Laryngoscopy and tracheal intubation cause undesirable hemodynamic responses, including increased arterial blood pressure and heart rate. The hemodynamic response can exacerbate some risks, such as myocardial infarction and stroke, especially in elderly patients. During tracheal intubation, the stimulation of the oropharyngeal and laryngeal structures that are rich in sympathetic nerves may cause undesired effects. Various other risk factors include patient characteristics, opioid use during induction and type of intubation device, all of which may induce changes in hemodynamic response.
The aging process can alter hemodynamic responses related to tracheal intubation by increasing cardiac rhythm abnormalities such as prolongation of the QT interval on electrocardiogram (ECG) and changes in cardiac function. These adverse effects may increase during anesthesia and surgery. Thus, it is important to maintain hemodynamic stability, particularly during induction and intubation.
The QT interval can describe as the time between the beginning of the Q wave and the end of the T wave in the ECG. The prolongation of the QTc interval can lead to serious ventricular arrhythmias and perioperative cardiac arrest. Laryngoscopy and intubation may cause changes in cardiac repolarization and prolongation of QT interval via a sympathetic response.
The McGRATH MAC videolaryngoscope (McGRATH MAC, Aircraft Medical Ltd., Edinburgh, UK) is a new intubation device. It has a blade and handle like a Macintosh laryngoscope and a small camera and light source at the tip of the blade. The McGRATH MAC videolaryngoscope provides a clear view of the vocal cords and laryngeal tissues with a liquid crystal display attached to the tip of the blade. Compatibility of the oral and pharyngeal axes is required to see the glottis with a Macintosh laryngoscope; however, this manipulation is not required with the McGRATH MAC videolaryngoscope.
Our hypothesis was that intubations with the McGRATH MAC videolaryngoscope in elderly patients would produce less hemodynamic responses and ECG changes than the Macintosh direct laryngoscope. The objective of the study was to compare hemodynamic and ECG changes after tracheal intubation using either the McGRATH MAC videolaryngoscope or the Macintosh direct laryngoscope in elderly patients.
This prospective, randomised, double‐blind study was approved by the Malatya Clinical Research Ethics Board (number 2015/125). The
Patients who had a limited mouth opening, a Mallampati score of four, a difficult airway scenario, hypertension, cardiac disease, and who were known to have a long QT interval (>440 ms), and/or had used drugs known to prolong the QT interval (tricyclic antidepressants, etc.), and those who had a device malfunction during ECG acquisition were excluded from the study.
The randomization of cases was made using a web‐based randomization sequence. The patients were divided into two groups: patients who were intubated using the McGRATH MAC and were allocated to the videolaryngoscope group (Group V, n = 45) and patients who were intubated using the Macintosh direct laryngoscope and were allocated to the direct laryngoscope group (Group L, n = 45).
Age, gender, height, weight, body mass index, and ASA were noted. No premedication was performed. ECG, noninvasive blood pressure and pulse oximeter (SpO2) monitoring (Infinity Delta monitor, Dräger medical system) were performed in the operating room. After 3 min of preoxygenation with 100% oxygen, general anesthesia was induced with 1.5 mg/kg of propofol and 1 μg/kg of fentanyl, and 0.6 mg/kg of rocuronium was applied as a paralytic. Neuromuscular block monitoring was performed using the Train‐of‐Four technique (TOF Watch S monitor; Organon, Dublin, Ireland). When the TOF ratio was 0/4 at the end of the rocuronium application, the patients were intubated based on the study groups. All intubations were performed by a single anesthetist who had received 3 years of anesthesia training, had experienced with the use of Macintosh laryngoscopes, and had practiced at least 20 intubations with the McGRATH MAC videolaryngoscope. In both groups, a silicone‐based lubricant was placed on the endotracheal tubes, which contained a stylet. Endotracheal tubes in sizes 7.5 mm and 8.5 mm for women and men, respectively, were used for endotracheal intubation. After endotracheal intubation, anesthesia was maintained with 2% sevoflurane, 60% nitrous oxide, and 40% oxygen.
Both the anesthetist who collected the data and the patients were blinded to the study. An anesthetist recorded airway assessments, preoperative patient characteristics, and data. To achieve blinding, the anesthetist left the operating room while the intubation was performed. Because the intubation was performed after the induction procedure, the patients did not know which study group they were contained within.
Systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR) and SpO2 were recorded before induction with anesthesia (baseline), immediately after induction, and at 1 min, 3 min, and 5 min after intubation, with simultaneous ECG. Cormack‐Lehane and Mallampati scores, intubation times, number of intubation attempts, and whether external laryngeal pressure was needed were recorded. Complications related to intubation (oral mucosal hemorrhage, esophageal intubation, desaturation) and post‐extubation hoarseness or sore throat were noted.
All ECGs were taken with a standard 12‐lead with a paper speed of 50 mm/s. Each ECG record was evaluated by manual interpretation. All T wave deflections were measured by determining the isoelectric line return point of the T wave which started from the J‐point. If U waves were present, the lowest point of the junction of the T and U wave was considered as the end of the T wave. Patients where the exact end of the T wave could not be determined were removed from the study. The (QTc = QT/RR[1/3]) was used to correct the QT interval in terms of velocity.
Intubation time was recorded as the time from placement of the Macintosh blade or McGRATH MAC videolaryngoscope blade into the mouth to the time of seeing end‐tidal CO2 exposure on capnography. If the intubation failed, then the duration of each attempt was aggregated, with a maximum of three attempts allowed.
The primary outcome of the study was to assess mean blood pressure. The secondary outcomes included QTc interval changes and heart rate. All patients were taken to the postoperative care unit at the end of the surgery, where the presence of hoarseness and sore throat were recorded.
Based on this study, a mean difference of 12(SD 20) ms in the QTc interval immediately after tracheal intubation between the groups was considered to be clinically significant. We calculated that the sample size required to detect this difference at an α level of 0.05 required at least 45 patients in each group with 80% power. Thus, we included 90 patients to compensate for possible attrition.
All data were stored on a disk and were analyzed with SPSS (Version 24.0, SPSS Inc, Chicago, IL) statistical software. Gender, ASA, external laryngeal pressure, hypoxemia, oral mucosal bleeding, esophageal intubation, hoarseness, sore throat, and Mallampati scores were compared with Pearson χ2 tests, Fisher's exact tests and Yates corrected χ2 tests where appropriate. The comparison of heart rate, systolic, diastolic, and mean blood pressures and the QT interval between the two groups was performed using an unpaired Student's t‐test. The comparison of hemodynamic data including repeated‐measures within groups was performed using repeated‐measures analysis of variance (ANOVA), where the calculated F value exceeded the critical value for the 0.05 probability level. A Bonferroni test was used to determine which differences were significant. Quantitative and qualitative data are expressed as the means ± SD and frequencies, respectively. A P‐value less than 0.05 was considered significant.
Ninety‐six patients were initially included in the study. Two patients in Group V and two patients in Group L were excluded due to the problems in the ECG device. One patient in Group V and one patient in Group L were excluded because of the prolongation of the intubation (one patient due to difficult ventilation, one patient due to difficult intubation). Ninety patients were evaluated (Figure ).
There were no statistically significant differences between groups in terms of demographic characteristics (P > 0.05) (Table ).
Patients and intubation characteristics| Variable | Group V (n = 45) | Group L (n = 45) | P value |
| Age (years) | 71.1 ± 5.5 | 71 ± 5.6 | 0.925 |
| Height (cm) | 165.6 ± 8.2 | 165.4 ± 8.6 | 0.910 |
| Weight (kg) | 66.6 ± 9.8 | 65.8 ± 9.31 | 0.692 |
| BMI (kg/m2) | 24.0 ± 3.3 | 23.7 ± 3.7 | 0.633 |
| ASA I/II | 14/31 | 10/35 | 0.346 |
| Gender (female/male) | 20/25 | 20/25 | 0.59 |
| Cormack‐Lehane Scores (I/II/III/IV)(n) | 23/15/7/0 | 23/12/10/0 | 0.64 |
| Mallampati scores (I/II/III/IV)(n) | 22/19/5/0 | 22/16/6/0 | 0.942 |
| Number of intubation attempts 1/2 (n) | 44/1 | 41/4 | 0.357 |
| Time for intubation (s) | 36.1 ± 7.8 | 28.6 ± 6.2 | 0.000 |
QTc intervals were similar between inter‐group and intra‐group comparisons (P > 0.05) (Table ).
QTc intervals for the groups (ms)| Group V (n = 45) | Group L (n = 45) | P value | |
| Baseline | 412.7 ± 18.2 | 407.5 ± 22.8 | 0.234 |
| After induction immediately | 411.7 ± 18.6 | 408.2 ± 28.6 | 0.498 |
| After intubation 1 min | 420.9 ± 18.4 | 415.7 ± 29.7 | 0.327 |
| After intubation 3 min | 421.4 ± 22.3 | 416.9 ± 29.6 | 0.416 |
| After intubation 5 min | 419.4 ± 17.3 | 416.7 ± 24.5 | 0.556 |
When Group L was compared to Group V, there was a significant increase in the first, third, and fifth minutes after intubation in terms of HR. SBP and MBP significantly increased only at 1 min after intubation in Group L compared to Group V. There was a significant increase in DBP in the first and third minutes after intubation in Group L compared to Group V (Table ). In addition, line charts were graphed for all the hemodynamic parameters in Figures .
Hemodynamic changes in two groups| Measures | Group V (n=45) | Group L (n=45) | P value |
| HR (beats/min) | |||
| Baseline | 81 ± 14.6 | 86.3 ± 14.7 | 0.134 |
| After induction immediately | 76.1 ± 12.8* | 79.8 ± 15.1* | 0.525 |
| After intubation | |||
| 1 min | 81.8 ± 14.4# | 93.8 ± 15.1 | <0.001 |
| 3 min | 75.6 ± 13.5*# | 85.7 ± 14.6 | 0.001 |
| 5 min | 70.8 ± 14.3*# | 82.3 ± 13.5 | <0.001 |
| SBP (mmHg) | |||
| Baseline | 139.9 ± 12.7 | 139.8 ± 9.8 | 0.971 |
| After induction immediately | 123 ± 20.7* | 121.1 ± 18.5* | <0.001 |
| After intubation | |||
| 1 min | 130.5 ± 30.1# | 143.7 ± 30.8 | 0.043 |
| 3 min | 119.8 ± 27.3* | 127.3 ± 28.3* | 0.206 |
| 5 min | 113.6 ± 25.7* | 115.3 ± 24.7* | 0.754 |
| DBP (mmHg) | |||
| Baseline | 80.1 ± 7.4 | 82.7 ± 8.5 | 0.119 |
| After induction immediately | 67.9 ± 11.8* | 69.4 ± 11.2* | 0.385 |
| After intubation | |||
| 1 min | 77.2 ± 17.7# | 88 ± 19.7 | 0.008 |
| 3 min | 70.3 ± 15.3*# | 78.3 ± 17.4 | 0.024 |
| 5 min | 65.9 ± 15.8* | 70.5 ± 15.6* | 0.168 |
| MAP (mmHg) | |||
| Baseline | 100.8 ± 7.5 | 102.7 ± 7.7 | 0.257 |
| After induction immediately | 85.3 ± 12.6*# | 88.3 ± 11.8* | 0.048 |
| After intubation | |||
| 1 min | 94.7 ± 21# | 107 ± 22.2 | 0.008 |
| 3 min | 86.9 ± 18.8* | 95.2 ± 21.2 | 0.051 |
| 5 min | 81.9 ± 18.2* | 86.3 ± 18* | 0.246 |
Enlarge this image.The changes in heart rate (HR) with Group V and Group L; data are presented as mean ± SD, with n = 45 in each group. t0, baseline; t1, after induction immediately; t2, after intubation 1 min; t3, after intubation 3 min; t4, after intubation 5 min; *P < 0.05 compared with baseline values after significant repeated measures ANOVA; #P < 0.05 between groups based on the unpaired t test. Group V = videolaringoscope group, Group L = direct laryngoscope group
Enlarge this image.The changes in systolic blood pressure (SBP) with Group V and Group L; data are presented as mean ± SD, with n = 45 in each group. t0, baseline; t1, after induction immediately; t2, after intubation 1 min; t3, after intubation 3 min; t4, after intubation 5 min; *P < 0.05 compared with baseline values after significant repeated measures ANOVA; #P < 0.05 between groups based on the unpaired t test. Group V = videolaringoscope group, Group L = direct laryngoscope group
Enlarge this image.The changes in mean arterial pressure (MAP) with Group V and Group L; data are presented as mean ± SD, with n = 45 in each group. t0, baseline; t1, after induction immediately; t2, after intubation 1 min; t3, after intubation 3 min; t4, after intubation 5 min; *P < 0.05 compared with baseline values after significant repeated measures ANOVA; #P < 0.05 between groups based on the unpaired t test. Group V = videolaringoscope group, Group L = direct laryngoscope group
Enlarge this image.The changes in diastolic blood pressure (DBP) with Group V and Group L; data are presented as mean ± SD, with n = 45 in each group. t0, baseline; t1, after induction immediately; t2, after intubation 1 min; t3, after intubation 3 min; t4, after intubation 5 min; *P < 0.05 compared with baseline values after significant repeated measures ANOVA; #P < 0.05 between groups based on the unpaired t test. Group V = videolaringoscope group, Group L = direct laryngoscope group
There was a significant difference in HR, SBP, DBP, and MAP values immediately after induction and at 3 min and 5 min after intubation compared with the baseline values in Group V (P < 0.05).
In Group L, there was a significant difference in the HR values immediately after induction and the first minute after intubation compared with the baseline values. There was a significant difference in the SBP values immediately after induction and at 3 min and 5 min after intubation compared with the baseline values. There was a significant difference in DBP and MAP values immediately after induction and at 5 min after intubation.
Cormack‐Lehane and Mallampati scores and the number of intubation attempts were similar in both groups. There was a statistically significant difference between Group V (36.1 ± 7.8 s) and Group L (28.6 ± 6.2 s) in terms of intubation time (P = 0.000) (Table ).
In both groups, Cormack‐Lehane (51%) and Mallampati scores (49%) were Grade I in the majority of patients (Table ).
External laryngeal pressure was performed in five patients in Group L and in four patients in Group V (P = 0.90). Esophageal intubation did not develop in any patients, and desaturation was not observed during the intubation process in the study. Oral mucosal bleeding was observed in three patients in each group (P > 0.05). Postoperative hoarseness developed in one patient in Group V, three patients in Group L, and there was no difference between the groups (P = 0.36). Sore throat was observed in 14 patients in Group V and 14 patients in Group L, and there was no difference between the groups (P = 0.82).
In this prospective, randomized, double‐blind study, similar QTc interval changes were observed in the ECGs of patients who were intubated with either the McGRATH MAC videolaryngoscope or the Macintosh direct laryngoscope. The McGRATH MAC videolaryngoscope provided a better hemodynamic response than the Macintosh direct laryngoscope in the early post‐intubation period. However, it increased intubation time.
The hemodynamic response to intubation has been intensively addressed in the anesthesia literature. It has been shown that the force applied during laryngoscopy, the duration of laryngoscopy, and the number of attempts can all increase sympathetic response during laryngoscopy. Videolaryngoscopes do not need to align oral, pharyngeal, and laryngeal airway axes and allow the airway anatomy and vocal cords to be seen more clearly by reducing the lifting force required to expose the glottis. It has also been hypothesized that during laryngoscopy, less mechanical stimulation will occur in the pharyngeal structures, which leads to a reduction in hemodynamic response. However, conflicting results of hemodynamic response have been reported in the literature. Xue et al. did not find any difference in the hemodynamic responses of tracheal intubations in GlideScope video laryngoscopy compared to Macintosh laryngoscopy. The reason for their results may be the use of a stylet in the GlideScope group. It has been explained that reducing the lifting force required to expose the glottis balanced the use of the stylet. In their studies, Siddiqui et al. compared Direct laryngoscopy, GlideScope, and Trachlight devices and standardized the technique of intubation by using a stylet in all intubations. However, they reported that there were not any differences in hemodynamic response.
Yokose et al. reported that McGRATH MAC videolaryngoscopy could reduce the frequency of hypertension after tracheal intubation compared to Macintosh laryngoscopy. Liu ZJ et al. showed that McGRATH videolaryngoscopy with less‐experienced anesthesiologists increased SAP less after intubation. In our study, fewer HR, SBP, and MAP changes were observed in elderly patients with the McGRATH MAC videolaryngoscope.
The prolonged QT interval may cause arrhythmias such as ventricular fibrillation or polymorphic ventricular tachycardia. Although 440 ms is considered to be an extended QTc interval, severe arrhythmias usually occur at QTc intervals of 600 ms or more. Prolonged QRS duration and increased repolarization distribution increase the risk of arrhythmic cardiac death in patients with coronary artery disease. In previous studies, laryngoscopy and tracheal intubation have been shown to increase QTc duration. Erdil et al. showed a prolonged QTc interval following tracheal intubation in their studies of patients with coronary artery disease. In this study, 40% of the patients had the QTc interval values over 440 ms 30 s after intubation. In our study, QTc interval was lower than 440 ms in both groups, which is different from Erdil's results. The probable cause of this difference may be that Erdil et al. investigated patients with coronary artery disease, and we investigated patients without heart disease. Chang et al. investigated the effect of tracheal intubation on the QTc and found that the QTc interval was less than 400 ms on average, which was shorter than our results. The probable cause of the lengthened QTc interval in our study compared to the results from Chang et al. was because our patients were over the age of 65 and as Letsas et al. emphasized, the drug‐induced QT interval is age‐related (> 60 years). In our study, the QTc interval was similar in both groups.
Videolaryngoscopy has been reported to significantly prolong the duration of intubation. Walker et al. found that first‐year anesthesia students had longer intubation times by 17 s with the McGRATH MAC than with direct laryngoscopy. The reason for this difference was attributed to the time loss in the removal of the intubation stylet used in McGRATH MAC videolaryngoscopy. Burdett et al. determined longer intubation times with the McGRATH MAC. The reason for this is that anesthesiologists experienced with Macintosh laryngoscopy should have different skills to effective use of the McGRATH MAC videolaryngoscope. The duration of intubation obtained with videolaryngoscopy in our study was longer than that of direct laryngoscopy and this result coincided with other studies. However, Frohlich et al. reported the duration of intubation as 104 s in the McGRATH MAC videolaryngoscope group, which is quite longer (36 s) than our outcomes. The probable cause is that Frohlich et al. conducted their study with 10 anesthetists, who had performed intubation with a videolaryngoscope at least five times. However, in our study, intubation attempts were performed by a single anesthetist who was more experienced in using the McGRATH MAC videolaryngoscope, which may be the reason of the difference.
Our study has few limitations. Ideally, invasive arterial monitoring could be more useful to see the instantaneous changes in hemodynamic measurements. However, invasive arterial monitoring for conscious patients without coronary artery disease is not preferred in our routine practice. Therefore, all blood pressure monitoring was performed noninvasively in our study. The second limitation was that all ECG measurements were obtained manually rather than by computer‐assisted calculations. This was because we did not have the necessary equipment for computer‐aided calculations.
In conclusion, when the McGRATH MAC videolaryngoscope was compared with the Macintosh direct laryngoscope in elderly patients, the McGRATH MAC videolaryngoscope decreased the hemodynamic fluctuations due to tracheal intubation but did not make a difference in the QTc interval on ECG. The duration of intubation was found to be longer with the McGRATH MAC videolaryngoscope. We believe that intubation in elderly patients with McGRATH MAC videolaryngoscopy produces less hemodynamic changes and can safely be used.
All authors declare no conflicts of interests.
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