It is generally known that neuraxial anesthesia for adults reduces the demand for hypnotics needed for adequate sedation. Therefore, this study examined the effect of a preoperative caudal block on the general anesthetic requirements for an adequate depth of anesthesia in children.

Twenty children aged 3-5 years, who were set to undergo inguinal herniorraphy, were divided into 2 groups of 10 children each, normal saline and lidocaine groups. Tracheal intubation was performed. After setting up the bispectral index (BIS) monitor, a caudal block was administered to both groups differently, normal saline 0.7 ml/kg was administered to the normal saline group and 1.5% lidocaine 0.7 ml/kg was administered to lidocaine group. The end-tidal concentration of sevoflurane was maintained at 1.5 vol% for 10 minutes in the first patient in both groups, and the BIS value, was measured 6 times every 10 seconds, and averaged. When the BIS was ≥ 50, the end-tidal concentration of sevoflurane was increased by 0.2 vol% in the subsequent patient. When the BIS was less than or equal to 50, the end-tidal concentration of sevoflurane was decreased by 0.2 vol% in the subsequent patient. The MAC_BIS50 in both groups was calculated using probit analysis. Relative median potency analysis was used to compare the results in both groups.

The MAC_BIS50 of sevoflurane was significantly lower with a 1.5% lidocaine caudal block (1.40 vol% [95% CI, 1.25- 1.55 vol%]) compared with the normal saline group (1.77 vol% [95% CI, 1.61-2.00 vol%]).

A preoperative caudal block reduces the demand for sevoflurane required for an adequate depth of anesthesia, as measured by the BIS in children.