Effect of paediatric caudal injection volume on optic nerve sheath diameter and regional cerebral oximetry

Abstract

BACKGROUND Caudal injections commonly used for neuraxial anaesthesia in children can displace cerebrospinal fluid cranially causing safety concerns in terms of raised intracranial pressure. Optic nerve sheath diameter (ONSD) is a noninvasive surrogate for the measurement of intracranial pressure. Regional cerebral oximetry (CrSO2) can monitor brain oxygenation, which may decrease by a reduction in cerebral flow due to increased intracranial pressure. OBJECTIVES Comparing how caudal injection volumes of 0.8 and 1.25 ml kg−1 influence ONSD and CrSO2 within the first 30 min after injection. DESIGN Prospective, randomised and parallel group trial. SETTING Operating room. PATIENTS Fifty-eight elective paediatric surgical patients between ages 1 and 7 years old, ASA class I or II, without previous intracranial or ocular pathology and surgery appropriate for single-shot caudal anaesthesia. INTERVENTION Single-shot caudal anaesthesia with 0.8 ml kg−1 (group L, n = 29) and 1.25 ml kg−1 (group H, n = 29) of 2 mg kg−1 bupivacaine solution. MAIN OUTCOME MEASURES Optic nerve sheath diameter measured with ultrasonography and regional cerebral oximetry measured by near-infrared spectroscopy before (NIRS), immediately after, 10, 20 and 30 min after the block. RESULTS Mean ONSD values increased from a baseline of 4.4 ± 0.2 mm to a maximum of 4.5 ± 0.2 mm 20 min after injection in group L and from a baseline of 4.5 ± 0.3 mm to a maximum of 4.8 ± 0.3 mm 10 min after injection in group H. Eight of 29 patients in group H and none in group L had an ONSD increase by more than 10%. Both groups had a reduction of less than 2.5% in CrSO2. CONCLUSION Caudal injection with 1.25 ml kg−1 increased ONSD, an indirect measurement of ICP, more than 0.8 ml kg−1 and neither volume caused a clinically important reduction in CrSO2. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT04491032