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Laryngoscopic Evaluation Essay

Endotracheal intubation using the C-MAC® video laryngoscope or the Macintosh laryngoscope: A prospective, comparative study in the ICU

Crit Care. 2012; 16(3): R103.

Published online 2012 Jun 13. doi:  10.1186/cc11384

This article has been cited by other articles in PMC.

Abstract

Introduction

Endotracheal intubation in the ICU is a challenging procedure and is frequently associated with life-threatening complications. The aim of this study was to investigate the effect of the C-MAC® video laryngoscope on laryngeal view and intubation success compared with direct laryngoscopy.

Methods

In a single-center, prospective, comparative before-after study in an anesthetist-lead surgical ICU of a tertiary university hospital, predictors of potentially difficult tracheal intubation, number of intubation attempts, success rate and glottic view were evaluated during a 2-year study period (first year, Macintosh laryngoscopy (ML); second year, C-MAC®).

Results

A total of 274 critically ill patients requiring endotracheal intubation were included; 113 intubations using ML and 117 intubations using the C-MAC® were assessed. In patients with at least one predictor for difficult intubation, the C-MAC® resulted in more successful intubations on first attempt compared with ML (34/43, 79% vs. 21/38, 55%; P = 0.03). The visualization of the glottis with ML using Cormack and Lehane (C&L) grading was more frequently rated as difficult (20%, C&L grade 3 and 4) compared with the C-MAC® (7%, C&L grade 3 and 4) (P < 0.0001).

Conclusion

Use of the C-MAC® video laryngoscope improved laryngeal imaging and improved the intubating success rate on the first attempt in patients with predictors for difficult intubation in the ICU setting. Video laryngoscopy seems to be a useful tool in the ICU where potentially difficult endotracheal intubations regularly occur.

Introduction

Airway management for critically ill patients in locations other than the operating room is challenging and frequently associated with life-threatening complications. For example, the incidence of difficult endotracheal intubations is higher in the ICU than in the operating room. The number of difficult intubations ranges from 10 to 22% in critically ill patients [1-3]. Visualizing the glottis is often difficult in the ICU due to the constraints of space, the position of the patient and the accompanying comorbidities [4]. Additionally, multiple attempts of endotracheal intubation are often necessary to secure the patient's airway in the ICU setting and are known to increase the risk of life-threatening complications, such as severe hypoxia, esophageal intubation, aspiration and cardiac arrest [2,5,6]. This knowledge suggests that optimization of visualization of the glottis might reduce complications.

Video laryngoscopes seem promising for airway management [7]. Video laryngoscopes contain a small camera and a light source at the distal third of the blade. The video picture is transferred to a monitor. The C-MAC® video laryngoscope (Karl Storz GmbH & Co. KG, Tuttlingen Germany) evaluated in this study uses Macintosh-shaped blades. Two approaches to visualize the glottis with the use of a Macintosh video laryngoscope blade are available: first, the direct view of the glottis; and second, an indirect view by means of a miniature camera on the screen of the monitoring unit. Several studies have shown the successful use of the C-MAC® in the operating room and in prehospital emergency medicine [8,9]. The use of Macintosh blades with the C-MAC® improved the glottic view in patients who were difficult to intubate using direct laryngoscopy in the operating room [10]. These data cannot be directly translated to the situation on the ICU, because performing endotracheal intubation is more challenging in this environment.

The aim of this study was to evaluate the glottic view, number of intubation attempts and success rate of endotracheal intubation in an anesthetist-lead surgical ICU using Macintosh laryngoscopy (ML) or the C-MAC® video laryngoscope. Additionally, we evaluated whether the level of physician experience might influence visualization of the glottis or intubation success. We hypothesized that the use of a video laryngoscope would improve the glottic view and reduce the number of intubation attempts.

Materials and methods

The ethical committee of the medical association of the State of Rhineland-Palatinate approved the study and the committee waived the need for specific written informed consent. The study was performed in a 21-bed anesthetist-lead adult surgical ICU of a tertiary-care university teaching hospital.

This prospective, comparative, before-after study evaluated the endotracheal intubations of critically ill patients over a 2-year period in the ICU. Participating physicians completed a standardized evaluation form immediately after performing an endotracheal intubation.

Predictors of potentially difficult tracheal intubation were recorded for each patient on the standardized evaluation form: short neck with large circumference, obesity, limited mouth opening (< 3 cm), limited neck movement, presence of a large tongue and a short thyromental distance.

The laryngoscopic view was evaluated using the Cormack & Lehane (C&L) classification scale [11] and the Percentage of Glottic Opening scale (POGO) [12]. The number of intubation attempts, intubation success, the indication for the intubation and possible complications were documented. The lowest oxygen saturation during intubation was measured using pulse oximetry. Age, gender, physical status, the Simplified Acute Physiology Score and the Sequential Organ Failure Assessment II score were collected for all patients in this study at admission into the ICU. The clinical experience of the laryngoscopist was also noted. Junior physician was defined with up to 3 years clinical experience, senior physician with more than 3 years of training, and specialists were board-certified anesthesiologists.

Over a 12-month evaluation period (January 2009 to January 2010), the standard procedures for tracheal intubation remained unchanged. Restrictions concerning the selection of airway management tools for endotracheal intubation did not exist (baseline). Direct laryngoscopy (ML) was performed using a size 3 or size 4 regular Macintosh blade. Alternative airway devices (for example, intubation endoscope, laryngeal mask airway, and cricothyrotomy set) were always available in an airway cart at the bedside. After three failed attempts at endotracheal intubation, alternative devices (for example, endoscopic intubation) were used according to the in-house difficult airway algorithm.

The presence of at least two healthcare professionals, with at least one senior physician, was standard for all intubations. If possible, pre-oxygenation for 3 minutes at a high constant flow or non-invasive positive-pressure ventilation was administered to the patients. The medication for the induction of anesthesia was sufentanil (0.3 to 1.0 μg/kg) in every patient, with either propofol (1.5 to 2.0 mg/kg), ketamine (1.5 to 3 mg/kg) or etomidate (0.2 to 0.3 mg/kg). Rocuronium (0.4 to 0.9 mg/kg) was always used for neuromuscular blockade. In cardiac arrest patients, intubations were performed without medication. A malleable stylet in a hockey-stick shape was always used for tube placement. If visualization of the glottis or the placement of the endotracheal tube was difficult, the manipulation of the larynx was performed according to the instructions of the laryngoscopist. The successful placement of the endotracheal tube was confirmed using capnography.

We then evaluated endotracheal intubations over a second 12-month period (February 2010 to February 2011) after implementing two C-MAC® video laryngoscopes (Karl Storz GmbH & Co. KG) in the ICU (intervention phase). Video laryngoscopy was performed using the Karl Storz Macintosh shaped blades for C-MAC® size 3 or size 4 (Figure ​1). ICU physicians were given didactic instruction on the proper use of the C-MAC® along with training on manikins. The ICU staff were advised to perform endotracheal intubations using the C-MAC® instead of ML when appropriate. The procedures for intubation, the medication for anesthesia and the in-house difficult airway algorithm were identical to the first evaluation period. Documentation was identical to the previous study period of 2009 to 2010.

Figure 1

The C-MAC® video laryngoscope with size 3 and size 4 blades.

Patients who presented with predictors of potentially difficult tracheal intubations were identified and analyzed in a subgroup for first-attempt intubation success and visualization of the glottis.

After use, the C-MAC® blades and cable with the electronic module were manually cleaned and immersed in a cleaning solution (Teralin®; Schülke & Mayr, Norderstedt, Germany). Automated processing using an endoscope cleaning and disinfection unit was then used for disinfection (BHT 2000®; BHT Hygiene Technik, Gersthofen, Germany). The monitor unit was cleaned manually using disinfection cloths (Mikrobac®; Bode, Hamburg, Germany).

Data were analyzed using GraphPad Prism (version 5a for MAC; GraphPad Software, San Diego, CA, USA). Data are expressed as the mean ± standard deviation and the median (interquartile range) for non-Gaussian variables. The comparison of the two proportions was performed with the use of the chi-square test or Fischer's exact test when appropriate. The comparison of means was performed using Student's t test, and comparison of the medians was performed with the Mann-Whitney test. One-way analysis of variance with Dunn's post-hoc test was used for multiple comparisons. The differences were considered statistically significant if P < 0.05.

Results

A total of 274 patients were evaluated during the 2-year study period (Figure ​2). There were no differences in their demographic variables (Table ​1). Physical status was similar between groups (Simplified Acute Physiology Score); however, patients in the ML group presented with a higher Sequential Organ Failure Assessment II score (P < 0.05; Table ​1). The indications for intubation did not differ between the ML and the C-MAC® groups (Table ​1).

Figure 2

Flow chart of the prospective study. ML, Macintosh laryngoscopy.

Table 1

Demographic data, indication for endotracheal intubation, and level of laryngoscopist training during baseline and intervention

With the availability of the video laryngoscope, more physicians-in-training performed endotracheal intubations. In contrast, mainly specialists performed endotracheal intubations during the baseline phase (P < 0.001; Table ​1).

During the baseline phase of the study, a total of 113 intubations were performed using ML. A total of 117 intubations were performed using the C-MAC® during the intervention phase of the study. After the introduction of a video laryngoscope, the use of intubating endoscopy was used less frequently used for intubation compared with the baseline phase (5/134, 4% vs. 18/140, 13%; P < 0.05) (Figure ​2).

After introduction of the C-MAC®, eight patients were intubated using ML. Five patients were intubated in one attempt, and three patients were intubated after two attempts. There were no differences in the number of intubation attempts, successful intubations and views of the glottis between junior, senior and specialist physicians (Table ​2).

Table 2

Intubation attempts and visualization of the glottis using the Cormack & Lehane grade

No differences in predictors for potential difficult intubation were observed (Table ​3). In 15% of ML and 18% of C-MAC® intubations, at least one predictor existed. The most often described predictor was a short neck with large circumference (Table ​3).

Table 3

Predictors for difficult intubation, number of complications and lowest documented oxygen saturation during endotracheal intubation

Complications during endotracheal intubations occurred in 17 (12%) cases in the baseline phase of the study and in 14 (10%) patients after the C-MAC® was introduced in the intervention phase of the study (P = 0.7; Table ​3). The types of complications did not differ between the groups. The oxygenation saturation as measured by pulse oximetry did not differ between groups (Table ​3).

The number of attempts needed for securing the airway of patients was not different between the ML and the C-MAC® groups (P = 0.21; Figure ​2). The rate for difficult intubation (using the definition of at least two failed intubation attempts) was 7% and 3% in the ML and C-MAC® groups, respectively (Figure ​2). The rate of success for the first intubation attempt did not differ when the C-MAC® was used compared with ML (103/117, 88% vs. 89/113, 79%; P = 0.08). If at least one predictor for potential difficult intubation was present, the success rate for endotracheal intubation at the first attempt was higher (34, 79%) in the C-MAC® group compared with the ML group (22, 56%; P = 0.03) (Table ​4).

Table 4

Patients presenting with at least one potential predictor for difficult intubation

Using the C&L grading scale, the visualization of the glottis with ML was more frequently rated as difficult (Figure ​2). The glottis could not be visualized in 23 patients (20%, C&L grade 3 or 4), was only partially visualized in 37 patients (33%, C&L grade 2) and was fully visualized in 53 patients (47%, C&L grade 1) (Figure ​3). In contrast, visualization of the glottis was improved with the C-MAC® (P < 0.0001): C&L grade 3 or 4 was rated in eight patients (7%), C&L grade 2 was rated in 24 patients (21%) and C&L grade 1 was rated in 85 patients (73%). The use of the C-MAC® resulted in an improved view of the glottis as measured by the POGO scale compared with ML (60 ± 36% vs. 82 ± 25%; P < 0.001). The glottic view was improved using the C-MAC® compared with ML when predictors for difficult intubation were present (C&L, P = 0.027; POGO, P < 0.001) (Table ​4).

Figure 3

Visualization of the glottis using Cormack & Lehane classification. ML, Macintosh laryngoscopy. P < 0.0001.

Discussion

In this prospective study of 247 consecutive patients over a 2-year period, endotracheal intubation was associated with a high rate of difficult laryngeal visualization and a high number of repeated intubation attempts. The use of the C-MAC® video laryngoscope improved visualization of the glottis during airway management in the ICU. Patients with a potential difficult airway had a higher success rate for intubation at the first attempt when the video laryngoscope was used.

The major advantage of video laryngoscopes is that the glottis can be visualized indirectly via a screen without a direct line of view (look around the corner). One potential problem is that the tip of the endotracheal tube has to pass a sharp angle to enter the larynx, which increases the risk of contact with the anterior tracheal wall. As a result, the tube cannot be easily advanced into the trachea. This phenomenon has been described with the use of several video laryngoscopes, such as the McGrath Series 5® (Aircraft Medical Ltd, Edinburgh, UK) and the GlideScope® (Verathon Inc., Bothell, WA, USA). The use of a video laryngoscope with a Macintosh shaped video blade reduced the problem of tube advancement despite a good glottic view compared with the video laryngoscopes that use a more curved blade. In a comparison of the use of ML versus the use of the C-MAC® in groups of patients who had a difficult laryngoscopy during a scheduled surgical procedure, the use of the C-MAC® improved the glottic view in 94% (49/52) of patients [10]. In the operating room, use of the C-MAC® in patients with a predicted difficult airway improved optical access to the glottis compared with direct laryngoscopy using a Macintosh laryngoscope and resulted in more successful intubations at the first attempt [13].

Little is known about the effect of using a video laryngoscope in the challenging ICU environment. In a small study examining the effect of the GlideScope® video laryngoscope, no effect was observed on the number of intubation attempts and the occurrence of complications [14]. In the emergency department, no difference in intubation success between the GlideScope® and direct laryngoscopy was described [15]. In the presence of a difficult airway situation, however, use of the video laryngoscope resulted in a higher success rate compared with direct laryngoscopy [15]. Despite numerous promising studies, not all instruments using indirect laryngoscopy were found to be efficient in settings outside the operating room. In a prehospital randomized study, the use of the Airtraq® laryngoscope (Podol Lt., Vizcaya, Spain) was associated was a high incidence of failed intubations compared with direct laryngoscopy using a Macintosh laryngoscope [16]. In our study, the use of the C-MAC® only resulted in a more successful intubation at the first attempt in predicted difficult airways, compared with the use of ML. The overall success rate of the C-MAC® was similar to ML when all endotracheal intubations were analyzed.

After the introduction of the C-MAC®, specialist anesthesiologists less frequently performed endotracheal intubation personally. However, this had no effect on the glottic view, the number of intubation attempts and the number of complications.

Difficult intubation is a rather common event in locations other than the operating room. Recent studies have stated that the occurrence of difficult intubations in critically ill patients ranges from 10 to 22% [1-3]. In our study, the rate of difficult laryngoscopy (C&L grade 3 and 4) using ML was 20%. This is remarkable since the large majority of physicians participating in this study were anesthesiologists. A French study reported a similar incidence of difficult laryngoscopy [3]. The incidence of difficult laryngoscopies reported for the operating room (5%) is significantly less frequent than in other settings [17]. In a recent report from the UK, more than 60% of the events associated with airway management in the ICU led to death or brain damage [18]. The corresponding incidence in the operating room was 14% [19]. The possible reasons for the high rate of severe complications outside the operating room are probably patient-related factors and include multiple organ failure, advanced age, the use of vasopressors and low fluid responsiveness [1].

Limitations

The major limitation of this work is that a nonrandomized study design was used. This might have resulted in a higher Sequential Organ Failure Assessment II score in the ML group and heterogeneity of the training level of the laryngoscopists. We decided on a before-after design because we did not have the resources to guarantee patient randomization throughout the 2-year study period in our multiple-floor ICU. This study was planned in 2008, when few data were available about performance of video laryngoscopes in patients. This manuscript gives a very good background for future study designs, sample calculations, and so forth. More than 400 patients probably need to be included in a future study to show the effects on intubation success for the whole ICU population. Another possible limitation of this study was the subjective nature of the assessment of the laryngeal view completed by the participating physicians using the C&L grading system and the POGO score. The reproducibility of laryngeal view grading in anesthesiologists familiar with this classification is limited [20]. Evaluated data are self-reported, so a recall or reporting bias might be present.

Most of the studies that analyze advanced airway management tools are conducted by experienced operators, which could lead to a bias in favor of the choice of the instrument analyzed. Our study was conducted in a real-life setting, and the participating physicians represented a typical range of anesthesiologists.

Conclusions

With the presence of at least one predictor for difficult intubation, a high incidence of an insufficient glottic view and repeated intubation attempts during airway management was documented in the ICU. The introduction of the C-MAC® video laryngoscope improved the laryngeal view during intubation. In patients with the presence of a predicted difficult airway, use of the C-MAC® resulted in more successful intubations on the first attempt. C-MAC® video laryngoscopy using a Macintosh shaped blade seems to be a useful technique as the initial approach for endotracheal intubation in the ICU. These data justify larger randomized studies to evaluate the impact of video laryngoscopy on patient outcome.

Key messages

• In this study, 15 to 18% of patients presented with at least one predictor for difficult intubation.

• Difficult visualization of the vocal cords using direct ML is common during endotracheal intubation in the ICU.

• Use of the C-MAC® video laryngoscope improved visualization during endotracheal intubation.

• Using the C-MAC® video laryngoscope for intubation reduced the number of intubating attempts if at least one predictor for difficult intubation was present.

Abbreviations

C&L: Cormack & Lehane grading; ML: Macintosh laryngoscopy; POGO: percentage of glottis opening.

Competing interests

Neither the Department of Anesthesiology of the University Medical Centre of the Johannes Gutenberg University-Mainz, Germany or any of its employees received any compensation for this work. Airway Hands-on Workshops and studies of the Department of Anesthesiology have been supported by Aircraft Medical Ltd (Edinburgh, UK), Ambu GmbH (Bad Nauheim, Germany), Karl Storz GmbH & Co. KG (Tuttlingen, Germany), The Surgical Company GmbH (Kleve, Germany) and Verathon Medical (Rennerod, Germany). No other funding or competing interests declared. The authors alone are responsible for the content and writing of the paper.

Authors' contributions

RRN participated in the study design, data analysis, interpretation of the data and writing of the manuscript. SG and NE participated in the study design, and performed data acquisition and data analysis. MD participated in the study design and revised the manuscript. TP participated in the study design, data analysis and interpretation of the data, and revised the manuscript. All authors read and approved the manuscript for publication.

Acknowledgements

This manuscript contains parts of the doctoral theses of SG and NE, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany. The authors thank all physicians and nurses of the ICU, Department of Anesthesiology, University Medical Center of the Johannes Gutenberg-University for supporting this work.

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ORIGINAL ARTICLE
Year : 2016  |  Volume : 10  |  Issue : 3  |  Page : 483-487 

Clinical evaluation of the effect of intravenous dexmedetomidine on the hemodynamic response to laryngoscopy and endotracheal intubation in patients undergoing thyroid surgeries

HD Rashmi, HK Komala
Department of Anesthesiology, Adichunchanagiri Institute of Medical Sciences, Mandya, Bellur, Karnataka, India

Date of Web Publication27-Sep-2016

Correspondence Address:
H D Rashmi
No. 4103, “CHIGURU”, Behind PWD Colony, Near Stadium, Hassan - 573 201, Karnataka
India

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0259-1162.179311

   Abstract 


Background: The procedures in anesthesia such as laryngoscopy and endotracheal intubation are the most important skills to be mastered by an anesthesiologist. However, they produce marked cardiovascular responses such as hypertension and tachycardia. Various drugs have been used to suppress this response. One of those is a novel centrally acting α2agonist - dexmedetomidine. It has numerous uses in anesthesia as it is having sedative, analgesic, hypnotic, and opioid sparing effects. It is also known to suppress the hemodynamic response to laryngoscopy and intubation.
Aims: This study is aimed to know the effect of intravenous dexmedetomidine 0.6 μg/kg body weight on hemodynamic response to laryngoscopy and endotracheal intubation in patients undergoing thyroid surgeries.
Setting and Design: Sixty patients of American Society of Anaesthesiologist health status class I and II scheduled for thyroid surgery under general anesthesia were considered in this prospective randomized controlled double-blind study. The study population was randomly divided into two groups with 30 patients in each group using sealed envelopes containing the name of the group and patient is asked to pick up the envelope.
Materials and Methods: Sixty euthyroid patients, scheduled for thyroid surgeries was randomly divided into two groups with 30 patients in each group. Group A (n = 30) received injection dexmedetomidine 0.6 μg/kg body weight and Group B (n = 30) received 10 ml of normal saline. Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) were recorded at regular intervals after intubation.
Results: Statistically significant decrease in HR, SBP, DBP, and MAP were observed in Group A after intubation when compared to Group B.
Conclusion: We conclude that dexmedetomidine 0.6 μg/kg body weight obtunds the hemodynamic responses to laryngoscopy and tracheal intubation in patients undergoing thyroid surgeries.

Keywords: Dexmedetomidine, endotracheal intubation, hemodynamic response, laryngoscopy, thyroid surgeries


How to cite this article:
Rashmi H D, Komala H K. Clinical evaluation of the effect of intravenous dexmedetomidine on the hemodynamic response to laryngoscopy and endotracheal intubation in patients undergoing thyroid surgeries. Anesth Essays Res 2016;10:483-7

How to cite this URL:
Rashmi H D, Komala H K. Clinical evaluation of the effect of intravenous dexmedetomidine on the hemodynamic response to laryngoscopy and endotracheal intubation in patients undergoing thyroid surgeries. Anesth Essays Res [serial online] 2016 [cited 2018 Mar 13];10:483-7. Available from: http://www.aeronline.org/text.asp?2016/10/3/483/179311




   Introduction 


Administration of general anesthesia through laryngoscopy and endotracheal intubation is the most important and essential skill for an anesthesiologist. However, both laryngoscopy and intubation are noxious stimuli and are associated with hemodynamic responses such as hypertension and tachycardia.[1] The increase in the heart rate (HR) and blood pressure are usually transitory, variable, and unpredictable. Intravenous anesthetic induction agents do not adequately suppress the hemodynamic responses produced by endotracheal intubation.[2] Besides minimizing the cardiovascular response, anesthesia induction for patients at risk must also satisfy the following requirements. It should neither be time-consuming nor affect the duration or modality of anesthetic technique and also should not have any effect on the recovery characteristics of the patient.

Dexmedetomidine, a novel α2 agonist, has numerous applications in anesthesia and Intensive Care Unit because it causes sedation, hypnosis, analgesia, and sympatholysis.[3],[4],[5] Various studies have found that dexmedetomidine decreases the hemodynamic response to laryngoscopy and intubation.[6],[7],[8],[9],[10] Different dose has been tried for the same.

Thyroid surgeries pose a multitude of challenges to an anesthesiologist. The commonest implications during such procedures involve the management of a potentially difficult airway, especially in cases of retrosternal goiter, and an enlarged thyroid gland compressing over the trachea for a prolonged duration.[11],[12],[13] Very few literature are available on the usage of dexmedetomidine for thyroid surgeries.

Hence, this study was aimed at studying the effectiveness of intravenous dexmedetomidine, 0.6 µg/kg body weight on hemodynamic response to laryngoscopy and endotracheal intubation in patients undergoing thyroid surgeries.


   Materials and Methods 


A prospective, randomized, controlled, double-blind study was done at Adichunchanagiri Institute of Medical Sciences Hospital, BG Nagar, using intravenous dexmedetomidine 0.6 µg/kg body weight for attenuation of hemodynamic response to laryngoscopy and endotracheal intubation in patients undergoing thyroid surgeries during a period of 1 year between January 2015 and December 2015.

The study was undertaken after obtaining ethical committee clearance as well as informed consent from all patients. Sixty euthyroid patients, scheduled for elective thyroid surgeries under general endotracheal anesthesia belonging to American Society of Anaesthesiologists (ASA) physical status I and II were selected for the study. As all 60 patients were taken for thyroid surgeries electively, preoperative optimization of thyroid function was done adequately. All patients were in euthyroid status before taking up for surgery.

The following patients were excluded from the study, those with cardiac, renal, hepatic, cerebral diseases and peripheral vascular diseases, known history of sensitivity and contraindications to drugs used, noneuthyroid at the time of surgery, patients with hypertension and diabetes mellitus, patients coming for emergency surgeries, anticipated difficult airway, pregnant females, and time for laryngoscopy and intubation exceeding 15 s.

Patients with relatively large swelling of thyroid were not considered for the study anticipating difficult airway. Furthermore, patients on beta blockers were not considered for the study as it can interfere in the hemodynamic variables after administration of dexmedetomidine.

Routine investigations such as hemoglobin, white cell and platelet count, urea and electrolytes, and specific investigations such as thyroid function tests, serum calcium, chest X-ray, electrocardiogram (ECG), indirect laryngoscopy, and X-ray anteroposterior and lateral view of the neck was done in all patients.

The study population was randomly divided into two groups with 30 patients in each group using sealed envelopes containing the name of the group and patient is asked to pick up the envelope. The envelope was opened by a senior anesthesiologist who was assigned to prepare the solutions and was not involved with the study. Group A (n = 30) received injection dexmedetomidine 0.6 µg/kg body weight diluted to 10 ml of normal saline, administered intravenously over 10 min. Group B (n = 30) received 10 ml of normal saline, administered intravenously over 10 min.

All patients included in the study were premedicated with tablet alprazolam 0.5 mg and tablet ranitidine 150 mg orally at bedtime the previous night before surgery. They were kept nil orally 10 pm onward on the previous night.

On arrival of the patient in the operating room, an 18-gauge intravenous cannula was inserted, and an infusion of 500 ml Ringer lactate was started. The patients were connected to Star Plus Larsen and Toubro India Limited, multiparameter monitor which records HR, noninvasive measurements of systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and continuous ECG monitoring and oxygen saturation. The baseline SBP, DBP, MAP, and HR were recorded.

After recording the baseline readings, patients in Group A, received dexmedetomidine 0.6 µg/kg body weight diluted in 10 ml normal saline intravenously over 10 min using syringe pump, 10 min before induction. Patients in Group B received normal saline 10 ml intravenously over 10 min using syringe pump, 10 min before induction.

The study drug was prepared by the senior anesthesiologist who was not involved in the study and as such, the observer as well as patient was blinded for the study.

All patients were premedicated with injection midazolam - 0.02 mg/kg body weight and injection fentanyl 1 µg/kg body intravenous (i.v.) after test drug administration. Then patients were preoxygenated for 3 min via a face mask with Bain's circuit. Anesthesia was induced with injection thiopentone as a 2.5% solution, in 25 mg increments till the loss of eyelash reflex. Endotracheal intubation was facilitated with 1.5 mg/kg i.v. succinylcholine 1 min before laryngoscopy and intubation. Laryngoscopy and intubation were performed using Macintosh No. 3 blade lasting for not more than 15 s and after confirmation of bilateral equal air entry and EtCO2, the endotracheal tube was fixed.

Anesthesia was maintained using 66% nitrous oxide and 33% of oxygen with 1% isoflurane. After the patients recovered from succinylcholine, the further neuromuscular blockade was maintained with vecuronium 0.05 mg/kg body weight initially and 0.5 mg increments as and when required. At the end of the procedure, patients were reversed with injection neostigmine - 0.05 mg/kg body weight and injection glycopyrrolate - 0.01 mg/kg body weight.

The cardiovascular parameters were monitored in the following time interval basal-before giving study drug, 1 min after laryngoscopy and intubation, 5 min after laryngoscopy and intubation and 10 min after laryngoscopy and intubation.

Statistical analysis

A sample size of 25 patients was needed to detect an intergroup difference of at least 10% in BP and HR with a power of 0.80 and α of 0.05. To make good for attrition rate, a total number of 30 patients in each group were included for the study. The independent samples t-test procedure compares means for two groups of cases. The crosstabs procedure forms two-way and multi-way tables and provides a variety of tests and measures of association for two-way tables. Repeated measures ANOVA analyzes groups of related dependent variables that represent different measurements of the same attribute.

SPSS for windows (version 17.0) (SPSS Inc., Chicago II, USA) was employed for data analysis. P <0.05 was considered as significant and P < 0.01 was considered as highly significant.


   Results 


Sixty euthyroid patients belonging to ASA physical status I and II undergoing thyroid surgeries were included in the study. As shown in [Table 1], patients in both groups were comparable with respect to baseline demographic characteristics.

As shown in [Table 2], the basal mean HR was comparable in both groups. Statistical evaluation between the groups showed highly statistically significant (P < 0.001) fall in the mean HR in Group A compared to Group B after intubation at 1st min, 5th min, and 10th min.
Table 2: The intergroup comparison of mean heart rate (bpm) changes in response to laryngoscopy and intubation between Group A and Group B

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As shown in [Table 3], the basal mean SBP were comparable in both groups. Statistical evaluation between the groups shows highly statistical significant fall (P < 0.001) in the mean SBP in Group A when compared to Group B, after intubation at 1st min, 5th min, and 10th min.
Table 3: The intergroup comparison of systolic blood pressure (mmHg) changes in response to laryngoscopy and intubation between Group A and Group B

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As shown in [Table 4], the basal mean DBP were comparable in both groups. Statistical evaluation between the groups shows highly statistically significant decrease (P < 0.001) in the mean DBP in Group A when compared to Group B, after intubation at 1st min, 5th min, and 10th min.
Table 4: The intergroup comparison of diastolic blood pressure (mmHg) changes in response to laryngoscopy and intubation between Group A and Group B

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As shown in [Table 5], the basal mean MAP was comparable in both groups. Statistical evaluation between the groups shows highly statistical significant fall (P < 0.001) in the mean MAP in Group A when compared to Group B, after intubation at 1st min, 5th min, and 10th min.
Table 5: The intergroup comparison of mean arterial pressure (mmHg) changes in response to laryngoscopy and intubation between Group A and Group B

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   Discussion 


Different doses of dexmedetomidine have been used to find the effectiveness for blunting hemodynamic responses to laryngoscopy and intubation.[6],[7],[8],[9],[10] In our study, following laryngoscopy and intubation at 1 min, the mean HR increased by 36 bpm in the Group B whereas in Group A the mean HR increased by only 4 bpm which is statistically highly significant (P = 0.000) when compared to control group (Group B). At 5th min, the increase in mean HR in the control group (Group B) sustained, and it was 23 bpm, whereas in Group A there is a decrease in HR by 3 which is statistically significant. Similar observations were made by Scheinin et al.[6] and Jaakola et al.[7] At 10th min, there was an increase in HR by 13 bpm in control group compared to decrease in the HR by 4 bpm in Group A, which was statistically significant. Our study compares with the studies done by Basar et al.[9]

In our study, it is seen that there is highly significant fall in the SBP in Group A at 1st min, 5th min, and 10th min following laryngoscopy and intubation compared to control group (P = 0.000) wherein there was an increase of SBP of 29 mmHg, 11 mmHg and 1 mmHg at 1st min, 5th min, and 10 min following laryngoscopy and intubation respectively which is comparable with other studies.[6],[7],[8],[9],[14],[15]

After laryngoscopy and intubation, there is an increase of DBP by 21 mmHg in the control group which gradually decreased to near basal values by 10th min. In Group A, there is an increase in DBP at 1st min by 8 mmHg and 5 mmHg respectively. However, there is a decrease in DBP by 9 mmHg and 11 mmHg at 5th min and 10th min in Group A compared to basal values which are statistically highly significant. Similar observations were noted in other studies.[7],[15],[16]

Furthermore, we found that there was a significant decrease in MAP values by 11 mmHg and 14 mmHg, respectively in Group A after intubation at 5th and 10th min, respectively when compared to Group B. Similar observations were noted in other studies.[15],[16]

In 2012 Patel et al.,[14] conducted a similar study to assess the effect of i.v. dexmedetomidine on perioperative hemodynamics and also postoperative recovery in elective surgical procedures with continuous monitoring of depth of anesthesia by entropy analysis.

They noted that dexmedetomidine significantly attenuates stress response at intubation with lesser increase in HR (10% vs. 17%), SBP (6% vs. 23%), and DBP (7% vs. 20%) as compared to the control group (P < 0.05).

Authors concluded that dexmedetomidine attenuates various stress responses during surgery and maintains the hemodynamic stability when used as an adjuvant in general anesthesia.

In 2012, Sulaiman et al.[17] conducted a prospective, randomized, double-blind controlled clinical trial of dexmedetomidine for attenuation of stress response to endotracheal intubation in 60 adult patients on beta blockers, scheduled to undergo elective off-pump coronary artery bypass grafting.

Authors noted that there was a statistically significant lower value of HR, SBP, DBP, and MAP in the dexmedetomidine group when compared with the control group. There was no incidence of hypotension or arrhythmias observed during the study period in any group.

They concluded that pretreatment with dexmedetomidine 0.5 µg/kg as 10 min infusion before induction of anesthesia was a safe and effective method to attenuate the hemodynamic response to the laryngoscopy and intubation in patients scheduled for elective off-pump coronary artery bypass surgery.

In 2016 Santosh and Mehandale [18] studied the effect of dexmedetomidine on duration and quality of analgesia produced by bilateral superficial cervical plexus block (BSCPB) with 0.5% ropivacaine in patients undergoing thyroid surgeries. Authors concluded that the combination of 0.5% ropivacaine and dexmedetomidine for BSCPB provided significantly prolonged and better quality of postoperative analgesia and patient satisfaction than with 0.5% ropivacaine alone in patients undergoing thyroidectomy.


   Conclusion 


We conclude that dexmedetomidine 0.6 µg/kg body weight significantly obtunds the hemodynamic responses to laryngoscopy and tracheal intubation in patients undergoing thyroid surgeries.

Limitation of the study

In our study, we could not measure the plasma concentration of dexmedetomidine related to its dose as the facility is not available in our institution. Hence, we were unable to study the dose-effect relationship of the drug. Sedation score is not measured in our study which is also the limitation of the study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]

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