Abstract
Background and Aims:
Video Stylet (VS) is a new intubating modality that provides real-time video of endotracheal intubation (ETI). This device does not need alignment of the oral, pharyngeal and tracheal axes to view glottis and can be used in patients with limited mouth opening. The aim of this study was to compare flexible fibre-optic (FO) bronchoscope with VS in elective surgical patients in apparently normal airway patients requiring oral ETI.
Methods:
Sixty patients undergoing elective surgery under general anaesthesia of age group 20–60 years, weight 40–70 kg, American Society of Anesthesiologist 1 and 2 and modified Mallampatti I and II were included in the study. Patients in group FO (n = 30) were intubated by flexible FO bronchoscope, whereas patients in group VS (n = 30) were intubated by VS. Primary outcome measure was time taken for intubation (TTI). Secondary outcome measures were successful intubation, haemodynamic response and post-operative complications if any.
Results:
Average TTI in cases of FO group was 38.2 s (95% confidence interval [CI] 36–41) and in VS group was 19.7 s (95% CI 19–21; P = 0.0001). Three patients required a second attempt for successful intubation in FO group compared to eight in VS group (P = 0.2), with no failures in any group. Haemodynamic response and complications rate were greater in VS group; however, the differences were not statistically significant.
Conclusion:
VS takes lesser time to intubate than flexible FO bronchoscope.
Key words: Airway, flexible fibre-optic bronchoscope, intubation time, Video Stylet
INTRODUCTION
Airway management has always fascinated anaesthesiologists as it is the most challenging task still encountered during clinical practice and the leading cause of anaesthesia-related injury.[1] A number of devices have appeared from time to time with their own unique properties to simplify methods of securing airway and Video Stylet (VS) is one of the relatively newer devices in this category. It is a light weight, reusable, chargeable and portable device with a liquid crystal display module screen for visualisation of vocal cord and upper tracheal rings. Stylet bending angle is more than 90°, and field of view is 80°.[2] The stylet is bent to the 'field hockey-stick' shape (75°–120°) manually after railroading the endotracheal tube (ETT) over stylet.
The aim of the study was to compare the use of flexible fibre-optic (FO) bronchoscope with VS for patients undergoing elective surgery and requiring endotracheal intubation. The primary objective was to compare the time taken for intubation (TTI) by flexible FO bronchoscope in comparison to VS group. The secondary outcome was to see whether VS is comparable in terms of successful intubation, haemodynamic response and post-operative complications if any.
METHODS
Following Institutional Review Board and Ethical Committee approval, sixty patients undergoing elective surgery under general anaesthesia of age group 20–60 years, weight 40–70 kg, American Society of Anesthesiologists 1 and 2 and modified Mallampati I and II were included in the study. Written informed consent was taken from patients. Patients with hyperreactive airway, raised intracranial pressure, known airway pathology or cervical spine injury and those who were potentially full stomach were excluded from the study. Patients in group FO (n = 30) were intubated by flexible FO bronchoscope (Karl Storz, Germany) and in group VS (n = 30) were intubated by VS. Before using the devices, the anesthesiologists practiced 15 intubations with each device on a mannequin.
Randomisation was done preoperatively based on computer-generated random number table. To check the dose of Glycopyrrolate with the main manuscript, injection midazolam 0.04 mg/kg, injection fentanyl 2.0 μ/kg and injection dexamethasone 0.1 mg/kg intravenously 20 min before induction of anaesthesia. In the operating room, standard monitors such as pulse oximeter, non-invasive blood pressure, electrocardiogram and temperature probe were applied. After pre-oxygenation for 5 min, anaesthesia was induced intravenously with injection propofol 2 mg/kg and injection vecuronium 0.1 mg/kg; ETT was lubricated with water-based K-Y jelly, and oral intubation was carried out by one of the two devices with the heads in neutral head position, with two-handed jaw thrust applied by an assistant. If needed neck extension or backward, upward and rightward pressure to be used additionally. For fibreoptic bronchoscope, the scope was inserted till the carina was visualised and then the tracheal tube was railroaded and for Video stylet, the first one or two tracheal ring were visualised before railroading the endotracheal tube. Anaesthesia was maintained on 60% nitrous oxide in oxygen with propofol infusion, injection vecuronium bromide and intermittent positive pressure ventilation and a closed circuit with circle absorber. All intubations were done by an experienced anaesthesiologist. Pulse rate (PR) and mean arterial pressure (MAP) changes from pre-induction to post-intubation values at 0, 3 and 5 min were recorded. Complications such as blood on ETT, sore throat and hoarseness of voice were noted.
Primary parameter was TTI (seconds) calculated from the time the device was introduced into mouth till it was removed after the confirmation of correct placement of ETT by the appearance of an optimal waveform on the capnograph. Secondary parameters were successful intubation, haemodynamic changes such as PR and MAP and complications such as blood stained on ETT, sore throat and hoarseness of voice were also noted. Successful intubation was defined as the appearance an optimal waveform on the capnograph after placement of the ETT. An attempt was defined as one, in which the intubating device was withdrawn from the mouth irrespective of the outcome of procedure. When the oxygen saturation decreased to 92%, the device was removed, and in between the attempts, the lungs were ventilated by bag and mask till the oxygen saturation reached 100%. Failure to intubate was recorded after two attempts.
As no previous study is available known to our knowledge, a pilot study was conducted with five patients in each group. The clinical relevant difference (Δ) was presumed to be 10 s with standard deviation (σ) of 12 s. Results were obtained, and sample size was calculated with the number of patients required per group equal to thirty each with a significance level (Ώ±) of 5% and power of 80% (Ώ2 =1–0.8). The formula used was n = 2 (zΏ±/2 + zΏ2)2 σ2/Δ2.[3] Statistical analysis was performed using Prism windows 6.07 (Graph Pad Software, Inc, USA). Demographic parameters including non-parametric data such as sex and modified Mallampati grade were analysed using Fisher's exact test, and parametric data such as age and weight were analysed using Unpaired t-test. Results' outcome data such as TTI were analysed using unpaired t-test and confidence interval (CI) 95% calculated for mean values. Data for a number of attempts were analysed using Fisher's exact test. The Ώ± level for all analysis was set at 0.05 and P < 0.05 was considered statistically significant.
RESULTS
Eighty patients were recruited between March 2014 and April 2015 [Figure 1]. Patient characteristics and the airway parameters were comparable in the two groups [Table 1]. Average TTI in cases of FO group was 38.2 s (95% CI 36–41) and in VS group was 19.7 s (95% CI: 19–21) which was statistically significant (P = 0.0001). Three patients required a second attempt for successful intubation in FO group compared to eight in VS group; however, the difference was not statistically significant (P = 0.2). No additional manoeuvre was needed in any case. The PR and MAP were higher immediately after intubation in both groups, but the differences were not statistically significant [Figure 2]. There was a significant increase in haemodynamic response in VS group compared to FO group immediately after intubation (P = 0.026). There were three cases of blood on ETT, four cases of sore throat and no case of hoarseness of voice 24 h postoperatively in FO group, whereas in VS group, seven cases of blood on ETT, six cases of sore throat and three cases of hoarseness of voice 24 h postoperatively.
Figure 1.
Consort flow chart
Table 1.
Patient characteristics in Flexible Fibreoptic Bronchoscope (FO) and Video Stylet (VS) groups Continuous data are expressed as mean±SD
Figure 2.
Comparison of haemodynamic changes in both groups before induction and after intubation. Pulse rate in beats/second and mean arterial pressure in mm of Hg. Values recorded just before induction, immediately after intubation and at 3 and 5 min
DISCUSSION
The difference in TTI between the two devices is more than 10 s and statistically significant. One expalanation is that the bronchoscope was inserted till the visualisation of Carina before railroading the ETT, whereas in cases of the VS, visualisation of only the upper tracheal rings was required to railroad the ETT. Another explanation may be that the length of the insertion cord of FO bronchoscope is longer than stylet's length, consuming more time while railroading ETT. Previous studies with OptiScope™ which is a rigid VS had a median intubation time range of 15 (12–19) s,[4] and other study used Clarus™ Video System to intubate simulation airway had a median duration of intubation of 15.5 s[5] that are comparable to our study (19.7 s). The time of intubation in both the cases was taken from the insertion of device into the mouth till the removal of stylet; this could be the reason for a longer duration of intubation in our study as we took intubation time till the appearance of capnograph. The time taken using FO intubation was 38 s which is 20 s less than the time taken in the study conducted by Varghese et al.[6] The reasons for this difference may be because of the age group of patients and the use of intubating devices through which the FO was inserted.
Incidence of successful intubation in the first attempt in cases of FO was 90% compared to 73.3% in VS group which was statistically not different. However our study was not powered to detect this difference. Failures in the VS group may be numerically higher first, due to the preformed shape of stylet that could not be manipulated after insertion in mouth. This was not the case with FO bronchoscope,, as it has a lever to manipulate the direction of tip of insertion cord. Second, the image quality display of VS is inferior, and third, with the VS, there is no provision for suctioning of oral secretions during intubation causing blurring of vision.
There was an increase in PR and MAP just after intubation in both the groups. This could be because first, jaw thrust manoeuvre applied during intubation stimulates a sympathetic response.[7] Second, passing ETT through glottis has a larger impact on haemodynamic variables.[8] However, the difference was not statistically significant from pre-induction values. This could be because we used injection fentanyl intravenously for blunting response to intubation and injection propofol as induction agent causing low blood pressure and PR. Comparison of haemodynamic responses between the two devices showed that there was a significant difference between the two groups immediately after intubation (P = 0.026). Reasons could be increased catecholamine surge due to comparatively more manipulation of vocal cord to centralise the vocal cord by VS in comparison to FO bronchoscope.
The complication rate was higher in VS group as compared to FO group; however, the difference was not statistically significant (P > 0.5). This could be explained by more number of attempts required for intubation. The other reasons could be the rigidity of stylet in comparison to flexible insertion cord of FO bronchoscope causing trauma to vocal cord. The previous study with OptiScope™ has shown the incidence of sore throat equal to laryngoscope.[7]
Both the groups were intubated with two-handed jaw thrust manoeuvre. This improved the easy and rapid insertion of device into the oral cavity. No additional manoeuvre was needed in any case. Previous studies also show the superiority of jaw thrust manoeuvre in improving the glottis view.[9] There is a study which also shows a significant decrease in intubation time and higher success rate.[10]
Video monitor has led to increase the success rate for intubation in comparison to lightwand which is a blind technique. The major advantage of VS is significantly shorter time of intubation that may prove useful when there is a risk of hypoxia.
The VS is less expensive, portable, easy to clean, durable and is an easily available equipment which makes it an alternative to the flexible FO bronchoscope, especially in developing countries where cost of the device is the main limiting factor. This device can be easily used by the beginners. However, further studies with larger sample size are needed to strengthen these findings.
However, our study has a limitation that we did not compare the two devices in difficult airways. Other limitation is that the person using these devices could not be blinded for obvious reasons. Alternatively, it can be used as a lightwand in cases of blood or pharyngeal secretions in oral cavity, where ETT can be guided with the help of glow in midline (semi-blind technique).
CONCLUSION
The VS takes lesser time to intubate than flexible FO bronchoscope. However, further studies with larger sample size are needed to determine its utility in terms of first-attempt success rate and complications, and in the setting of a difficult airway.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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