This non-invasive dimensionless score index -SPI-reflects the Patients' sympathetic response to surgical stimulation. Its effectiveness in detecting the balance between nociceptor activation and analgesia was not only reported but also, was reported to be superior to the other parameters like blood pressure and heart rate. SPI value is correlated to pain and ranges from 0 to 100, higher values indicate strong surgical stimulus. Its value is obtained from photoplethysmographic amplitude (PPGA) and heart rate (HR) data from pulse oximetry measurement.

Prediction of the severity of postoperative pain using SPI in both adults and children has been reported by several studies. So, the authors hypothesize that dexmedetomidine infusion without giving a bolus dose may affect the SPI in pediatrics undergoing hypospadias repair.

After obtaining Fayoum University's ethical committee permission and as well as the informed consent from the parents, 90 patients aged 1 to 7 years old scheduled for hypospadias repair will be randomly assigned into 2 groups.

Preoperative Assessment:

All patients will be assessed clinically and investigated for exclusion of any of the above-mentioned contraindications.

Perioperative Management:

Patients will receive no premedication. After entering the Operating room, All patients will be monitored using surgical pleth index, arterial blood pressure, pulse oximetry, and electrocardiography. The SPI value will be measured using Datex-Ohmeda (GE Healthcare,Madison,WI 53707-7550 USA) monitoring system.

Inhalational induction of general anesthesia (GA) will be performed with a face mask using sevoflurane 8% and 50% oxygen in the air, and then an intravenous (IV) cannula will be inserted.

Fentanyl will be administered intravenously at 1 μg/kg, atracurium 0.5 mg/kg and an endotracheal tube will be used to secure the airway.

Anesthesia will be maintained with 1% isoflurane, 50% oxygen in the air, and atracurium infusion (0.10 mg/kg).

During the operation, bradycardia is defined as a 30% decrease from the baseline HR, and hypotension is defined as a 30% decrease from the baseline MAP. In these cases, 0.01 mg/kg of atropine and 0.1 mg/kg of ephedrine, respectively, will be given intravenously. Additionally, tachycardia is defined as a 30% increase from the baseline HR, and hypertension is defined as a 30% increase from the baseline MAP. If either of these occurred, 0.1 μg/kg of fentanyl was given intravenously, and then the incidence was calculated and analyzed.

At the end of the surgery, acetaminophen 15 mg/kg IV will be administered to all patients. After completion of the surgical procedure and emergence from anesthesia, the patient will be referred to PACU. Quality of analgesia will be assessed using a face, legs, activity, cry, consolability (FLACC scale) at PACU discharge and 2, 4, 6, 12, and 24 hours postoperatively. Diclofenac sodium 1 mg/kg rectally will be given as rescue analgesia for patients in all study groups in PACU if the FLACC scale > 4. Nurses will be informed about the pain evaluation, to give the patients oral paracetamol 30 mg/kg. The data collectors from nurses will record data. The depth of sedation will be assessed using Ramsy sedation score (RSS) at PACU discharge and 2 hours postoperative by the investigators.

The patient will be discharged from PACU using The Modified Aldrete Score system after an assessment of the patient's activity, respiration, blood pressure, consciousness, and color, A score ≥ 9 is required for discharge from the PACU.

Adverse events like bradycardia hypotension excessive sedation respiratory depression postoperative agitation nausea and vomiting will be recorded during the first 24 hours.

Statistical analysis

• Sample size calculation was done using IBM SPSS version 29 for Windows. A total of 45 children per group are needed to be able to detect an expected difference in the SPI based on previous research.This sample size was estimated using a power of 80% and alpha of 0.05.
• Descriptive statistics for the variables will be presented in the form of mean with standard deviation or median with interquartile range for numeric variables, while frequencies and percentages will be used for categorical variables. Comparison of the two groups will be done after testing for normality of the distribution using Shapiro-wilk test. The analysis will be done using the independent samples t test or using the non-parametric Mann Whitney test for numerical variables. Categorical variables will be compared using Chi Square test or Fisher's exact test. IBM SPSS version 28 for Windows software will be used for the analysis. A p-value of < 0.05 will be considered statistically significant.

Inclusion Criteria:

• Age 1-7years.
• ASA physical status I-II.
• Hypospadias surgery.

Exclusion Criteria:

• Children having a history of mental retardation.
• Developmental delay.
• Allergic to dexmedetomedine.
• Neuraxial anesthesia.
• Cardiovascular disease.

The group's allocations will be only blinded to assessors, data collectors, and parents of children