Abstract
Objectives:
Explore hypopharyngeal exposure to abnormally high or low pH during surgery performed under general endotracheal tube anesthesia and to compare results to published normative 24-hour data.
Methods:
Twenty volunteers for this prospective cohort study were recruited from June through September 2013. A wireless Dx-pH monitoring system was used during surgery. A drop from baseline to pH <5.5 was defined as a hypopharyngeal event, with thresholds pH 4.0, 4.5, and 5.0 also examined. Results were compared with supine events published by Chheda et al in 2009.
Results:
The number and duration of hypopharyngeal events <15 minutes with pH below 4.0, 4.5, 5.0 and percentage of surgery time in hypopharyngeal events (from a pH = 5.5 to return to baseline) were similar to comparative data. However, including all duration events (> ≤ 15 minutes), the number and duration of events at all thresholds and the percentage of surgery time in hypopharyngeal events were consistently higher than comparative data. Most analyses with the potential predictive/confounding variables (ie, body mass index, Reflux Symptom Index, Voice Handicap Index-10) yielded nonsignificant results.
Conclusions:
Extended pharyngeal exposure to moderately reduced pH levels (greater than sleeping or resting in a supine position) were documented. Approximately 20% of surgical patients may experience extensive exposure to pH <5.5 (over 1 hour, >30% of surgery time) and an additional 20% may experience moderate exposure to pH <5.5 (5-20 minutes and/or 4% to 10% of surgery time). Additional studies are needed to predict which patients might be at elevated risk for this exposure as well as the impact of this exposure on clinical outcomes.
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