Comparison of The Perfusion Index and The Surgical Pleth Index in Detecting The Effectiveness of Caudal Block in Pediatric Patients Undergoing Infraumbilical Surgeries Under General Anesthesia: A Prospective Observational Study

This prospective observational study, will be conducted in Fayoum University hospital after the local Institutional Ethics Committee and local institutional review board approval.

Inclusion criteria

• Children aged 1 to 6 years of either sex
• With American Society of Anesthesiologists (ASA) physical status I-II
• undergoing elective infraumbilical surgery. Exclusion criteria
• parental refusal
• Patients with liver disease (e.g. elevated bilirubin >2mg/dL, albumin<3.0g/dL)
• Patients with renal disease (e.g. serum creatinine >1.5-2mg/dL)
• Cardiac disorders (low EF>50%, sever valvular heart disease)
• Recent respiratory tract infection within 1-2 weeks and bronchial asthma
• Known organic brain disease (cerebral palsy, tumors)
• patients with any contraindication to caudal anesthesia (local infection, coagulation abnormality e.g. INR > 1.5, known structural abnormality e.g. kyphosis)
• Known allergy to local anesthetics. Anesthesia procedure Children will be assessed for enrollment the day before surgery. After enrollment, written informed consent will be obtained from the patient's parents. Children will be fasted according to standard nil per oral (NPO) guidelines: Solids and infant feeds will be withheld for 6 hours, breast milk for 4 hours, and clear fluids for 2 hours before surgery.

There will be three observers in the study: Observer 1 will be a postgraduate in anesthesia and the principal investigator, responsible for screening patients preoperatively to ensure they met the inclusion criteria and will not have any of the exclusion criteria. Observer 2 will be a consultant anesthetist who will administer the anesthesia, Observer 3 will be a postgraduate in anesthesiology who will be unaware of whether the caudal epidural working. Observer 3 will assess the analgesia and the caudal site postoperatively.

An appropriately sized intravenous (IV) peripheral line (22G or 24G) will be secured in the ward, and IV antibiotics will be administered 1 hour before the procedure, all children will undergo routine preoperative preparations by taking full history, general examination and doing investigations: Complete blood count, Coagulation profile, liver and kidney function tests All patients will receive midazolam premedication 0.05 mg/kg (IV) in the preoperative holding area. On shifting to the operating room, standard monitors including electrocardiogram (ECG)monitoring (Lead II and V5), non invasive blood pressure (NIBP), pulse oximetry (SpO2), end tidal carbon dioxide (ETCO2), and volatile anesthetic monitoring will be instituted. NIBP cuff will be attached on the arm opposite to the side of intravenous access in all the patients. The core temperature will be monitored using a nasopharyngeal probe in all the patients and will be maintained between 36.5 and 37.5°C. All these parameters and PI will be recorded by putting pulse oximeter on big toe using Nihon Kohden (Life Scope model BSM-3562, Tokyo, Japan), PI is calculated as (AC × 100/DC%), which is the ratio of infrared light absorbed by pulsing arterial flow (AC) to non-pulsatile signals in blood and tissues (DC). Its range is wide, ranging from 0.02 to 20.