A Comparative Study Of The Hemodynamic Response To Conventional Laryngoscopic Intubation And Intubation Through The Intubating Laryngeal Mask Airway
N B Murali, P V Kanna, Gunaseelan, A Hakkim
Citation
N B Murali, P V Kanna, Gunaseelan, A Hakkim. A Comparative Study Of The Hemodynamic Response To Conventional Laryngoscopic Intubation And Intubation Through The Intubating Laryngeal Mask Airway. The Internet Journal of Anesthesiology. 2013 Volume 32 Number 2.
Abstract
AIMS:
To compare the hemodynamic response to conventional laryngoscopic intubation and intubation through the ILMA in a prospective, randomized, controlled study (2) To compare the time taken for intubation in between the two groups (3) To compare the number of attempts required for successful intubation in both the groups (4) To compare the effect of time taken for intubation and the number of attempts on the hemodynamic variables measured.
MATERIALS AND METHODS:
The study was conducted at Chennai Medical College Hospital and Research Centre, Irungalur, Trichy . The hospital ethics committee approval was obtained. 120 patients of ASA grade I, II and III scheduled for elective surgery requiring endotracheal intubation were included in the study. Informed consent was obtained from all the patients enrolled. A thorough preoperative assessment was carried out. Mouth opening, neck movements and modified Mallampatti grading were assessed. Appropriate inclusion and exclusion criteria were used for selection of patients.
All the patients were randomly assigned into two groups each comprising of 60 patients. Computer generated random numbers were used for randomization of the study population. Group L patients were intubated with the conventional Macintosh laryngoscope and Group I patients were intubated through the ILMA
STATISTICAL ANALYSIS USED:
The statistical analysis of the obtained data was done using Chi-Square Test and Students -t test. A 'p value' < 0.05 was considered to be statistically significant
RESULTS:
In Group L all patients were successfully intubated and in the first attempt itself (100%). While in Group I, the overall rate of successful intubation was 93.32% and of which, 83.66% were intubated in the first attempt itself. In Group I, 6.66% of patients were intubated only in the second attempt. Another 6.66% patients could not be intubated even in the second attempt and therefore were excluded from the analysis of the hemodynamic variables. The mean intubation time in Group L (6.58±1.730 s) was shorter compared to Group I (51.14±2.178 s). This difference was statistically significant (p=0.000).The longer mean intubation time in Group I was due to the time taken for ILMA placement and intubation and also due to increase in the number of intubation attempts
The HR increased by 24% in Group L and by only 20% in Group I. In our study the SBP increased by 15.68% in Group L and only by 3.22% in Group I. The DBP increased by 26.79% in Group L and by 4.7% in Group I. These changes were present upto 3 minutes after intubation in Group L while there was a decreasing trend in Group I from the first minute onwards. The difference was statistically significant (p=0.000) up to 5 minutes after intubation. During intubation, the MAP increased by 20.71% in Group L and only by 2.67% in Group I. However, in Group I, the mean post intubation MAP was slightly higher than the baseline MAP. It started reducing from the first minute itself.
DISCUSSION:
In our study,in Group I, there was an overall decrease in hemodynamic response with respect to the SBP, DBP and MAP. Group I the HR, SBP, DBP and MAP responses were significantly less even during the second attempt. There was significant increase in the hemodynamic response within Group L when the time taken for intubation was more than the mean time. After intubation there was clinically significant increase in hemodynamic variables in Group L and very minimal response in Group I.
Though the mean intubation time and number of attempts in Group I was more than Group L, the hemodynamic response was very minimal. Whereas time taken for intubation did not alter the hemodynamic response in Group I.
Introduction
Discovery of endotracheal tube has made administration and maintenance of general anaesthesia easy and safe. Endotracheal tube placement is carried out under direct vision made possible by a laryngoscope. In order to bring the glottis into line of sight during laryngoscopy, there is distortion of the oropharyngeal structures. Such mechanical stimulation of respiratory tract enhances neuronal activity in the cervical sympathetic efferent fibers1, 2. This causes an increase in the heart rate3, blood pressure4 and constriction of blood vessels of skin and the coronary vasculature.
Although these responses are short lived they may be undesirable in patients with pre–existing myocardial and cerebral insufficiency. The sudden increase in the heart rate and blood pressure may cause left ventricular failure 5, myocardial ischemia5,6 and cerebral hemorrhage5. The incidence of these complications can be reduced by using alternative guiding devices like Intubating Laryngeal Mask Airway, Fiberoptic bronchoscope7 and Lightwand8.
Intubating Laryngeal Mask Airway(9) is a device that facilitates tracheal intubation without laryngoscopy. Anatomically curved Intubating Laryngeal Mask Airway facilitates guidance of the endotracheal tube towards the glottis. It has been suggested that Intubating Laryngeal Mask Airway guided intubation is less stimulating10,11,12 than laryngoscope guided intubation, as it avoids or alleviates the mechanical stimulation of the oropharyngeal structures. Other advantages like ease of insertion and its role in difficult airway makes it an alternative intubating device.
Subjects and Methods
The study was conducted at at Chennai Medical College Hospital and Research Centre, Irungalur, Trichy . The hospital ethics committee approval was obtained. 120 patients of ASA grade I, II and III scheduled for elective surgery requiring endotracheal intubation were included in the study. Informed consent was obtained from all the patients enrolled. A thorough preoperative assessment was carried out. Mouth opening, neck movements and modified Mallampatti grading were assessed. Following criteria were adopted for selection of patients.
Inclusion Criteria
Patients scheduled for elective surgery
Age 18 – 60 yrs
Weight 40 – 70 Kg
Both sex
ASA grade I, II and III
Mallampatti grade I and II
Exclusion Criteria
Age <18yrs >60yrs
Weight >70 Kg
ASA grade IV
History of gastro-esophageal reflex disease
Hypertensive patients
Cardio respiratory and cerebrovascular disease.
Mallampatti grade III and IV
Anticipated difficult intubation
All the patients were randomly assigned into two groups each comprising of 60 patients. Computer generated random numbers were used for randomization of the study population. Group L patients were intubated with the conventional Macintosh laryngoscope and Group I patients were intubated through the ILMA.
Premedication
All patients were fasted overnight and premedicated with Tablet Alprazolam 0.5mg and Tablet Ranitidine 150mg, 2hrs before surgery.
Procedure
After shifting the patient to the operating room, the following monitors were connected. – Noninvasive blood pressure, oxygen saturation and electro cardiogram. An 18G or 20G intravenous cannula was inserted and Ringer Lactate infusion was started. After a stabilization period of 5minutes, baseline values of HR, SBP, DBP and MAP were recorded.
Anaesthetic Technique
All the patients were preoxygenated for a period of 3mins with 100% oxygen. They were induced with Inj. Fentanyl citrate (2 mcg/kg) and Inj. Sodium Thiopentone (3–5 mg/kg) and the adequacy of ventilation was confirmed by the movement of chest wall. Inj. Vecuronium (0.1 mg/kg) was then given to facilitate endotracheal intubation. Patients were ventilated for a period of 3minutes with a mixture of 50% oxygen, 50% nitrous oxide and 1% Isoflurane. They were intubated as per the groups assigned.
In Group L, patients were intubated with size 3 Macintosh laryngoscope. External laryngeal manipulations were done to improve the glottic view in few cases. Female patients were intubated with poly vinyl chloride cuffed ETT of size 7.5mm internal diameter, while male patients were intubated with 8.5mm internal diameter ETT.
In Group I, intubation was done using ILMA size 3 and size 4 (as per the patient’s weight). In this group, after administration of vecuronium, ILMA was inserted by one handle rotation technique with the head and neck in neutral position. The ILMA cuff was inflated with air (as per the recommended volume). The position of ILMA was confirmed by adequacy of bag ventilation and chest wall movement. Once the position of ILMA was confirmed, intubation was attempted using lubricated, straight, cuffed, silicon tube of internal diameter 7.0mm and 7.5mm for ILMA size 3 and 4 respectively. The silicon tube was gently advanced through the ILMA. If there was no resistance, then the tube was advanced until intubation was accomplished. The ETT cuff was inflated with air (2 – 5 ml) and the anesthetic circuit was connected to the ETT. The position of the ETT was confirmed by ventilation, chest wall movement, auscultation of the chest and by capnograph. After confirming successful tracheal intubation, ILMA cuff was deflated and removed with the use of a calibrated endotracheal stabilizer rod. ILMA was rotated out of the oral cavity. If any resistance occurred while advancing the ETT through the ILMA, the ETT was withdrawn. The following adjustment maneuvers13,14 were applied in sequence before each additional intubation attempt:
Pulling the handle back towards the intubator (Extension Maneuver).
Withdrawal of the ILMA by 5 cm with the cuff inflated followed by re-insertion (Up-down Maneuver).
Adjusting the ILMA until the optimal seal is obtained (Optimization Maneuver).
Flexing the neck and extending the head (Head and Neck Maneuver).
Patients in whom intubation was not possible even after 3 attempts were considered as failure to intubate. Their hemodynamic variables were not included in the statistical analysis.
In both groups, after successful intubation ETT was connected to the anaesthetic breathing circuit and IPPV was established. Anaesthesia was maintained with a mixture of 50% oxygen, 50% nitrous oxide and 1% Isoflurane. The ventilator settings were adjusted to maintain an end tidal carbon-di oxide of 35 – 40mm of mg. During the study period Ringer lactate was infused at a constant rate of 15 ml/kg. No surgical stimulus was allowed during the study time.
Variables recorded:
The following variables were recorded.
HR, SBP, DBP, and MAP
Before induction
After induction
After intubation
1, 3 and 5 minutes after intubation.
Intubation time which was from the termination of manual ventilation using a facemask to restart of ventilation through ETT.
Number of attempts required for intubation.
Statistical analysis:
Statistical analysis was done using SPSS PC (17) version .Students-t test was used for analysis of quantitative variable and Chi-Square test for qualitative variables. p value < 0.05 was considered clinically significant.
Results
Following are the observations after this prospective study on ASA I ,II and III patients. A total of 120 adult patients were studied who were undergoing elective surgery under general anaesthesia in Chennai medical college hospital and research centre:
Age:
Table.1 shows the distribution of patients according to their age. Patients between 20 and 60 year of age were studied.
Table 1
2. Sex:
Table 2 shows the sex wise distribution of patients.
Table 2
3. Weight :
Table 3 shows the weight distribution of patients.
Table 3
4. Height:
Table 4 shows the height distribution of patients.
Table 4
5. ASA grade:
Table 5 shows the ASA grade distribution of patients.
Table 5
6. Mallampatti grade :
Table 6 shows the Mallampatti grade distribution of patients.
Table 6
Students-t test was used for analysis of age, weight and height between the two groups. There was no statistical significance in between the two groups.
Table 7
Chi-square test is used for analysis of sex distribution, ASA grade and Mallampatti grade in between Group L and Group I. There was no statistical difference in between Group L and Group I. Statistical analysis of mouth opening and neck mobility was not done as it was constant in all 120 patients.
Table 8
The above table represents the intubation data. It compares the time taken for intubation, number of attempts and overall rate of successful intubation between the two groups. In Group L all 60 patients were intubated in the first attempt. In Group I, 52 patients were intubated in the first attempt, 4 patients during the second attempt. 4 patients could not be intubated even after 3 attempts and therefore were excluded from statistical analysis.
Table 9
The mean preinduction HR was 76.43±9.361 in Group L while it was 76.20±8.005 in Group I. After intubation there was 24% increase in HR from the mean preinduction value in Group L while there was 20% increase in Group I. One minute after intubation, mean HR remained high by 14.22% in Group L and in Group I by 10.4%. Subsequently there was a decreasing trend in HR. At the end of 5 minutes the HR was 4.1% lesser than preinduction value in Group I and 1.32% in Group L.
Table 10
The above graph compares the change in mean HR in between Group L and Group I. The difference in the mean pre-induction HR was not statistically significant in between the two groups. After intubation, there was a significant difference which persisted upto 5 minute. The mean HR after intubation was statistically significant (p=0.018).
Graph 1
The mean pre-induction SBP was 122.33±7.147 in Group L and 124.14±5.072 in Group I. After intubation, mean SBP increased by 15.68% and 3.22 % from the mean preinduction value in Group L and Group I respectively. One minute after intubation mean SBP remained high by 6.55 % Group L and in Group I it reduced by 1.73% .There was a significant difference in mean SBP in between the two groups even after 3 and 5 minutes.
Table 11
The above graph compares the change in mean SBP in between Group L and Group I. There was no significant difference in between the two groups with respect to the mean pre-induction value. The mean SBP after intubation was statistically significant (p=0.000). This persisted up to 5 minutes after intubation.
Graph 2
The mean preinduction DBP was 71.32 ± 8.960 and 72.61 ± 7.363 in Group L and Group I respectively. After intubation, there was an increase in mean DBP by 26.79% and 4.7% from the mean preinduction value in Group L and Group I respectively. One minute later, in Group L, the mean DBP was 14.36 % higher than the mean preinduction value, while it reduced by 2.02% in Group I.
Table 12
The above graph compares the change in mean DBP in between Group L and Group I. The difference in the mean pre-induction DBP was not statistically significant in between the two groups. The mean DBP after intubation was statistically significant (p=0.000). This persisted upto 5 minutes after intubation.
Graph 3
The mean preinduction MAP was 88.90 ± 7.304 in Group L and 91.00 ± 6.663 in Group I. After intubation the mean MAP increased by 20.71% and 2.67 % from preinduction value in Group L and Group I respectively. One minute after intubation the mean MAP was increased by 10.21 % in Group L and in Group I it decreased by 3.25%. In Group L, it was higher than mean preinduction value until 5 minutes.
Table 13
The above graph compares the change in mean MAP in between Group L and Group I. There was no statistically significant difference in between the two groups with regards to the mean pre-induction MAP. The mean MAP after intubation was statistically significant (p=0.000). This persisted upto 5 minutes after intubation.
Graph 4
The above table and graph compares the time taken for intubation in between Group L and Group I. There was a statistically significant difference (p=0.000) in between the two groups.
Tables 15,16,17,18 and Graphs 6,7,8,9 compares the changes in the mean HR,SBP,DBP and MAP in Group L due to decrease (D) or increase(I) in the time taken for laryngoscopy and intubation from the mean time .
Table 14
The above table denotes the changes in the mean HR with regards to the mean time taken for intubation The mean preinduction HR in Group L (D) was 77.07 ± 9.493 and 74.82 ± 8.925in Group L (I). After intubation the mean HR was 92.12±8.157 in Group L (D) and 101.53 ± 7.641 Group L (I).
Graph 5
The above graph denotes the change in the mean HR with respect to mean time taken for intubation within Group L. The difference was statistically significant (p=0.000) from intubation upto 5 minutes after intubation.
Table 15
The above table denotes the changes in mean SBP with regards to mean time taken for intubation. The mean SBP at pre induction was 121.47 ± 7.317 in Group L (D) and 122.35 ± 8.344 in Group L (I). After intubation it was 136.93 ± 7.983 in Group L (D) and 153.12 ± 12.389 in Group L (I).
Graph 6
The above graph denotes the change in the mean SBP with respect to the mean time taken for intubation within Group L. There was statistically significant difference (p=0.000) within Group L after intubation. The difference persisted upto 5 minutes after intubation
Table 16
The above table represents the change in the mean DBP with respect to the mean time taken for intubation within Group L. The difference in the mean pre induction DBP within Group L was not statistically significant. After intubation the mean DBP was 87.88 ± 6.303 in Group L (D) and 96.88 ± 7.193 in Group L (I).
Graph 7
The above graph denotes the change in the mean DBP with respect to the mean time taken for intubation within Group L .The mean DBP had statistically significant difference within Group L after intubation which persisted up to 5 minutes after intubation.
Table 17
The above table represents the variations in the mean MAP in Group L with regards to the mean time taken for intubation. The mean pre induction MAP in Group L (D) was 87.63 ± 7.148 and 89.59 ± 8.596 in Group L (I). After intubation, it was 104.28±6.076 in Group L (D) and 115.0±8.617 Group L (I).
Graph 8
The above graph denotes the change in the mean MAP with respect to the mean time taken for intubation. The difference was statistically significant (p=0.000) from intubation up to 5 minutes after intubation.
Tables 19,20,21,22 Graphs 10,11,12,13 compares changes in mean HR,SBP,DBP and MAP in Group I due decreased (D) or increased(I) time taken for intubation using ILMA from the mean value.
Table 18
The above table represents the variations in the mean HR with regard to the mean time taken for intubation in Group I. The mean pre induction HR in Group I (D) was 77.69 ± 8.961 and 74.59 ± 6.629 in Group I (I) .After intubation the mean HR was 91.52±5.462 in Group I (D) and 91.30 ± 5.882 Group I (I).
Graph 9
The above graph represents the changes in the mean HR with respect to the mean time taken for intubation in Group I. The difference was not statistically significant (p=0.885) upto 5 minutes after intubation.
Table 19
The above table denotes the variations in mean SBP in Group I with respect to mean time taken for intubation. The mean SBP at pre induction was 127.66 ± 6.523 in Group I (D) and 125.56 ± 5.720 in Group I (I). After intubation it was 127.31± 6.665 in Group I (D) and 129.56 ± 6.704 in Group I (I).
Graph 10
The above graph represents the variation in the mean SBP with respect to the mean time taken for intubation in Group I. The difference was not statistically significant (p= 0.219) upto 5 minutes after intubation.
Table 20
The difference in the mean pre induction DBP within Group I was not statistically significant. After intubation, the mean DBP was 75.41± 6.697 in Group I (D) and 76.70 ± 7.834 in Group I (I). 5 minutes after intubation the mean DBP was 63.79 ± 6.641in Group I (D) and 59.04 ±10.158 in Group I (I).
{image:31}
The above graph represents the variation in the mean DBP with respect to the mean time taken for intubation in Group I. The difference was not statistically significant (p = 0.517) upto 5 minutes after intubation.
{image:32}
The mean MAP in Group I (D) was 93.00 ± 5.819 and 90.22 ± 6.079 in Group I (I). After intubation, it was 92.69 ± 6.054 in Group I (D) and 94.22 ± 6.222 Group I (I). 5 minutes after intubation the mean MAP was 77.86±6.306 in Group I (D) and 73.93±9.575 in Group I (I).
{image:33}
The above graph represents the variation in the mean MAP with respect to the mean time taken for intubation in Group I. The difference was not statistically significant (p = 0.354) within Group I up to 5 minutes after intubation.
{image:34}
The above table and graph compares the mean time taken for intubation in attempt 1 {Group I (1)} and attempt 2 {Group I (2)} in Group I. There was a statistically significant difference (p = 0.000) in the time taken between the two attempts.
Tables 27,28,29,30 and Graphs 21,22,23,24 compares the mean HR, SBP, DBP and MAP changes during attempt 1 and attempt 2 for intubation in Group I.
{image:35}
The mean pre induction HR in Group I (1) was 76.67 ± 8.109 and 70.00 ± 1.414 in Group I (I). After intubation the mean HR was 91.85±5.521 in Group I (1) and 96.75±3.775 Group I (2). One minute after intubation it was 84.37±5.736 in Group I (1) and 81.5 ± 2.38 in Group I (2)
{image:36}
The above graph denotes the change in the mean HR with respect to number of attempts required for intubation The difference was statistically significant after intubation (p = 0.035).One minute after intubation the difference was not statistically significant.
{image:37}
The above table denotes the change in the mean SBP with respect to number of attempts required for intubation. The mean pre induction SBP in Group I (1) was 126.65 ± 6.309 and 126.5 ± 5.066 in Group I (2). After intubation, it was 128.29 ± 6.728 in Group I (1) and129.75 ± 8.421 Group I (2).
{image:38}
The above graph denotes the change in the mean SBP with respect to number of attempts required for intubation. The number of attempts required for intubation altered the mean SBP within Group I. But the difference was not statistically significant (p =0 .682) even upto 5 minutes after intubation.
{image:39}
The mean pre induction DBP difference within Group I was not statistically significant. After intubation the mean DBP was 76.21 ± 7.534 in Group I (1) and 73.75 ± 4.5 in Group I (2). At the end of 5 minutes the mean DBP was 61.48 ± 9.087 in Group I (1) and 61.75 ± 2.754 in Group I (2)
{image:40}
The above graph represents the change in the mean DBP with respect to number of attempts required for intubation. The number of attempts required for intubation altered the mean DBP within Group I which was not statistically significant (p =0 .524) even upto 5 minutes after intubation.
{image:41}
The above table represents the change in the mean MAP with respect to number of attempts required for intubation. The mean pre induction MAP in Group I (1) was 91.71 ± 6.261and 91 ± 3.83 in Group I (2). After intubation, it was 93.5 ± 6.279 in Group I (1) and 92.5 ± 4.123 Group I (2).
{image:42}
The above graph represents the change in the mean MAP with respect to number of attempts required for intubation. The number of attempts required for intubation altered the mean MAP within Group I which was not statistically significant (p =0 .756) even up to 5 minutes after intubation.
Discussion
Laryngoscopy and tracheal intubation can cause significant hemodynamic response due to increased sympathetic activity. Even diagnostic laryngoscopy without intubation and tracheal suctioning are also associated with adverse circulatory changes15. Sympathetic stimulation could double the norepinephrine levels from 160 to 300 pg/ml and quadruple the epinephrine levels from 70 to 280 pg/ml16. This causes tachycardia, hypertension and dysrhythmias. During sympathetic stimulation of the heart, increase in HR and contractility occurs after a latent period of 3-5 seconds but returns to baseline values after 4-8mins. This delayed return to baseline values can be related to the slow rate of metabolism of norepinephrine in the cardiac tissue 17.This increase in serum catecholamine levels is responsible for most of the post synaptic effects on the cardiovascular system following laryngoscopy and intubation18.
Although these responses are short lived, they could be life threatening in patients with preexisting cardiovascular and cerebrovascular diseases. Age, drugs, depth of anaesthesia, hypoxia and hypercarbia are some of the confounding factors which influence the cardiovascular changes associated with laryngoscopy and intubation. Amongst many factors,the duration of laryngoscopy has also been found to be an important factor19 .These responses can lead to myocardial ischemia6, raised intra ocular5 and intracranial pressures. These responses can be attenuated by deepening the level of anaesthesia, administering drugs like opioids, beta blockers and lignocaine and the use of alternative airway devices like LMA, light wand and fiberoptic bronchoscope.
ILMA(9) is one such device which is used for ventilation and as a conduit for intubation. Very importantly, it does not stimulate the receptors in the hypopharynx. Therefore, theoretically, ILMA guided orotracheal intubation should cause lesser hemodynamic response than intubation using Macintosh laryngoscope. However, studies provide conflicting data on this issue. With this in mind, we planned a randomized, prospective, controlled study in 120 ASA grade I , II and III patients requiring general anaesthesia with endotracheal intubation who were scheduled for elective surgery. The patients were randomly allocated into two groups, 60 in each group. Group L patients were intubated with Macintosh laryngoscope while Group I were intubated through the ILMA. HR, SBP, DBP and MAP were recorded pre-induction, post induction, during intubation and at 1, 3, 5 minutes after intubation.
Both groups were similar with respect to the demographic profile, ASA grading and Mallampatti grading. In Group L all patients were successfully intubated and in the first attempt itself (100%). While in Group I, the overall rate of successful intubation was 93.32% and of which, 83.66% were intubated in the first attempt itself. In Group I, 6.66% of patients were intubated only in the second attempt. Another 6.66% patients could not be intubated even in the second attempt and therefore were excluded from the analysis of the hemodynamic variables. These findings are consistent with the study by Bharti et al20. In their study, 97.5% patients were successfully intubated through ILMA in the first attempt and of that, 10% were intubated in the second attempt. The study by Joo HS et al 21 also had similar findings .These studies show that the ILMA can be used as an alternative device for intubation.
The mean intubation time in Group L (6.58±1.730 s) was shorter compared to Group I (51.14±2.178 s). This difference was statistically significant (p=0.000).The longer mean intubation time in Group I was due to the time taken for ILMA placement and intubation and also due to increase in the number of intubation attempts. This is consistent with the study by Kihara et al22.They found that the mean intubation time using ILMA was 57 seconds and required more number of attempts as compared to laryngoscopic intubation.
On analysis of the HR, we found a statistically significant (p=0.018) increased response in Group L compared to Group I. The HR increased by 24% in Group L and by only 20% in Group I. The study by Evans et al23 also concluded that intubation through ILMA produced less response in the HR.
In our study the SBP increased by 15.68% in Group L and only by 3.22% in Group I. The DBP increased by 26.79% in Group L and by 4.7% in Group I. These changes were present upto 3 minutes after intubation in Group L while there was a decreasing trend in Group I from the first minute onwards. The difference was statistically significant (p=0.000) up to 5 minutes after intubation. Naveed et al 24 found a similar difference in the hemodynamic response to tracheal intubation using ILMA as compared to laryngoscopic intubation. They found 26% increase in the SBP and 23% in DBP in patients intubated with Macintosh laryngoscope as compared to only 8% increase in the SBP and 7% in DBP in patients intubated through the ILMA.
Like the SBP and DBP, MAP also had similar difference in between the two groups. During intubation, the MAP increased by 20.71% in Group L and only by 2.67% in Group I. However, in Group I, the mean post intubation MAP was slightly higher than the baseline MAP. It started reducing from the first minute itself. These data are consistent with the study by Joo et al 21 who found a significant increase in the MAP to intubation with conventional laryngoscopy as compared to intubation through ILMA.
In our study, there was an overall decrease in hemodynamic response with respect to the SBP, DBP and MAP. Bharti et al 20 also found a significantly lesser response during intubation in the SBP, DBP and MAP in the ILMA group compared to laryngoscopic group.
On further analysis of Group I the HR, SBP, DBP and MAP responses were significantly less even during the second attempt. This is similar to the findings by Kihara et al 25 who showed that increased number of attempts needed for intubation with ILMA produced very minimal or no difference in the hemodynamic variables measured.
The mean time taken for intubation in Group L was 6.58 ±1.730 s and in Group I was 51.14±2.178 s. There was significant increase in the hemodynamic response within Group L when the time taken for intubation was more than the mean time. Whereas time taken for intubation did not alter the hemodynamic response in Group I. This finding was similar to the study by Robert.K.Stoelting 19, where he demonstrated the influence of duration of laryngoscopy on the hemodynamic variables.
The reduced hemodynamic response in Group I as compared to Group L in our study was not seen in the study by Choyce et al 26 and Kihara et al 22. It is interesting to note that in both the above mentioned studies, opioids were not used for induction of anaesthesia. Omission of opioids in patients undergoing tracheal intubation does not reflect current clinical practice. Also, Kihara et al 33 did not use the manufacturer’s recommended soft tipped silicon ETT for intubation using ILMA. These could be the possible reason for the contradictory results in their studies.
Laryngoscopic stimulation of pharyngolaryngeal structures is an important factor which contributes for the hemodynamic response and the airway trauma associated with tracheal intubation. By using alternative guiding devices, such as ILMA, the incidence of these problems may be reduced as it facilitates tracheal intubation without laryngoscopy. Our study has revealed that the hemodynamic response associated with intubation using ILMA is less compared to conventional laryngoscopic intubation. Even though the number of attempts and time taken for intubation was longer in intubating using ILMA, the hemodynamic response was less.
{image:43}
SUMMARY
We conducted a randomized, prospective, controlled study to compare the hemodynamic response to conventional laryngoscopic intubation with intubation using ILMA. The study was done in 120 ASA grade I and II patients scheduled to undergo elective surgery under general anaesthesia with endotracheal intubation. The patients were randomly allocated into 2 groups by computer generated random numbers, 60 in each group. Group L patients were intubated using size 3 Macintosh laryngoscope with poly vinyl chloride, cuffed ETT. In Group I, patients were intubated using ILMA with straight, silicon tipped, cuffed ETT. All intubations were done by the same anaesthesia resident under supervision.
HR, SBP, DBP and MAP were recorded for both the groups during pre induction, post induction, intubation and at 1,3,5 minutes after intubation. Time taken for intubation and number of attempts were also recorded.
Statistical analysis was done using SPSS PC (17) version .Students-t test was used for analysis of quantitative variable and Chi-Square test for qualitative variables. p value < 0.05 was considered clinically significant.
There was no statistical difference in the demographic profile between the two groups. All patients in Group L were successfully intubated in the first attempt compared to 93.5% in Group I. The mean intubation time in Group I was longer than Group L. There was no statistical significance in the pre induction value of HR, SBP, DBP and MAP in both the groups. After intubation there was clinically significant increase in hemodynamic variables in Group L and very minimal response in Group I.
Though the mean intubation time and number of attempts in Group I was more than Group L, the hemodynamic response was very minimal.
CONCLUSION
We conclude that intubation through ILMA has lesser hemodynamic response compared to conventional laryngoscopic intubation. The hemodynamic response due to increased mean intubation time and number of attempts was very minimal with the use of ILMA. Hence it can be recommended in high risk patients requiring general anaesthesia with ETT to alleviate the hemodynamic response associated with laryngoscopic intubation.