Adverse events and behavioral reactions related to ketamine based anesthesia for anorectal manometry in children

Background: Pediatric patients undergoing anorectal manometry require ketamine anesthesia as other anesthetic agents affect the anorectal sphincter tone. The aim of this prospective observational audit was to evaluate our practice and report the occurrence of adverse events and behavioral reactions related to the use of ketamine, propofol, and midazolam combinations. Methods: Eighty-two consecutive pediatric patients (mean age 8.06 +/- 3.43 years) undergoing anorectal manometry were audited over a 1-year period. After a routine ketamine anesthetic some children were administered midazolam 0.1 mg-kg(-1), at the discretion of the attending anesthetist. Children requiring anal stretch following manometry studies also received propofol 3-5 mg-kg(-1). Intra- and postoperative adverse events, times to spontaneous awakening and discharge from the PACU were noted. Postoperative behavioral reactions were noted in the PACU and at follow-up interviews on the first postoperative day and after a period of 1 month. Results: Following completion of the audit, all patients fell into one of the four groups depending on the anesthetic agents they received: K (ketamine only, n = 16), KM (ketamine and midazolam, n = 10), KP (ketamine and propofol, n = 27), and KPM (ketamine, propofol, and midazolam, n = 29). There was no difference in the occurrence of behavioral reactions between the four groups at the three stages of follow-up. Overall, five patients reported 'new onset' nightmares that had resolved completely at the 3-month follow-up. The time to spontaneous awakening was shorter for K group (17.8 min +/- 0.2)vs KPM group (61.7 min +/- 24.4; P < 0.001). The times to discharge in minutes was also shorter in the K group (54.5 min, IQR 30-75 vs 90 min IQR 78-120; P < 0.001). Administration of propofol appeared to have an antiemetic effect [odds ratio (OR) 0.1, 95% confidence intervals (CI) 0.02-0.58, P < 0.009] in the recovery unit. Conclusions: Our study findings suggest that, besides significantly prolonging time to spontaneous awakening and PACU discharge, neither the use of midazolam, propofol, or combinations is beneficial in preventing the occurrence of behavioral reactions following ketamine anesthesia. Behavioral reactions were common but did not appear to be long-term. Drug combinations with ketamine may have other benefits such as antiemesis.