Ultrasonography of optic nerve sheath diameter shows a good level of diagnostic accuracy for detecting intracranial hypertension. The aim of this study is to evaluate the effect of continuous epidural block on intracranial pressure in pediatric patients undergoing osteotomy of lower extremity. Forty patients, aged 4 years to 13 years, receiving epidural analgesia before osteotomy will be divided into bolus group (n=30) and infusion group (n=30). Randomly selected patients of the bolus group are given 0.3 ml/kg bolus/hr of 0.15% ropivacaine for epidural analgesia. In contrast, patients in the infusion group are administered 0.3 ml/kg/hr 0.15% ropivacaine at a constant rate for epidural analgesia. The primary endpoint is the difference in the optic nerve sheath diameter after epidural analgesia measured by optic nerve ultrasonography between groups.

Inclusion Criteria:

• 1. Pediatric patients from 4 to 13 years of age undergoing osteotomy of lower extremity

Exclusion Criteria:

• 1. Patients with contraindications to epidural analgesia (local infection, clotting disorders, anatomical abnormalities, sepsis, etc.)
• 2. Patients with symptoms or signs associated with a history of elevated intracranial pressure or elevated intracranial pressure
• 3. Patients with ophthalmic disease or surgery
• 4. The estimated operation time is less than 180 minutes.
• 5. All parents of the subject are foreigners or illiterate

Participants, care providers and investigators are blinded to group assignment.