Incidence of hypoxaemia with intravenous fentanyl and midazolam sedation in adult patients undergoing oral surgery procedures

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Mooney, Eimear
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University College Cork
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Objectives: Respiratory depression and airway compromise may result in serious consequences if untreated during conscious sedation. The primary aim of this study was to investigate the incidence of hypoxaemia (SpO2 ≤94%) in American Society of Anaesthesiologists physical status I & II patients undergoing intravenous sedation with fentanyl and midazolam. The secondary aims included determination of the onset time of hypoxaemic events and significant risk factors for hypoxaemia. Methods: This prospective observational study required 92 patients to achieve a power of 80% at the 5% significance level. A total of 96 patients, (57 female, aged 16-65) met the inclusion criteria and consented to participation. The operator-sedationist delivered a standard dose of 50μg of fentanyl followed by titrated midazolam (range 2-9mg), at a rate no greater than 1mg/min. Oxygen saturations were monitored via pulse oximetry and supplemental oxygen was not given routinely, unless indicated. Verbal or tactile stimulation was performed to encourage respiratory effort when SpO2 ≤94%. Monitoring continued for forty minutes from the time of sedation end point. Data were exported from the ‘BeneVision N12 Mindray’ monitor to Microsoft Excel. Statistical analyses (multi-variate logistical regression) were performed in SAS® (Version 9.4). Results: All participants successfully completed treatment and 94 patients were included in the analysis. 50 (53%) individuals developed hypoxaemia, with 19 (20%) proceeding to severe hypoxaemia (SpO2<90%). Following administration of fentanyl, 90% of hypoxaemic events occurred within 13.6 minutes; the majority (66%) were observed during the pre-operative period. The risk of hypoxaemia increased for each 1% reduction in SpO2 and 1kPa reduction in EtCO2 from baseline by 190% and 192%, respectively. The risk of moderate and severe hypoxaemia increased by 7% (p=0.0003) & 8% (p = 0.0002) respectively, for each added year of age. Conclusions: This study presents information on the incidence of hypoxaemia for multidrug sedation in ASA I & II patients in an outpatient oral surgery department. Whilst the hypoxaemia incidence was found to be 53%, all patients remained responsive to respiratory stimulation, consistent with the definition of conscious sedation. Heightened vigilance for desaturation is required for reductions in SpO2 and EtCO2 from baseline within the first 13.6 minutes following fentanyl administration and with advancing age.
Midazolam , Fentanyl , Hypoxaemia , Conscious sedation , Oral surgery
Mooney, E. 2021. Incidence of hypoxaemia with intravenous fentanyl and midazolam sedation in adult patients undergoing oral surgery procedures. PhD Thesis, University College Cork.