McGrath videolaryngoscope versus Macintosh laryngoscope for tracheal intubation: A systematic review and meta-analysis with trial sequential analysis

Highlights

• We evaluated not only success rate but also glottic visualization and intubation time.

• We conducted a trial sequential analysis.

• The McGrath is superior to the Macintosh in terms of glottic visualization.

• However, it significantly extends intubation time and its success rate is not excellent

• TSA suggests that further studies are necessary to confirm the results of intubation time.

Abstract

Study objective

The McGrath laryngoscope is a novel self-contained videolaryngoscope with a single-use blade. There are several anecdotal reports that the McGrath is superior to the Macintosh laryngoscope for tracheal intubation. However this remains controversial.

Design

Meta-analysis and systematic review.

Setting

Operating room or intensive care unit.

Measurements

A comprehensive literature search was conducted to identify clinical trials that met our inclusion criteria. To qualify, studies had to be prospective randomized trials comparing tracheal intubation between the McGrath and the Macintosh in an adult population. We extracted data on success rate, glottic visualization during intubation, and intubation time from the studies identified. In subgroup analysis, we assessed the influence on each of these parameters which included airway condition (normal or difficult) and operator (novice or experienced). We then conducted a trial sequential analysis (TSA).

Main results

Fourteen articles met our inclusion criteria. The McGrath offered better glottic visualization than the Macintosh (risk ratio, 1.34; 95% confidence interval (CI), 1.25–1.45). However, the McGrath required longer intubation time (mean difference, 10.1 s; CI, 2.74–17.5) and demonstrated similar success rate of tracheal intubation (risk ratio, 1.00; CI, 0.95–1.05) compared to the Macintosh. TSA showed that total sample size reached the required information size (RIS) in glottic visualization and success rate. However, only 15.1% of the RIS was achieved in intubation time. In the subgroup analysis for airway condition and operator experience level, there were no subgroup differences in both glottic visualization and intubation time.

Conclusions

Our meta-analysis suggests that the McGrath is superior to the Macintosh in terms of glottic visualization (GRADE: moderate). However, it significantly extends intubation time (GRADE: very low) and its success rate (GRADE: very low) for tracheal intubation is not excellent. TSA suggests that further studies are necessary to confirm the results of intubation time.

Introduction

The McGrath laryngoscope (McGrath; Aircraft Medical, Edinburgh, Scotland) is a self-contained videolaryngoscope with a single-use blade that has no tube guide. It has a tiny camera and a light source at the tip of the blade powered by a battery contained within the handle, and therefore it is not necessary to have separate cables, screens, or power units. A tiny camera at the tip of the blade with the McGrath videolaryngoscope (McGrath) offers a clear view of the vocal cords, glottis, and surrounding airway anatomy on an LCD screen attached to the handle [1], [2].

Compared with a conventional Macintosh laryngoscope, the efficacy of the McGrath for tracheal intubation was found to be inconsistent. There have been several randomized controlled trials (RCTs) comparing tracheal intubation success rate between the McGrath and Macintosh laryngoscope. Previous studies suggested that the McGrath has higher success rates compared to the Macintosh laryngoscope [1], [3]. Another study showed that the success rate of tracheal intubation with the McGrath in patients with a normal or difficult airway condition is lower compared to the Macintosh laryngoscope [1], [4]. Moreover, tracheal intubation time with the McGrath in a normal airway is shorter than that of the Macintosh laryngoscope [5]. On the other hand, intubation time was longer with the McGrath in patients with an immobilized cervical spine or obstetric patients [1], [6], [7]. In addition, another study showed that the McGrath provides a better view of the glottis compared to the Macintosh laryngoscope [8], [9]. There are also reports stating that there is no difference between the two laryngoscopes [10], [11].

A recently published meta-analysis comparing the McGrath and the Macintosh showed that tracheal intubation success rate did not differ significantly between the two laryngoscopes, with a relative risk (RR) of 3.05 and 95% confidence interval (CI) 0.12–76.4 [12]. However, only 5 studies were included in the meta-analysis. Also, intubation time and glottic visualization with the McGrath were not analyzed.

In this study, we performed a systematic review and meta-analysis of several RCTs to compare the effectiveness between the McGrath and the Macintosh for tracheal intubation in an adult population. We evaluated not only success rate but also glottic visualization and intubation time. We also conducted a subgroup analysis to investigate the effect of airway condition (normal airway or difficult airway) and operators' level of experience (novice or experienced) on tracheal intubation.