Effectiveness of Enzyme Spray Intervention on Thirst Relief in Patients With Endotracheal Intubation

This study addresses the high prevalence (66%-70%) of thirst among intensive care unit (ICU) patients with endotracheal intubation, a symptom associated with oral mucosal dryness, nil per os (NPO) status, oxygen therapy, and medication effects. Unrelieved thirst may contribute to anxiety, delirium, and unplanned extubation. Current clinical practices, such as cold water or saline sprays, generally provide only short-term relief, while direct oral water administration may increase the risk of choking or aspiration. Enzyme-based saliva substitutes, which mimic components of natural saliva and may help maintain oral moisture, show potential benefits; however, evidence in ICU populations remains limited.

This randomized controlled trial with blinded outcome assessment was conducted in a surgical ICU at a medical center in southern Taiwan. Eligible participants were adult patients (≥18 years) with endotracheal intubation expected to exceed 24 hours, a baseline thirst intensity score (NRS-I) ≥3, and the ability to communicate. A total of 76 participants were randomly assigned in a 1:1 ratio to either the experimental group (enzyme-based oral spray) or the control group (distilled water spray), using sequentially numbered, opaque, sealed envelopes (SNOSE) to ensure allocation concealment.

The intervention was administered following routine oral care within a standardized time window (13:00-15:00). Both solutions were prepared in identical opaque spray bottles using standardized procedures. Participants were not informed of their group allocation; however, because sensory characteristics after oral administration could differ between the two solutions, complete participant blinding could not be assured. Outcome assessments were performed by trained research nurses who were blinded to group allocation. The protocol included 12 sprays per session (approximately 1.56 mL), delivered to four standardized intraoral sites, with outcomes monitored over a 4-hour period.

Thirst intensity was measured using the Numerical Rating Scale-Intensity (NRS-I), and thirst distress was measured using the Numerical Rating Scale-Distress (NRS-D). Both outcomes were assessed at baseline (T0) and at 30, 60, 120, and 240 minutes post-intervention (T1-T4) by blinded outcome assessors to evaluate changes in thirst symptoms and the persistence of symptom relief over time. No biological specimens were collected; data were obtained from self-reported measures and electronic medical records, with strict de-identification and secure storage procedures.

This study was considered minimal risk. Predefined safety criteria required immediate discontinuation of the intervention if adverse events such as discomfort, choking, respiratory deterioration, or other clinically significant events occurred. Data were analyzed using generalized estimating equations (GEE) to evaluate group, time, and group-by-time interaction effects while accounting for correlations among repeated measurements. The study aimed to provide evidence to inform thirst management, enhance patient comfort, and support clinically feasible nursing care for patients with endotracheal intubation in critical care settings.