Diphenhydramine as an adjunct to conscious sedation in bronchoscopy

Intravenous benzodiazepines are commonly used to achieve conscious sedation in outpatient bronchoscopy. Though effective, dose-dependent-adverse events may be encountered with the use of these sedatives. Diphenhydramine, a hypnotic, is sometimes used as an adjunctive agent in bronchoscopy to decrease sedative usage. However, data to support this practice is lacking. Our goal was to determine if adjunctive diphenhydramine significantly decreases doses of benzodiazepine in outpatient bronchoscopy. METHODS: We conducted a single-center retrospective analysis of all outpatient bronchoscopies from November 2013 to February 2016. Subjects included were those who each had two bronchoscopies: no diphenhydramine used (control) versus diphenhydramine used (intervention). The procedure time, total doses of midazolam and opiates (in morphine equivalence) for each procedure were collected. A multiple regression analysis was used to compare differences between bronchoscopy groups in midazolam and opiate use. RESULTS: Of 1164 patients with greater than 1 outpatient bronchoscopies, 61 unique subjects (female 56%) fulfilled the primary inclusion criteria thus resulting to 122 procedures. Mean body mass index was 32 kg/m2. Procedure time was 22.9 ± 16 mins in diphenhydramine group and 23.2 ± 17.8 mins in control group. Mean morphine equivalents administered was 5.6 ± 2.6 mg in diphenhydramine group and 6.2 ± 2.4 mg in control group. Mean midazolam use was 8.4 ± 3.2 mg in diphenhydramine group and 10.2 ± 3.8 mg in control group (difference: -1.795, p-value = 0.005). The mean dose of diphenhydramine used was 38.32 ± 15.12 mg. In a multivariate model, mean midazolam use remained less in the diphenhydramine group after adjusting for procedure time and morphine equivalents, (difference -1.28 mg, p-value = 0.005). CONCLUSIONS: Intravenous administration of diphenhydramine during outpatient bronchoscopy reduces midazolam usage, however, the absolute amount of dose reduction may not be clinically significant