BackgroundSurgery can generate significant stress and anxiety in up to 70% of the paediatric population. There are several pharmacological and non-pharmacological strategies to reduce pre-operative anxiety in children, however, they have several side effects and the available information about them is contradictory. The role of clowns and hydroxyzine in the management of anxiety is controversial, with some studies supporting and others contraindicating both strategies.MethodsWe propose a randomised double-blind, controlled clinical trial that will evaluate the effectiveness of both interventions (hydroxyzine and clowns), alone or in combination, to reduce pre-operative anxiety (using the modified Yale scale of preoperative anxiety) in children aged 2–16 years undergoing outpatient surgery (n = 188).Subjects will be randomised into two groups – (1) standard procedure (parental accompaniment) combined with placebo or (2) standard procedure combined with preoperative hydroxyzine. After randomisation, they will be divided by chance into two further groups, depending on the presence of clowns on the patient’s surgery day. Control of pre-operative anxiety will be determined in the four groups by a modified Yale scale of preoperative anxiety and cortisol levels. Compliance of children during induction of anaesthesia, time until anaesthesia recovery, presence of postoperative delirium and use of analgesia until discharge will be also assessed. For additional information, the children, parents and healthcare professionals involved in the study will complete a satisfaction survey.ConclusionsThis study aims to gather evidence on which of these four therapeutic options achieves the highest reduction of pre-operative anxiety with the best safety profile to allow paediatricians and anaesthesiologists to use the most effective and safe option for their patients.Trial registrationClinicalTrials.gov identifier: NCT03324828. Registered 21 September 2017.