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ORIGINAL ARTICLE
Year : 2017  |  Volume : 10  |  Issue : 1  |  Page : 117-123

Comparative study between Macintosh versus C-MAC laryngoscopic performance in airway management with dexmedetomidine as stress response attenuator in obese patients


Department of Anaesthesia and Intensive Care, Faculty of Medicine, Al-Azhar University, Cairo; Department of Clinical Pathology, Faculty of Medicine, Al-Azhar University, Cairo, Egypt

Date of Web Publication3-Aug-2018

Correspondence Address:
Abdelazim A.T Hegazy
Department of Anaesthesia and Intensive Care, Faculty of Medicine, Al-Hussein Hospital, Al-Azhar Street, Al-Darasa, Al-Azhar University, Nasr City, Cairo, 00202
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/asja.asja_89_16

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  Abstract 


Introduction Laryngoscopy as well as tracheal intubation causes changes in the hemodynamics of the patient owing to stress response. C-MAC videolaryngoscope (VL) is a relatively recent development that improves the success of tracheal intubation.
Aim The aim of this study was to compare and evaluate the effects of dexmedetomidine for attenuation of hemodynamic responses during laryngoscopy using Macintosh laryngoscope versus C-MAC laryngoscope.
Patients and methods A total of 60 patients, ASA II, 18–60 years old, scheduled for different surgeries under general anesthesia with BMI up to 40 kg/m2 were included in the study. Patients were divided into two groups (30 patients each) and were appropriately positioned, and intubation was done. Hemodynamic stress response to intubation was recorded, and plasma epinephrine level was estimated at baseline and at 1 and 5 min after intubation. Success rate, duration, attempts of intubation, and SpO2% were assessed.
Results Plasma epinephrine level (ng/ml) at baseline and at 1 and 5 min after intubation showed no statistically significant difference in both groups, but there were highly significant differences at 1 and 5 min after intubation compared with baseline values (P<0.0001 and <0.0007, respectively) in each group. Intubation time was longer in ML (17±4.47 s) compared within VL (12±3.4 s). There were no significant differences between both groups after intubation regarding hemodynamic changes, SpO2, or EtCO2.
Conclusion The stress response in both laryngoscopic techniques appears to be the same as detected by the nonsignificant difference in plasma epinephrine levels and hemodynamic changes in both groups, so 1 μg/kg dexmedetomidine is not enough to obtund the stress response completely. C-MAC VL is an efficient and suitable intubating device and provides excellent visualization of laryngeal structures in shorter time with less intubation attempts than Macintosh (Techron Surgical, Sialkot, P, Pakistan) laryngoscopy.

Keywords: dexmedetomidine, difficult airway, direct laryngoscope, morbid obese, stress response, videoassisted laryngoscope


How to cite this article:
Hegazy AA, Abd El-Aziz AF. Comparative study between Macintosh versus C-MAC laryngoscopic performance in airway management with dexmedetomidine as stress response attenuator in obese patients. Ain-Shams J Anaesthesiol 2017;10:117-23

How to cite this URL:
Hegazy AA, Abd El-Aziz AF. Comparative study between Macintosh versus C-MAC laryngoscopic performance in airway management with dexmedetomidine as stress response attenuator in obese patients. Ain-Shams J Anaesthesiol [serial online] 2017 [cited 2018 Dec 11];10:117-23. Available from: http://www.asja.eg.net/text.asp?2017/10/1/117/238485




  Introduction Top


Laryngoscopy as well as tracheal intubation causes changes in the hemodynamics of patients [1]. Dexmedetomidine is a highly specific and selective adrenoceptor α2 agonist [2]. Dexmedetomidine has gained popularity for its sympatholytic, sedative, analgesic, anesthetic sparing, and hemodynamic stabilizing properties [3],[4],[5],[6]. The α-2 : α-1 binding selectivity ratio of dexmedetomidine is 1620 : 1 as compared with 220 : 1 of clonidine [7]. Laryngoscopy and tracheal intubation are more difficult in morbidly obese patients than in patients within the normal weight range [8]. Direct laryngoscopy (DL) is the standard technique for tracheal intubation. In this approach, a DL is used to expose the laryngeal inlet under direct vision or line of sight should be between the airway care provider’s eye and glottis to facilitate placement of a tracheal tube beyond the vocal cords [9]. Videolaryngoscopy (VL) is a relatively recent device that improves the success of tracheal intubation. High-resolution microcameras and portable flat-screen monitors have been used to improve the laryngeal view and success rate of tracheal intubation more than DL. The use of VL has produced a view of the laryngeal inlet independent of the line of sight [10]. VL-guided intubation may have a high success rate in the morbidly obese patients with a difficult airway and that may have less stress for the patient when compared with DL [11].

The aim of the study is to compare and evaluate the effects of dexmedetomidine for attenuation of hemodynamic responses during laryngoscopy using Macintosh laryngoscope (ML) versus C-MAC laryngoscope.


  Patients and methods Top


This prospective, randomized, controlled, and single-blinded study was carried out in Al-Azhar University Hospitals from January 2014 to December 2015. Approval was obtained from the Research/Ethics Committee of Faculty of Medicine Al-Azhar University, and written informed consents had been taken from all patients. A total of 60 adult patients of both sexes with ASA physical status class II, 18–60 years old, with BMI up to 40 kg/m2, who were scheduled for different elective surgeries necessitating endotracheal intubation general anesthesia constituted the population of this study. Patients with criteria of ASA up to III or El-Ganzouri risk index score up to 5 were not included in this study.

Patients were divided into two groups (30 patients each) according to computer-generated randomization technique. Group ML (control group) included patients who were intubated with the conventional ML. Group VL (study group) included patients who were intubated with the videoassisted laryngoscope (C-MAC VL; KARL STORZ GmbH & Co., Tuttlingen, Germany).

Preoperative evaluation

The patients were screened for fitness suitability and airway assessment using El-Ganzouri risk index score ([Table 1]) [12].
Table 1 El-Ganzouri risk index score [12]

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Investigations included blood sampling for laboratory testing as follows: 5 ml of venous blood was drawn from each participant by venipuncture under complete sterile conditions. The collected blood sample was used as follows: 1 ml was placed in EDTA tube for complete blood picture; 1.8 ml was placed in sodium citrate tube and centrifuged, and then the separated plasma was used for assay of prothrombin time (PT) and partial thromboplastin time (APTT); and the rest of the sample was collected in a plain tube, incubated at 37°C, left to be clotted, and centrifuged, and then the separated serum was used for routine laboratory investigations including liver functions, kidney functions, and random blood glucose.

Laboratory testing

  1. Complete blood count was done using automated hematology cell counter Sysmex KX 21 N (Roche Diagnostics).
  2. Liver functions, kidney functions, and random blood glucose were determined by fully automated clinical chemistry auto-analyzer Cobas C311 (Roche Diagnostics, New Jersey, United States).
  3. Assays of PT, international Normalized Ratio (INR), prothrombin concentration, and APTT were performed by semiautomated coagulometer Stago (Diagnostica Stago Inc.).


Others investigations including ECG and chest radiography were done for all patients. Patient monitoring included pulse oximetry, ECG, noninvasive blood pressure, capnography, temperature, and peripheral nerve stimulator. Premedication included atropine (0.5 mg, intramuscular) 30 min before manipulation of the airway and midazolam 1 mg, intravenous, 15 min before the procedure.

Regarding positioning of the patients, the ‘ramped’ position ([Figure 1]) offers better intubation conditions in the morbidly obese patients compared with the ‘sniff’ position, as it creates a better alignment among the oral, pharyngeal, and laryngeal axes [13].
Figure 1 The ramped position [13].

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This position structurally improves maintenance of the passive pharyngeal airway, facilitates bag-mask ventilation, and improves the success of endotracheal intubation.

Anesthesia technique for both groups

All patients received 1 µg/kg of dexmedetomidine over a period of 10 min through infusion pump. During this time, preoxygenation was applied using a face mask and 100% oxygen. Anesthesia was induced by intravenous fentanyl 1 µg/kg (all anesthetic doses were given according to ideal body weight) and propofol 2 mg/kg. Patient’s ventilation using bag and face mask was assessed by chest inflation and capnography before giving rocuronium 0.6 mg/kg to facilitate tracheal intubation. Thirty seconds after drug administration, the patient was manually ventilated by face mask with 100% oxygen and sevoflurane (4%). Tracheal intubation was performed after rocuronium injection, and when train of four (TOF) count became zero on the peripheral nerve stimulator, tracheal intubation was confirmed by the detection of expired carbon dioxide by capnography.

Intubation procedure with the introduction of the C-MAC VL was as follows: ‎with the patient appropriately positioned, the operator used the left hand to introduce the VL into the ‎midline of ‎the mouth and gently advanced it until the D-blade tip pass the posterior portion of the tongue. With the scope now inserted, the operator turns his eyes to the video screen to manipulate the scope and obtain the best view of the glottis; the glottis view was optimized by advancing or withdrawing the laryngoscope slightly while increasing the tilt on the blade to seat the device in the vallecula or on the posterior surface of the epiglottis. When the VL was appropriately positioned, the glottic aperture was seen in the center of the upper third of the videodisplay. The endotracheal tube (ETT) was then ‎inserted under vision until the distal tip of the ETT was judged to be very near the distal tip of the laryngoscope blade. The ETT was fixed by proper tie after suitable place confirmed by auscultation and capnography.

The following parameters were assessed: hemodynamic (heart rate, systolic, diastolic, and mean blood pressure) response to laryngoscopy and endotracheal intubation just before intubation process as baseline and at 1 and 5 min after intubation. Moreover, blood samples for plasma epinephrine analysis were obtained just before intubation process (baseline sample) and at 1 and 5 min after intubation. Epinephrine was estimated by the enzyme-linked immunosorbent assay (ELISA) technique according to using commercial kits of DRG Cat Combi ELISA (New Jersey, United States) (catecholamine combination) (EIA-4309) [14]. Intubation success rate, duration of tracheal intubation (defined as the time from introduction of the laryngoscope in the mouth till confirmation of correct ETT placement with appearance of CO2 waves on capnography), number of intubation attempts, and oxygen saturation were recorded and assessed.

Specimen collection for plasma epinephrine assessment

Because epinephrine release is influenced by several foods and drug, such as vitamin B, coffee, bananas, α-methyldopa, MAO and COMT inhibitors as well as medications related to hypertension, all participants in this study were asked to discontinue them for at least 72 h before specimen collection. Timing of sampling was at baseline and at 1 and 5 min after intubation. Overall, 2 ml of venous blood was collected in EDTA tube and then centrifuged, and the separated plasma was stored at −20°C until used for assay of plasma epinephrine. The kit was supplied by DRG International Inc. (New Jersey, United States).

Principle of the test was follows: adrenaline (epinephrine) was extracted by using a cis-diol-specific affinity gel, (provided with the kit) acylated, and then derivatized enzymatically and then assayed by a competitive ELISA method [15]. Herein, the antigen is bound to the solid phase of the microtiter plate. The standards, controls, and samples and the solid phase-bound analytes compete for a fixed number of antiserum binding sites. After the system is in equilibrium, free antigen and free antigen-antiserum complexes are removed by washing. The antibody bound to the solid phase is detected by an anti-rabbit IgG-peroxidase conjugate using TMB as a substrate. The reaction is monitored at 450 nm. Quantification of unknown samples is achieved by comparing their absorbance with a reference curve prepared with known standard concentrations. The normal range for plasma epinephrine is 0–9.0 ng/ml [16].

Statistical analysis

Data were coded and entered using the statistical package SPSS version 21 (IBM International Business Machines Corporation) is an American Multinational Technology Company Headquartered in Armonk, New York, United States). Data were summarized using mean, SD, median, minimum, and maximum for quantitative variables, and frequencies (number of cases) and relative frequencies (percentages) for categorical variables. Comparisons between groups were done using unpaired t-test in normally distributed quantitative variables, whereas nonparametrical Mann–Whitney U-test was used for non-normally distributed variables.


  Results Top


Demographic data analysis

There were no statistically significant differences between the groups regarding age, weight, height, BMI, sex, and ASA physical status ([Table 2]).
Table 2 Patient’s demographic characteristics

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Regarding plasma epinephrine level (ng/ml)

There were no significant differences between the two groups regarding plasma epinephrine level (ng/ml) at just before intubation process as baseline value and at 1 and 5 min after intubation ([Table 3]).
Table 3 Changes in plasma epinephrine level (ng/ml)

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However, there were highly significant differences (P<0.0017) at 1 and at 5 min after intubation compared with baseline values within each group ([Table 4]).
Table 4 Changes in serum epinephrine level (ng/ml)

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Regarding airway scoring, all patients were asseessed by El-Ganzouri scoring system, and there were no significant differences statistically between the two groups ([Table 5]).
Table 5 Predictors of difficult airway in both groups

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Regarding duration of intubation, number of attempts, and success rate, intubation time was significantly longer in group ML at 17±4.47 s compared with 12±3.4 s in group VL. All patients were successfully intubated on the first attempt in group VL, whereas intubation was successful on the first attempt only in 20 patients, on the second attempt in eight patients, and on the third attempt in two patients in group ML, which was statistically significant. The intubation success rate was 100% in both groups ([Table 6]).
Table 6 Duration of intubation, number of attempts, and success rate in both studied groups

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Regarding changes in hemodynamics (heart rate and blood pressure) in both groups

There were no significant differences between both groups at just before intubation as baseline and at 1 and 5 min reading after intubation regarding heart rate ([Table 7]) and blood pressure ([Table 8]).
Table 7 Heart rate changes (beats/min) in both groups

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Table 8 Systolic, diastolic, and mean blood pressure changes in both groups

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Moreover, there were no significant differences between both groups in end tidal CO2 and O2% at baseline and at 1 and 5 min after intubation ([Table 9]).
Table 9 End tidal CO2 (mmHg) and O2 saturation percentage in both groups

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  Discussion Top


In the present study, there was a statistically significant increase in HR and blood pressure as hemodynamic responses and epinephrine level at 1 and 5 min within each group in comparison with baseline reading, with no significant difference between both groups at the same time intervals. This means that both techniques have nearly the same degree of stress for the patient, which is an important item for selection of the best technique of laryngoscopy. The present study showed that the intubation duration was significantly longer in patients intubated with the ML compared with patients intubated with the C-MAC VL.

The present study demonstrated high success rate with VL on first attempt (100%) compared with ML (66.7%).

The C-MAC VL is a relatively new device with the unique advantage that it provides the possibility to obtain both a DL view and a camera view that is displayed on the video screen, in contrast to many previous VLs that provide an indirect camera view only [17]. Dexmedetomidine has a unique pharmacological profile with sedation, analgesia, sympatholysis, and cardiovascular stability and a great advantage to avoid respiratory depression. Dexmedetomidine increases hemodynamic stability by altering the stress-induced sympathoadrenal responses to intubation during surgery and during emergence from anesthesia [2]. Tracheal intubation is associated with increases in heart rate, arterial pressure, and plasma catecholamine concentrations [18].

In the previous studies, Jungbauer et al. [19], who compared DL with C-MAC VL in 200 obese patients with expected difficult tracheal intubation concluded that the VL provides a significantly better and faster intubation than DL. Nouruzi et al. [20], who did a randomized trial comparing traditional laryngoscope with videoassisted laryngoscope, found that the videoassisted laryngoscope group had significantly shorter mean intubation duration compared with traditional laryngoscope. Moreover, Ruediger et al. [21], who compared endotracheal intubation using the C-MAC VL with the ML in 247 consecutive patients with a potential difficult airway in ICU over a 2-year period during airway management, concluded that endotracheal intubation was associated with a high rate of difficult laryngeal visualization and a high number of repeated intubation attempts in the group intubated by the DL, whereas the use of the C-MAC VL improved the visualization of the glottis and it had a higher success rate for intubation at the first attempt compared with DL. Mosier et al. [22], who investigated the intubations performed in the ICU by mostly trainees with limited experience, concluded that VL significantly improved first attempt and ultimate success rates and grade of laryngoscopic view, and decreased esophageal intubations compared with DL. Yazbek and Aouad [23] reported that dexmedetomidine provides a stable hemodynamic profile by attenuating the stress response during tracheal intubation, which was in line with Vishwanath et al. [2], who reported that pretreatment with dexmedetomidine 1 µg/kg attenuated but did not totally obtund the cardiovascular responses to tracheal intubation after induction of anesthesia. This is in line with Xue et al. [24], who reported that there is no difference in hemodynamic responses to tracheal intubation between the Glidescope VL and ML groups in 57 adults with ASA physical status II.


  Conclusion Top


The stress response in both laryngoscopic techniques appears to be the same as detected by nonsignificant difference in plasma epinephrine levels and hemodynamic changes of both groups, so 1-μg/kg dexmedetomidine is not enough to obtund the stress response completely. C-MAC VL is an efficient and suitable intubating device and provides excellent visualization of laryngeal structures in shorter time with less intubation attempts than ML.

Study limitation

There was a limitation to this study. Although all the intubations were performed by one person, who had sufficient experience in use of C-MAC laryngoscope (>30 times), the investigator had vastly more experience with ML, which may have affected the results as a confounding factor.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9]



 

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