A Comparison of McGrath® MAC Versus C-MAC® Videolaryngoscopes in Morbidly Obese Patients Undergoing Bariatric Surgery: A Randomized, Controlled Clinical Trial
Phase: NA
Conditions: Difficult Intubation, Morbid Obesity, Videolaryngoscopy
Sponsor: Inonu University

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A Comparison of McGrath® MAC versus C-MAC® Videolaryngoscopes in Morbidly 
Obese Patients Undergoing Bariatric Surgery: A Randomized, Controlled Clinical Trial 
*Sedat Akbas, Asst. Prof. Department of Anesthesiology and Reanimation, Inonu University 
Medical Faculty, Malatya, Turkey 
Ahmet Selim Ozkan, Asst. Prof. Department of Anesthesiology and Reanimation, Inonu 
University Medical Faculty, Malatya, Turkey 
Erol Karaaslan, Asst. Prof. Department of Anesthesiology and Reanimation, Inonu University 
Medical Faculty, Malatya, Turkey 
 
Address all correspondence to: 
Sedat Akbas, Asst. Prof. Department of Anesthesiology and Reanimation, Inonu University 
Medical Faculty, Malatya, Turkey 
Mail: drsedatakbas@gmail.com 
Phone Number: +905058263912  
Fax Number: +904223410728 
 
A short title: McGrath vs C-MAC in Morbidly Obese Patients 
 
Conflict of Interest:  
The authors declare that they have no conflict of interest. 
Funding Information:  
None 
 
 
 
 
 

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Study Protocol 
 
Protocol: This study was approved by the Local Ethics Committee. We conducted a 
prospective, randomized, controlled clinical study with 80 morbidly obese adult patients 
undergoing bariatric surgery from 8 September to 20 October 2018 at a university hospital. This 
study was prepared in accordance with the Consolidated Standards of Reporting Trials [9]. 
Study Participants: Our study participants (n = 80) were morbidly obese patients with 
American Society of Anesthesiology (ASA) scores of III who were aged 18–65 years old, had 
a BMI ≥ 40 kg/m2, and were presenting for bariatric surgery at our hospital. All surgery patients 
meeting these criteria during the study period were interviewed before surgery to obtain written 
informed consent to participate in the study. Patients who were aged under 18 - over 65 years 
old, pregnant or who had a BMI ≤ 40 kg/m2, an allergy to anesthetic drugs, uncontrolled 
cerebrovascular disease, or drug and alcohol addiction were excluded, as were all patients who 
refused written informed consent. 
Preoperative Procedures: Preanesthetic evaluations were performed on all patients one day 
before surgery. Age, gender, height, weight, BMI, ideal body weight (IBW), ASA physical 
status, and type of surgery were recorded. On the day of surgery, patients were taken to the 
operating room without premedication. Standard monitoring procedures were used, including 
heart rate (HR), noninvasive blood pressure (NIBP), electrocardiogram (ECG), peripheral 
oxygen saturation (SpO2), mean arterial pressure (MAP), and body temperature monitoring by 
esophageal probe. 
General Anesthesia Protocol: A standardized general anesthesia protocol was administered to 
all patients. After preoxygenation (100% 4 L/min O2 for 3 min), patients were induced with 
propofol (1–2 mg/kg), rocuronium (0.8 mg/kg), and fentanyl (0.1 μg/kg) via intravenous (IV) 
route at doses calculated according to IBWs. Mask ventilation and tracheal intubation using 

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either the McGrath MAC (blade size: 4) or C-MAC videolaryngoscopes (blade size: 4) were 
performed by an experienced anesthesiologist who had previously used both 
videolaryngoscopes successfully at least two years (more than 200 times). Also, tracheal 
intubations were performed by both videolaryngoscopes with the blade size 4 and using stylet 
in endotracheal tubes. End-tidal carbon dioxide (EtCO2) was continuously monitored after 
intubation. Tidal volume and ventilation rate were adjusted to maintain the EtCO2 partial 
pressure of arterial blood at 35–45 mmHg. Additional rocuronium was intermittently injected 
according to need based on Train of Four (TOF; Dräger AG, Lübeck, Germany) values. TOF 
responses were assessed by ulnar nerve stimulation and adductor muscle response. Additional 
fentanyl (0.1–0.2 μg/kg) was titrated for analgesia, as needed, if HR and/or MAP increased by 
20% above baseline during surgery. Anesthesia was maintained in both groups by desflurane 
inhalation in a 0.5 O2 oxygen-air mixture. Desflurane was discontinued with the beginning of 
skin sutures and fresh gas flow was changed to 4 L/min of oxygen. In patients who did not 
experience complications during surgery, sugammadex (IV, 2–4 mg/kg; Bridion®, MSD, 
Greenville, USA) was then administrated to reverse residual muscle relaxation at the end of 
surgery. 
Randomization: This study was planned as a randomized prospective study. Randomization 
was performed using MedCalc v. 16 statistical software for Windows (medcalc.com.tr). Eighty 
patients were randomly allocated to two groups: McGrath (n = 40) and C-MAC (n = 40) (Figure 
1. Flow diagram). All patients received standard surgical procedures determined by the same 
team of surgeons with experience in gastroenterology surgery. Patient pneumoperitoneum 
pressure ranged from 10–12 mmHg and pneumoperitoneum levels ranged from 30–45 degrees. 
Surgical management of sleeve gastrectomy and gastric bypass surgeries was not changed in 
any way.  

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Postoperative Management: All patients were transferred to the post-anesthesia care unit 
(PACU) after surgery. Patients were then transferred to the general surgery intensive care unit 
when they achieved a score of 9 or higher on the Modified Aldrete score (range 0–12; scores 
of 9 and above indicate that the patient can be discharged from the PACU) [10]. In all patients, 
postoperative analgesia was achieved using appropriate IV doses of tramadol (0.5–1 mg/kg) 
and paracetamol (1 gr) at the time of beginning skin sutures [11].  
Outcome Measures: Primary outcome measures were time to intubation and incidence for 
successful intubations. Time to intubation was defined as the time from when the 
anesthesiologist picked up the videolaryngoscope to when the anesthesiologist successfully 
placed the endotracheal tube through the vocal cords, which was assessed by the detection of 
meaningful EtCO2 levels using capnography. Also, time to intubation was recorded by another 
anesthesiologist, who accompanied to the study. The characteristics of each tracheal intubation 
were recorded perioperatively for both groups as secondary outcome measures, including the 
position requirements for successful intubations (the position at which successful intubation 
was achieved, neutral vs. sniffing position, i.e., head extension and neck flexion), Cormack 
Lehane grades (laryngeal view during endotracheal intubation with the videolaryngoscope on 
a grade of 1=full view of the glottis, 2=partial view of the glottis, 3=only epiglottis visible, 
4=neither glottis nor epiglottis visible), glottic view (measured as percentage of glottic opening 
[POGO] scores), ease of intubation, patient hemodynamic responses and adverse events during 
intubation. POGO scores were measured on a scale of 1–4 (1 = 75–100% glottic opening; 2 = 
50–75%; 3 = 25–50%; 4 = 0–25%). Ease of intubation was defined on a grade of 1–3 (1 = no 
external manipulation of larynx was required; 2 = external manipulation of larynx was required; 
3 = failed intubation on first two attempts). Incidence, attempts and position for successful 
intubation, Cormack Lehane grades, POGO scores, and ease of intubation were recorded by the 
anesthesiologist who performed the tracheal intubation.  

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Also demographic characteristics, comorbidities, and preoperative airway assessment, 
including each patient’s Mallampati score (1–4), thyromental distance (cm), and mouth opening 
(cm), were recorded one day before surgery. HR, MAP, respiratory rate, and SpO2 were 
recorded at baseline before anesthesia (T0), before intubation (T1), 1 min after intubation (T2), 
2 min after intubation (T3), 3 min after intubation (T4), and 5 min after intubation (T5). In 
addition, adverse events of tracheal intubation, including dental trauma, blood on blade, cuff 
burst, laryngospasm, bradycardia (HR < 65 beats/min), and hypoxemia (SpO2 < 90%), were 
recorded during the 15 min perioperative period. Hoarseness and sore throat were also recorded 
during the first 24 hours after surgery. 
Sample Size: Statistical power analysis was performed based on a pilot study on 14 morbidly 
obese patients in our institution showing mean time to intubation of 45 ± 18.0 s [standard 
deviation (SD)] with the McGrath MAC. For power calculations (OpenEpi, Version 3), equal 
standard deviation for both groups was assumed. To show a difference of 12 s between the two 
groups and with an alpha of 0.05 and two tailed and a power of 80%, we calculated that a 
minimum of 36 patients per group should be included in this study. We ultimately included a 
total of 80 patients to allow for patient drop-out. 
 
 
 
 
 
 
 

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Statistical Analysis:  
Data were analyzed using the Statistical Package for the Social Sciences program (SPSS 22.0, 
IBM). The Kolmogorov-Smirnov normality test was used to test whether quantitative variables 
showed a normal distribution. As some patient preoperative and anesthetic characteristics were 
distributed abnormally, nonparametric statistics was used. Quantitative data are presented as 
mean or standard deviation and categorical data are shown as numbers or percentages. 
Continuous variables were compared between the groups using a Mann-Whitney U test. 
Categorical variables were summarized using frequencies and percentages, and were compared 
between the groups using a Chi-Square test or Fisher’s exact test. A repeated measures ANOVA 
was used to compare hemodynamic data within each group, while an unpaired t‑test was used 
for comparisons between the two groups. Results were evaluated at a 95% confidence interval 
at a significance level of p < 0.05.