Capillary blood glucose measurement is a routine procedure in emergency departments, but it may cause pain and discomfort because it requires fingertip puncture. Vapocoolant spray is a rapid, noninvasive, and inexpensive method of topical analgesia that may reduce pain during minor procedures. However, its effectiveness during capillary blood glucose testing has not been sufficiently studied. This study aims to evaluate whether vapocoolant spray reduces pain during capillary blood glucose measurement compared with placebo in adult emergency department patients requiring at least two clinically indicated glucose measurements. In this randomized, placebo-controlled crossover trial, participants receive both vapocoolant spray and placebo in a randomized sequence before two separate capillary glucose measurements. Pain is assessed immediately after each procedure using a 100 mm Visual Analog Scale. The findings may help inform practical strategies to improve patient comfort during routine glucose testing in emergency care settings.

This study is a single-center, randomized, placebo-controlled crossover trial conducted in the emergency department of a tertiary care hospital. The study evaluates the efficacy of vapocoolant spray in reducing pain during capillary blood glucose measurement in adult patients who require at least two clinically indicated capillary glucose measurements during the same emergency department visit.

Capillary blood glucose testing is frequently performed in emergency care and is essential for the evaluation and management of many patients. Although it is considered a minor procedure, repeated fingertip punctures may cause pain, discomfort, and procedure-related distress. Vapocoolant spray produces rapid skin cooling and may provide short-term cutaneous analgesia through temporary reduction of sensory nerve conduction. While vapocoolants have been studied in other needle-related procedures, evidence for their use during capillary blood glucose testing remains limited.

Eligible participants are adults aged 18 years or older who require at least two capillary blood glucose measurements for any clinical indication and who provide informed consent. Participants are randomized to one of two intervention sequences. In one sequence, placebo spray is applied before the first capillary blood glucose measurement and vapocoolant spray is applied before the second measurement. In the other sequence, vapocoolant spray is applied before the first measurement and placebo spray is applied before the second. The second measurement is performed on the corresponding finger of the contralateral hand according to the assigned sequence. No additional punctures beyond those clinically indicated are performed.

Vapocoolant spray containing ethyl chloride is applied from a distance of 30 cm for 10 seconds before the procedure. The placebo consists of sterile water spray applied in the same manner. After spray application, the site is cleansed according to the standard protocol, the fingertip is punctured with a standard lancet, and capillary blood glucose measurement is performed using the study device.

The primary outcome is pain intensity during capillary blood glucose measurement, assessed immediately after each procedure using a 100 mm Visual Analog Scale. Secondary outcomes include adverse events related to spray application, such as pruritus, coolness, numbness, erythema, or burning sensation.

The crossover design allows each participant to serve as their own control, thereby reducing interindividual variability in pain perception. Randomization of intervention order is used to minimize potential sequence and acclimatization effects associated with repeated glucose measurements. The results of this study may support the use of a simple and practical analgesic strategy to improve patient comfort during routine capillary blood glucose testing in emergency department practice.

Inclusion Criteria:

• Patients aged ≥18 years
• Patients requiring at least two capillary blood glucose measurements for any reason
• Patients who agree to participate in the study

Exclusion Criteria:

• Allergy to the components of the spray
• Conditions that may affect capillary blood glucose measurement or pain perception, such as peripheral neuropathy or peripheral arterial disease
• Blood glucose levels outside the measurable range of the capillary device (extremely low or high levels)
• Cognitive disorders that prevent the evaluation of the Visual Analog Scale (VAS), such as dementia, Alzheimer's disease, or cerebrovascular diseases
• Severe conditions in other parts of the body that may interfere with pain evaluation

The random allocation sequence was generated by an investigator not involved in direct patient care. Participants were randomized into two sequence groups using an online randomization tool with block randomization. A fixed block size of four was used to ensure balanced allocation between groups. Following randomization, group assignments were placed in sequentially numbered, opaque, sealed envelopes.

To ensure blinding, both the vapocoolant spray and placebo containers were wrapped in opaque white paper to conceal their contents and labeled only as "1" or "2" according to the assigned sequence. Apart from these numerical labels, the containers were identical in appearance. This labeling procedure was performed by an individual who was not involved in patient care, outcome assessment, or data analysis. Thus, both participants and the care providers administering the spray remained blinded to the intervention type.