Study aim: Determining and comparing the effect of atropine administration before induction of anesthesia on the incidence of delirium and complications in post-anesthesia care unit among children aged 1-6 years old undergoing lower abdominal surgery as compared with the control group Design: A randomized, double-blinding clinical trial, with the parallel groups, Phase 2-3 on 70 patients Settings and conduct: In this randomized double-blind randomized clinical trial study, 70 children who are candidates for lower abdominal surgery presented at Imam Hossein Hospital in Isfahan will be included in the study and will be randomly divided into 2 groups. One group will receive atropine and the other group will receive a placebo before induction of anesthesia. Delirium score, pain score, and hemodynamic parameters of patients will be evaluated and compared between the two groups. Participants/Inclusion and exclusion criteria: Inclusion criteria: age group of 1 to 6 years old; candidate for lower abdominal surgery; class I and II classification of the American Society of Anesthesiologists, and parental consent to participate in the study. Exclusion criteria: having a child with a psychiatric problem including ADHD and depression, and other behavioral disorders. Intervention groups: Intervention group 1: patients in this group receive 0.02 mg/kg of atropine before induction of anesthesia (after dilution with a volume of 0.1 mg per cc). Control group: patients in this group receive 0.02 mg/kg of normal saline (with the same volume in the first group) before induction of anesthesia. Main outcome variables: Delirium; pain; blood pressure; heart rate; percentage of oxygen saturation