Caudal block for postoperative analgesia in pediatric populations may result in an increase in intracranial pressure when performed with a high volume of local anesthetic, or at certain concentrations of anesthetic, according to a study recently published in the British Journal of Anaesthesia.1
Caudal blocks are increasingly being used in the pediatric population to provide pain control after abdominal surgery. A 2015 retrospective review of approximately 18,500 infants and children who received caudal block found a low rate of complications (estimated at 1.9%).2 The most common adverse events were blood aspiration and intravascular injection, in addition to block failure.
The current study, a prospective randomized trial, included 80 children, age 6 to 48 months, weighing <16 kg, and scheduled to undergo urological surgery (eg, orchiopexy, inguinal hernioplasty, hydrocelectomy, penoplasty, or fistula repair) at Severance Hospital, Seoul, Republic of Korea. Patients with a history of intracranial pressure or a current ophthalmic condition were excluded from the study.
The patients were randomly assigned to a high- or low-volume of 0.15% ropivacaine (1.5 ml/kg and 1.0 ml/kg, respectively; n=40 for each). Ropivacaine was injected over the sacrococcygeal ligament between the 2 sacral cornua during ultrasonography-guided caudal blocks.
Intracranial pressure was evaluated by measuring both optic nerve sheath diameter (ONSD) using noninvasive ultrasonogaphy, as increases in ONSD were correlated with intracranial hypertension.3 Measurements were taken before the caudal block (T0), immediately after the block (T1), and 10 minutes (T2) and 30 minutes (T3) post-block.
ONSD was significantly higher at T1, T2, and T3 in the high- compared with the low-volume ropivacaine group (P <.003). In both groups, ONSD was increased at all time points, compared with baseline levels (P =.011 at T2; P =.001 at T3).
The most acute increase was observed at T2, with mean changes in ONSD of 0.82 mm and 0.59 mm in the high- and low-volume groups, respectively, compared with baseline. Increases in ONSD were maintained for at least 30 minutes after the block. Although ONSD did not significantly differ in the 2 groups, changes in ONSD were greater when compared with baseline levels in the high- vs low-volume group.
As the highest increase in ONSD after caudal block was with 1.5 ml/kg vs 1.0 ml/kg of ropivacaine, the researchers concluded that “administration of 1.5 ml/kg of local anaesthetic for caudal block resulted in a greater increase in [intracranial pressure] than administration of 1.0 ml/kg of local anaesthetic.” As indicated by the larger difference in ONSD in the high- vs low-volume groups, “caudal block with 1.5 ml/kg had a significantly longer effect on [intracranial pressure] than that with 1.0 ml/kg volume.”
Applying an ONSD increase cutoff of 5.16 mm for children younger than 1 year and 5.75 mm for children older than 1 year — determined by another study to reveal a diagnosis of increased intracranial pressure4 — the researchers found intracranial pressure to be elevated in 9 children at T1 (4 and 5 in the high- and low-volume groups, respectively), 19 children at T2 (12 and 7 in the high- and low-volume groups, respectively), and 12 at T3 (9 and 3 in the high- and low-volume groups, respectively). The researchers note that these findings “might raise safety concerns regarding caudal block with not only 1.5 mL/kg but also 1.0 1.5 mL/kg, especially in children with intracranial pathologies or risk factors associated with increased intracranial pressure.”
Summary and Clinical Applicability
Caudal blocks appear to increase intracranial pressure from baseline in children undergoing urologic surgery. Caudal blocks that use a higher volume (1.5 ml/kg) of local anesthetic may increase intracranial pressure more than blocks using a lower volume (1.0 ml/kg), but both doses increase pressure in some children to a concerning level. Care should be taken when using caudal blocks in children with an increased risk of intracranial pressure.
Limitations and Disclosures
The study is limited by its small population and single-institution design. It is not clear whether results in this Korean population would be applicable to other countries. In addition, although body temperature may affect intracranial pressure, this was not measured at baseline.
Funding support for the study was provided by Alpinion Medical Systems, which manufactures portable ultrasound equipment. No other conflicts of interest were reported.
- Lee B, Koo BN, Choi YS, Kil HK, Kim MS, Lee JH. Effect of caudal block using different volumes of local anaesthetic on optic nerve sheath diameter in children: a prospective, randomized trial. Br J Anaesth. 2017;118(5):781-787.
- Suresh S, Long J, Birmingham PK, De Oliveira GS Jr. Are caudal blocks for pain control safe in children? An analysis of 18,650 caudal blocks from the pediatric regional anesthesia network (PRAN) database. Anesth Analg. 2015;120(1):151-156.
- Dubourg J, Javouhey E, Geeraerts T, Messerer M, Kassai B. Ultrasonography of optic nerve sheath diameter for detection of raised intracranial pressure: a systematic review and meta-analysis. Intensive Care Med. 2011;37(7):1059-1068.
- Padayachy LC, Padayachy V, Galal U, Pollock T, Fieggen AG. The relationship between transorbital ultrasound measurement of the optic nerve sheath diameter (ONSD) and invasively measured ICP in children. : Part II: age-related ONSD cut-off values and patency of the anterior fontanelle. Childs Nerv Syst. 2016;32(10):1779-1785.