Abstract: We included 14 trials in this review, with 1152 randomised participants. The studies were published between 1990 and 2009 and were conducted in the United Kingdom, Egypt, Saudi Arabia, and the United States. The age of participants ranged from 2 to 40 years. Three studies were at an overall high risk of bias, seven studies were at an unclear risk of bias, and we judged four studies to be at low risk of bias. The clinical heterogeneity of the included studies precluded pooling of studies in terms of method of administration of LA (e.g., intraligamental injection, infiltration injection, or topical delivery) and variation in the use of supplementary analgesics and follow-up time. Of the seven studies where administration of LA was by infiltration injection, six studies (very low-quality body of evidence, 542 participants analysed, 1 study had overall high risk of bias, 4 studies had overall unclear risk of bias, 1 study had overall low risk of bias) measured postoperative pain. The results were equivocal. There was a decrease in bleeding and increase in soft tissue damage in the LA groups, but we did not judge this to be clinically significant. In the 2 studies where administration of LA was by intraligamental injection, there was no difference in mean pain scores, and they did not report any soft tissue damage (very low-quality body of evidence, 115 participants analysed, 1 study had overall high risk of bias, 1 study had overall unclear risk of bias). One 3-armed study (very low-quality body of evidence, 54 participants analysed, overall high risk of bias) compared the effects of intraligamental and infiltration LA injection with no treatment. There was no evidence of a mean difference in pain, distress, or postoperative anxiety among the three groups. Four studies (very low-quality body of evidence, 343 participants analysed, 2 studies had overall low risk of bias, 2 studies had overall unclear risk of bias) evaluated the effects of topical LA compared with no treatment or placebo. One study (overall unclear risk of bias) with a no-treatment comparator reported lower mean pain in the LA group; all other studies reported no difference in mean pain scores. Two studies reported on bleeding (overall unclear risk of bias): One study reported a clinically insignificant increase in bleeding with no treatment; the other reported no difference. None of the studies reported on participant or child satisfaction. In this review, it was difficult to reach firm conclusions as to the benefit of using local anaesthetic for dental treatment under general anaesthesia. The information reported in the included studies was comprehensive and applicable to the review question, but ultimately it was not sufficient to address the objective of the review. We were unable to pool the included studies in a meta-analysis because of substantial variation in outcome measures, interventions, and treatment types. The use of supplementary analgesia further obscured the effect of local anaesthetics. Based on the literature review and the results of this review, we recommend further randomised controlled trials that minimise bias through adequate allocation concealment and blinding of participants and assessors, and assess the effect of intraoperative local anaesthetic on the volume and type of anaesthetic used and on the cardiovascular system in participants receiving supplementary analgesics as well. Researchers should give consideration to the impact of any changes on the health and well-being of the participant and report baseline measures of pain or distress, or both, and preoperative anxiety.

Plain-language summary: . The Cochrane Oral Health Group carried out this review and the evidence on which it is based was up-to-date on 2 January 2014. We included 14 studies, which took place from 1990 to 2009 in the UK, Egypt, Saudi Arabia, and the USA. These included 1152 participants aged from 2 to 40 years. Although the 14 studies included addressed our research question, they differed in the way that they delivered the intervention and what they measured. This meant we could not combine their data in our analyses. The results from individual studies for pain, bleeding, and other adverse effects were uncertain. The use of additional different painkillers may have hidden the effect of the LA. Further high-quality trials are needed in order to assess the benefits or harms of LA given to children and young people whilst they are receiving dental treatment under GA. Issues that these trials need to address include local side-effects (e.g., excessive dribbling and accidental lip biting), side-effects on other parts of the body (e.g., the heart), participant and parent satisfaction, dosage, type of anaesthetic, and the effects of extra painkillers (e.g., paracetamol). The quality of the 14 included studies was variable. We assessed three studies as being at overall risk of high bias, seven at unclear risk of bias, and four at low risk of bias.