is as given in Table 10. The mean SBP variation ranged from 117.33 to 132.60 in the ILMA group, whereas it was from 115.80 to 131.90 in the DLS group. The P value was comparable in both the groups [Table 10 and Figure 4].   Table 10 Change in systolic arterial blood pressure at various time interval   Figure 4Systolic blood pressure  The mean DBP ranged from 76.63 to 87.37 in the ILMA group and 73.93 to 86.73 in the DLS group. There was no significant statistical difference between the two groups [Table 11 and Figure 5].  Table 11 Change in diastolic arterial blood pressure at various time interval   Figure 5Diastolic blood pressure  The MAP was measured during the above-mentioned timings and these values were tabulated [Table 12]. They ranged from 88.70 to 102.33 in the ILMA group and from 86.23 to 100.53 in the DLS group. By applying independent "t" test, P value was found to be 0.3799 [Table 12 and Figure 6].  Table 12 Change in Mean arterial blood pressure at various time interval   Figure 6Mean arterial blood pressure

BODY.RESULTS.HEMODYNAMIC RESPONSE TO INTUBATION.OXYGEN SATURATION:
The oxygen saturation ranged from 97% to 100% in both the groups. The saturation at different timings recorded is given in Table 13. Since both the comparative values are almost equal, the P value could not be calculated (it came as infinity). There was no statistical significance between the two groups with respect to oxygen saturation.   Table 13 Oxygen saturation at various time interval 

BODY.RESULTS.UPPER AIRWAY MORBIDITY:
The incidence of postoperative pharyngolaryngeal morbidity is given in Table 14. It was assessed by a 3-point scoring of five parameters after 2 and 24 hours in the postoperative period. In the table, the number of patients with points 1, 2, 3 are given in each group. T is the total number of patients with complications and the values in brackets represent the percentage of patients having that complication shown in Figure 7. P value of each complication has been calculated from the total number of patients having that particular complication (T) in Table 15.   Table 14 Postoperative upper airway morbidity (3-point scoring)   Figure 7Airway morbidity  Table 15 Postoperative upper airway morbidity (Incident) 

BODY.DISCUSSION:
Tracheal intubation is the gold standard for securing the airway and providing oxygenation and ventilation. The laryngeal mask represents a major advancement in airway management.[9] Relatively recently introduced ILMA overcomes the limitations of LMA. It acts as a ventilatory device and blind intubation guide.[3]  Laryngoscopic stimulation of oropharyngolaryngeal structures is an important factor in the hemodynamic stress response associated with tracheal intubation.[1011] The hemodynamic stress response to tracheal intubation can precipitate adverse cardiovascular events in patients with[12] and without[13] cardiovascular diseases. Intubating laryngeal mask offers a new approach for orotracheal intubation and is expected to produce less cardiovascular stress responses.[1] However, the reports available provide inconsistent results.  Thus, the purpose of this study was to compare ILMA with DLS, taking into account ease of intubation, time taken for intubation, success rate, hemodynamic responses and upper airway morbidity.  The ease of intubation was assessed by recording the number of attempts required to intubate trachea and the degree of manipulation needed to achieve intubation. Tracheal intubation in the first attempt was successful in 90% of patients in the DLS group and 83.3% patients in the ILMA group. Four patients in the ILMA group and three in DLS group were intubated in the second attempt. One patient in the ILMA group needed third attempt. The results were comparable in both the groups with regard to ease of intubation.  With ILMA, manipulation of the handle is directly transmitted to the inflatable cuff, altering its position in the airway. This is consistent with the study done by Kapila[14] in which alignment of the ILMA was assessed fiberoptically before intubation. Ease of intubation correlated with the view obtained and the degree of manipulation of the ILMA needed to achieve tracheal intubation. Our study results are comparable with those of this study.  Success rate was 100% in both the groups and hence were comparable. In previous studies, success rate of intubation through ILMA varied from 76 to 99.3%.[3810141516] However, in most studies, it varied from 93 to 97%; there was a potential difference at the first attempt, ranging from 56 to 87%. It is difficult to compare the studies due to inter-study differences in type of tracheal tube, anesthesia techniques, different size, selection criteria and sequences of adjusting maneuvers.[17] It has been suggested that adjusting the position of ILMA before intubation improves the success rate, but this remains unproven.[818] There are no studies comparing the different size selection and adjusting maneuvers. Our first attempt success rate (83.3%) is comparable with other studies.[819]  In our study, the mean time taken for intubation in the ILMA group was 63.66±14.10 seconds. The mean time taken for intubation in the DLS group was 21.63±3.61 seconds which is comparatively lesser than that of the ILMA. Our intubation time is comparable with that in other studies. This is because ILMA-guided intubation includes three steps: insert and confirm the position of ILMA, insert and confirm the position of endotracheal tube, then remove the ILMA. Thus, it is a time consuming procedure than using DLS for intubation. The longer time taken with ILMA can also be attributed to the lack of experience with the device compared with DLS.  Waltl[20] had done a similar study and compared the time taken for endotracheal intubation between ILMA and DLS groups. Our study results are comparable with their values. They concluded that in the absence of intubating difficulties, DLS is still the fastest method to secure endotracheal intubation.  One of the prominent advantages of ILMA-guided intubation is that it will not stimulate the base of the tongue, epiglottis and receptors in the pharyngeal mucosa mechanically. Therefore, theoretically, ILMA-guided intubation produces no adverse cardiovascular stress responses.  In our study, compared to the baseline, both the groups showed an increase in SBP, DBP, MBP and HR immediately after intubation and 1 minutes and 3 minutes after intubation. This variation was statistically insignificant between both the groups, which is consistent with the results of other studies.  Kihara and collegues[6] found that there were no significant differences in the hemodynamic variables like HR, SBP, DBP and MBP among the ILM and LS group. They stated that both ILM and Lightwand attenuate the hemodynamic stress response to tracheal intubation compared with laryngoscopy in hypertensive patients but not in normotensive patients. Since in our study we have chosen only normotensive patients, our study results are similar to their results.  Choyce and associates[5] measured the plasma catecholamine levels along with HR and blood pressure. They found that pressor response to intubation was of similar magnitude whether it was performed by DLS or blindly via an ILMA. Also, they stated that delayed removal of this device did not reduce the initial pressor response to intubation; instead this intervention was associated with a second significant pressor response.  Kihara and associates[21] investigated the impact of timing of removal of the ILMA on the magnitude of cardiovascular response. They found that if removal occurred within 1–2 minutes of insertion/intubation, the arterial pressure and HR increased to a greater extent than if the device is removed after 3 minutes. Since in our study removal of ILMA was done immediately after intubation, the responses were similar to that of DLS.  In the study of Joo and Rose,[7] MAP was higher in the patients receiving laryngoscopic orotracheal intubation than in those receiving ILMA-guided orotracheal intubation. Joo and Rose[7] did not apply the routine clinical practice because orotracheal intubation was performed 5 minutes after the insertion of ILMA in the study.  Zhang guo-hua and associates[1] showed that orotracheal intubations using ILMA and DLS under general anesthesia lead to similar pressor tachycardiac responses. There were no significant differences BP and HR at each time point. The results of our study are consistent with their results. Also, they have drawn out the reasons for their results as the following:  
ILMA-guided intubation, which includes three steps, is a time consuming procedure compared to the intubation using DLS. The long apnea and repeated airway manipulation may enhance hemodynamic responses.As compared with laryngoscopic intubation, ILMA-guided intubation may impose a greater pressure on the oropharyngeal structures and cervical vertebrae, which even exceeds capillary perfusion pressure of the pharyngeal structures, resulting in backward shifting of cervical vertebrae,[22] thus producing more stimuli to the local structures.In order to obtain an optimal position of the ILMA to facilitate insertion of tracheal tube, it is often required to move the ILMA back and forth, grasp and lift the jaw, adjust the patient's head and neck position and increase the volume of the cuff inflation or change the size of the ILMA. These auxiliary maneuvers may cause additional stimuli to the oropharyngeal structures.Before inserting tracheal tube into the trachea via the ILMA, the epiglottic elevating bar of the ILMA is lifted to elevate the epiglottis and approach the glottis, which results in stimulation of the epiglottis and periepiglottic structures. Previous work suggested that mechanical stimulus to the supralaryngeal area rich in nociceptive receptors can cause strong hemodynamic responses.ILMA-guided intubation is a blind procedure, so the tracheal tube is likely to be blocked by the downfolding epiglottis, anterior commissure, vocal cords and anterior tracheal wall. When tracheal tube is blocked, it is necessary to rotate the tracheal tube, move the ILMA up and down and adjust the patient's head and neck position, which may further stimulate the oropharyngeal structures. It may take longer time or even failure of tracheal intubation can occur by using ILMA.It has been shown that removal of ILMA after successful intubation is a more severe stimulus than insertion of the ILMA and endotracheal tube and can produce more severe hemodynamic responses because of stronger frictions.[23]In order to avoid accidental extubation, anesthetists often use stabilizing rod to further advance the tracheal tube, which may result in more frictions against tracheal wall and even stimulate the carina when the tracheal tube is inserted too deeply. It is demonstrated that tracheal stimulus is another main cause of hemodynamic responses to tracheal intubation.
  In our study, mean oxygen saturation was comparable at different timings in both the groups. There were no episodes of desaturation (<92%) in both the groups, emphasizing the fact that ILMA can maintain an airway and oxygenation of the patient throughout the intubation procedure, despite taking more time compared to DLS group. Kapila[14] showed that the salient feature of ILMA is the possibility of maintaining an airway and oxygenation of the patient throughout the intubation procedure.  We found no differences in pharyngolaryngeal complaints among both the groups. The data were less conflicting with those of Kihara and associates[8] and Joo and Rose,[7] reporting no difference between ILMA and DLS. We found that airway injury was more common with ILMA than with DLS. This may reflect genuine increase in injury, perhaps because of high mucosal pressures or easier detection of bleeding with the ILMA due to the cuff collecting supra-cuff material.[6] The incidence of sore throat and hoarseness was similar among the groups. For the ILMA group, there was no correlation between the intubation attempts and mucosal injury, sore throat or hoarseness. In our study, all the parameters were comparable except for swallowing difficulty which was statistically significant in the ILMA group. This may be due to the higher mucosal pressure of the ILMA cuff in the posterior pharyngeal wall.

BODY.CONCLUSIONS:

DLS is comparatively a faster method to secure tracheal intubation than Intubating Laryngeal Mask.Intubating Laryngeal Mask can maintain airway and oxygenation of the patient throughout the intubation procedure, despite taking more time than DLS.ILMA offers no advantage in attenuating the hemodynamic responses compared to DLS.The success rate of intubation through Intubating Laryngeal Mask is comparable with that of DLS.

Question: Compared to group DLS, Direct Laryngoscopy what was the result of group ILMA, Intubating Laryngeal Mask Airway on mean oxygen saturation?
Evidence: There was no statistical significance between the two groups with respect to oxygen saturation
Answer: no significant difference