Effect of local anesthetic volumes in caudal block on intracranial pressure measured indirectly by optic nerve sheath diameter in pediatric patients: A prospective randomized study

Background and Aims: Caudal block (CB) is commonly used for perioperative analgesia in pediatric infra-umbilical surgeries. However, injection of local anesthetic into the epidural space may increase intracranial pressure (ICP) by cranial displacement of cerebrospinal fluid. Optic nerve sheath diameter (ONSD) measured using ultrasonography is a reliable noninvasive surrogate marker for ICP. The present study was aimed to evaluate the effect of two different volumes of local anesthetic used in CB on ICP measured indirectly using ONSD. Material and Methods: This prospective, randomized, double-blinded study included 60 children aged 1–4 years, ASA 1 or 2, undergoing elective infra-umbilical surgery under general anesthesia with CB. Patients were randomized into low- and high-volume groups that received 0.75 ml/kg and 1.25 ml/kg of bupivacaine (1.5 mg/kg) in CB, respectively. ONSD was measured before and immediately after CB and at 5, 10, 20, and 30 minutes thereafter. Hemodynamic and respiratory parameters were also recorded. Results: ONSD increased immediately after CB in both groups, from 4.26 ± 0.20 to 4.36 ± 0.19 mm in the low-volume group ( P = 0.05) and from 4.33 ± 0.18 to 4.63 ± 0.18 mm ( P < 0.0001) in the high-volume group. This transient increase in ICP normalized in both groups by 30 min post block. Intergroup comparison revealed nearly threefold difference between groups in mean percentage increase in ONSD from baseline (group L 2.27 ± 0.44% vs group H 6.94 ± 0.30%). Conclusions: High-volume CB (1.25 ml/kg) causes a significant transient increase in ONSD, suggesting a rise in ICP, whereas low-volume CB (0.75 ml/kg) has minimal effect. Lower volumes may be safer in children where ICP changes are undesirable.