Abstract: We included 12 studies (803 children) in this review and meta-analysis. We identified three studies that are awaiting classification and two ongoing studies. Trial results show that a longer intubation time was required when indirect laryngoscopy, or videolaryngoscopy, was used instead of direct laryngoscopy (12 trials; n = 798; mean difference (MD) 5.49 seconds, 95% confidence interval (CI) 1.37 to 9.60; I2 = 90%; very low-quality evidence). Researchers found no significant differences between direct and indirect laryngoscopy on assessment of success of the first attempt at intubation (11 trials; n = 749; risk ratio (RR) 0.96, 95% CI 0.91 to 1.02; I2 = 67%; low-quality evidence) and observed that unsuccessful intubation (five trials; n = 263) was significantly increased in the indirect laryngoscopy, or videolaryngoscopy, group (RR 4.93, 95% CI 1.33 to 18.31; I2 = 0%; low-quality evidence). Five studies reported the effect of intubation on oxygen saturation (n = 272; very low-quality evidence). Five children had desaturation during intubation: one from the direct laryngoscopy group and four from the indirect laryngoscopy, or videolaryngoscopy, group. Two studies (n = 100) reported other haemodynamic responses to intubation (very low-quality evidence). One study reported a significant increase in heart rate five minutes after intubation in the indirect laryngoscopy group (P = 0.007); the other study found that the heart rate change in the direct laryngoscopy group was significantly less than the heart rate change in the indirect laryngoscopy, or videolaryngoscopy, group (P < 0.001). A total of five studies (n = 244; very low-quality evidence) looked at evidence of trauma resulting from intubation. Investigators reported that only two children from the direct laryngoscopy group had trauma compared with no children in the indirect laryngoscopy, or videolaryngoscopy, group. Use of indirect laryngoscopy, or videolaryngoscopy, improved the percentage of glottic opening (five trials; n = 256). Studies noted no significant difference in Cormack and Lehane score (C&L) grade 1 (three trials; n = 190; RR 1.06, 95% CI 0.93 to 1.21; I2 = 59%). Evidence suggests that indirect laryngoscopy, or videolaryngoscopy, leads to prolonged intubation time with an increased rate of intubation failure when compared with direct laryngoscopy (very low-quality evidence due to imprecision, inconsistency, and study limitations). Review authors had difficulty reaching conclusions on adverse haemodynamic responses and other adverse effects of intubation, as only a few children were reported to have these outcomes. Use of indirect laryngoscopy, or videolaryngoscopy, might lead to improved vocal cord view, but marked heterogeneity between studies made it difficult for review authors to reach conclusions on this outcome.

Plain-language summary: We reviewed the evidence on how effective indirect laryngoscopy, or videolaryngoscopy, is when compared with direct laryngoscopy for intubation in children from 28 days to 18 years old. We found 12 randomized controlled trials (803 children) that met our inclusion criteria. The evidence is current to November 2015. We reran the search in January 2017 and will include the three studies awaiting classification when we update the review. For intubation, use of indirect laryngoscopy, or videolaryngoscopy, took longer and was more likely to be unsuccessful (very low-quality evidence). No significant difference was found between direct and indirect laryngoscopy when success of the first attempt at intubation was assessed (low-quality evidence). Only a few studies reported the effect of intubation on adverse haemodynamic response, including changes in oxygen saturation, heart rate, and trauma to the mouth and windpipe. Therefore, it was difficult to conclude on the overall adverse effect (very low-quality evidence). Indirect laryngoscopy might provide better views of the vocal cords. We found considerable variation in results from included studies in terms of assessment of intubation time, number of attempts at intubation, number of unsuccessful intubations, adverse effects, and assessments of how well the vocal cords were seen. None of the included studies was funded by a laryngoscope manufacturer, hence minimizing the risk of other bias. The quality of the studies varied, and only a few were of highest quality. For these reasons, we graded the overall quality of evidence as very low.