Effect of caudal block using different volumes of local anaesthetic on optic nerve sheath diameter in children: a prospective, randomized trial

Caudal block is commonly administered for postoperative analgesia in children. Although caudal block with 1.5 ml kg−1 local anaesthetic has been reported to reduce cerebral oxygenation in infants, the effect of caudal block on intracranial pressure (ICP) in children has not been well investigated. Optic nerve sheath diameter (ONSD) correlates with degree of ICP. This study aimed to estimate the effects of caudal block on ICP according to volume of local anaesthetic using ultrasonographic measurement of ONSD in children. Eighty patients, 6- to 48-months-old, were randomly allocated to the high-volume (HV) or low-volume (LV) groups for caudal block with ropivacaine 0.15%, 1.5 ml kg−1 or 1.0 ml kg−1, respectively. Measurement of ONSD was performed before (T0), immediately after (T1), and 10 min (T2) and 30 min (T3) after caudal block. The two groups exhibited significant differences in ONSD according to time (PGroup x Time=0.003). The HV group exhibited significantly greater changes in ONSD from T0 to T2 and T3 than the LV group. However, in both groups, ONSDs at T1, T2 and T3 were significantly greater compared with those at T0, with the highest values at T2. Caudal block with a high volume of local anaesthetic can cause a greater increase in ICP than caudal block with a low volume of local anaesthetic. However, caudal block with 1.0 ml kg−1 of local anaesthetic can also result in a significant increase in ICP. NCT02768493.