Comparison of saddle, lumbar epidural and caudal blocks on anal sphincter tone: A prospective, randomized study

Abstract

Objective To compare the effects of saddle, lumbar epidural and caudal blocks on anal sphincter tone using anorectal manometry. Methods Patients undergoing elective anorectal surgery with regional anaesthesia were divided randomly into three groups and received a saddle (SD), lumbar epidural (LE), or caudal (CD) block. Anorectal manometry was performed before and 30 min after each regional block. The degree of motor blockade of the anal sphincter was compared using the maximal resting pressure (MRP) and the maximal squeezing pressure (MSP). Results The study analysis population consisted of 49 patients (SD group, n = 18; LE group, n = 16; CD group, n = 15). No significant differences were observed in the percentage inhibition of the MRP among the three regional anaesthetic groups. However, percentage inhibition of the MSP was significantly greater in the SD group (83.6 ± 13.7%) compared with the LE group (58.4 ± 19.8%) and the CD group (47.8 ± 16.9%). In all groups, MSP was reduced significantly more than MRP after each regional block. Conclusions Saddle block was more effective than lumbar epidural or caudal block for depressing anal sphincter tone. No differences were detected between lumbar epidural and caudal blocks.

Keywords: Anorectal surgery; anal sphincter tone; anorectal manometry; caudal block; lumbar epidural block; saddle block.

Figure 1.

Flow diagram showing patient numbers at various stages in the prospective, randomized, comparative study of the effects of saddle (SD), lumbar epidural (LE) and caudal (CD) blocks on anal sphincter pressure.

Figure 2.

Percentage inhibition of maximum resting pressure (MRP) and maximum squeezing pressure (MSP) measured by anorectal manometry following regional anaesthetic block. The amount of inhibition caused by the regional anaesthesia (i.e., the pressure drop in the anal canal) was expressed as the percentage of the resting and squeezing pressures. Values are mean ± SEM. *P < 0.05 compared with the SD group, ^†P < 0.05 compared with MRP. SD, saddle block; LE, lumbar epidural block; CD, caudal block.