The Analgesic Effectiveness and Safety of Upgraded Caudal Dexmedetomidine Doses in Pediatric Hypospadias Surgery.

Background: Dexmedetomidine (DEXM) is a highly selective α2-adrenoceptor agonist that has been used increasingly in pediatric anesthesia. This prospective double blinded randomized comparative study is designed to evaluate the analgesic effect of caudal increasing doses of DEXM 0.5 , 1 , 1.5 , 2µg/kg combined with Levobupivacaine (Levob) 0.125% (ED95% =125%=least effective concentration) in providing pain relief over a 24-h period and lowest surgical stress peak. Study hypothesis: Levobupivacaine 0.125 %( ED95) combined with different increasing doses of dexamedatomedine >1 µg/kg could not add more analgesic & stress response obtundation outcome, but increase side effects (sedation and hemodynamic depression).The peak cortisol level during urology surgery was at the end of the 1st postoperative (PO) hour. Aim of the Study: To detect the optimal analgesic and safe caudal adjuvant DEXM dose associated with the least side effects& stress response modulation, guided by PO Cortisol peak difference in between the study groups during pediatric hypospadias surgery.

Optimal effective dose defined as; the least caudal DEXM dose which produce the best analgesic outcome [least time to 1st analgesic request and lowest rescue analgesic dose (24Hs)] associated with the least stress response (cortisol PO. first One hour peak), least PO sedation, and hemodynamic stability IO. &PO. HR & MAP. The peak cortisol level during urology surgery was at the end of the 1st postoperative (PO) hour.

. Material & Methods A prospective randomized double blinded (drug injector and PO assessor) comparative study will be conducted in Mansoura university hospital after obtaining ethics committee approval and written informed parental consent 164 boys (age 1-6 years, ASA I) scheduled for hypospadias surgery. Exclusion criteria; (Operative time exceeding 3 hours, bodyweight >25kg, bleeding diathesis, infection at the site of block, pre-existing neurological or spinal disease or abnormalities of the sacrum, inability to palpate the sacral hiatus by anatomic landmark palpation technique) or those with a history of allergic reactions to local anesthetics were excluded from the study. Patients will fast for solids 6h and water and 2 hours before surgery. After Patient Preoperative preparation, General anesthesia induction, caudal block and caudal drug injection (Levob plus DEXM) bolus will be injected according to each group as follow;

• Group A will take Caudal Levob 0. 125%+ DEXM 0.5µg/kg.
• Group B will take Caudal Levob 0.125%+ DEXM 1µg/kg.
• Group C will take Caudal Levob 0. 125%+ DEXM 1.5 µg/kg.
• Group D will take Caudal Levob 0. 125%+ DEXM 2µg/kg.

The study outcomes recording: