Introduction The substantial compression of the dural sac and the subsequent cranial shift of cerebrospinal fluid caused by a high-volume caudal block has been shown to significantly but transiently reduce cerebral blood flow. The aim of the present study was to determine whether this reduction in cerebral perfusion is significant enough to alter brain function, as assessed by electroencephalography (EEG).

Methods Following ethics approval and parental informed consent, 11 infants (0–3 months) scheduled to undergo inguinal hernia repair were included in the study. EEG electrodes (using nine electrodes according to the 10–20 standard) were applied following anesthesia induction. Following a 5 min baseline period, a caudal block was performed (1.5 mL/kg), whereafter the EEG, hemodynamic, and cerebral near-infrared spectroscopy responses were followed during a 20 min observation period that was divided into four 5 min segments. Special attention was given to alterations in delta power activity since this may indicate cerebral ischemia.

Results All 11 infants displayed transient EEG changes, mainly represented by increased relative delta power, during the initial 5–10 min postinjection. The observed changes had returned close to baseline values 15 min postinjection. Heart rate and blood pressure remained stable throughout the study.

Conclusion A high-volume caudal block appears to increase intracranial pressure, thereby reducing cerebral blood flow, to the extent that it transiently will affect cerebral function as assessed by EEG (increased delta power activity) in approximately 90% of small infants.

Trial registration number ACTRN12620000420943.