The Effect of Midazolam on the Normal Sphincter of Oddi: A Controlled Study

Midazolam HCl (Versed) is often used for intravenous conscious sedation in endoscopic retrograde cholangiopancreatography (ERCP) and is increasingly used in endoscopic sphincter of Oddi (SO) manometry. The effect of medications on SO motility should be fully characterized if they are to be used during SO manometry. There has been controversy as to whether midazolam influences SO motility. The aim of this study was to determine the effect of midazolam on the normal SO. The study population consisted of 60 patients presenting with recurrent abdominal pain who were found to have SO basal pressure of less than 40 mmHg on SO manometry. ERCP was performed in the standard fashion using a pneumohydraulic capillary perfused triple-lumen catheter system in a stationary pull-through method from the pancreatic and common bile ducts. In the test group 30 patients received 2 mg midazolam intravenously while the 30 patients in the control group received intravenous saline. SO manometry was performed, with recording of the basal pressure, phasic pressure, phasic amplitude, phasic frequency and ductal pressure before and 3 min after the intravenous infusion. The changes in basal, phasic and duct pressure as well as phasic frequency before and after the administration of saline and midazolam were compared. Midazolam causes a small but statistically significant reduction in basal and peak SO pressure (4 and 19 mmHg respectively), compared with saline. Diagnostic concordance (normal vs. abnormal) between the basal sphincter pressure before and after midazolam was seen in 100 % of patients. Midazolam does not significantly affect phasic amplitude, phasic frequency or duct pressure. Midazolam does not have a clinically significant influence on the accuracy of SO manometry in identifying normal sphincteric motility.