A medical or surgical emergency is a stressful life event. An emergency department is also a noisy and sometimes chaotic environment, contributing in itself to increase the anxiety related to the primary cause of the emergency consultation. Some common medical procedures, such as placing an intravenous catheter, may not only induce pain, but may exacerbate patients' anxiety or pre-existing pain. The well-being of patients, especially during invasive medical procedures, can however be improved by various communication techniques. However, the medical literature and clinical observation have shown that negative words are traditionally used to warn patients of an impending painful stimulus. However, contrary to common beliefs and practices, this type of warning can increase pain and anxiety. Using words with negative emotional content has an even greater impact than the positive impact of using words with positive emotional content. However, studies that have explored the impact of such messages suffer from two limitations: first, they were not conducted in the context of emergency department, and second, the effect attributable to healthcare providers themselves was not studied. However, healthcare providers who deliver a message with a positive or negative content in the context of a study are not blinded to message, therefore are aware of the arm of the intervention. This lack of double-blinding may introduces a bias, namely that the benefit of a positive message can be linked to healthcare providers and their global interaction with patients, and not just to verbal content. of the message. It is indeed possible that the caregivers, in a more or less conscious way, add in their communication elements congruent with the message studied, whether in the field of verbal or nonverbal communication (tone of voice, warmth, empathy , etc.).

The purpose of this study is therefore to investigate whether the modulation of information relating to the setting up of a CIP in emergencies has an impact on patients' pain and their level of anxiety. It also seeks to determine if this effect is comparable, whether the message is delivered by a standardized audio recording or by caregivers. Finally, it aims to explore whether there are differences in the assessment of pain and anxiety made by patients and that made by caregivers.

Statistical analysis will be realized using the Stata software, version 14 (StataCorp, Tx, USA). Descriptive data will be presented by mean and standard deviation, median and interquartile space or proportions regarding continuous gaussian, non-gaussian and categorical variables. Comparison between randomized groups will be done by using non paired Student t-test or Wilcoxon rank sum test regarding continuous variables, and by Chi2 test or Fisher exact regarding categorical variables, according to what is appropriate.

This study aims to demonstrate the superiority of an informative message with positive content over pain perception during intravenous cannulation. Statistical power is set at 80% to prove a difference, with alpha threshold at 0.05. Mean pain intensity is estimated at 34 mm on a Visual Analog Scale (possible intensity from 0 to 100 mm), with an estimated standard deviation at 24 mm. To detect the smallest clinically significative decrease in pain intensity (13 mm) caused by the intervention, a sample of 110 patients, that is 55 patients per group, is needed. Taking missing data or post-randomization patient withdrawal (estimated at 10%) into account, 60 patients will be randomized per group. A minimum of 240 patients in total for the two phases (that is the four arms of the study) will be needed to be enrolled.