For many years, total knee arthroplasty (TKA) has been a common and effective procedure to treat chronic refractory joint pain. With a worldwide aging population, as well as a rising rate of obesity and related osteoarthritis, the utilization of TKA has considerably expanded over time, and this increase is expected to continue. Accordingly, healthcare systems are exploring various strategies to address this growing demand, while ensuring efficiency, cost-effectiveness and safety. Among these approaches, and based on several reports comparing the risks and benefits of general and regional anesthesia, a first attempt has been made to switch from performing TKAs under general to spinal anesthesia. Although efforts must be pursued, as general anesthesia remains the main tendency for TKA, results regarding spinal anesthesia are extremely encouraging. As such, spinal anesthesia has been associated with a decreased rate of complications, including wound infection, blood transfusions or mortality, and with reduced length of surgery and hospital stay.

Yet, while spinal anesthesia prevents procedural pain and ensures immobility of the operative territory, the patient is still awake, conscious of all the noises in the operating room, and can have a high level of intraoperative anxiety. Currently, the standard of care to manage procedural anxiety is pharmacological sedation; i.e. the intravenous administration of additional anesthetic agents such as propofol or midazolam. However, pharmacological sedation has considerable undesirable side effects. Hence, risks of intraprocedural adverse events including respiratory depression, hemodynamic perturbations, or paradoxical effects such as hostility, aggression, and psychomotor agitation, are increased. Moreover, it might lead to longer procedure duration or time to discharge, slower recovery, and postoperative delirium or cognitive dysfunction. In addition to these challenges, it becomes clear that procedural sedation directly impacts consumption of drugs such as opioids, triggering the highlighted risk of addiction.

In this context, new international guidelines for risk mitigation in pharmacological sedation have emerged. Both American and European anesthesia societies recommend particular caution in the use of sedative drugs, especially with benzodiazepines and in patients with obesity or obstructive sleep apnea, which are highly comorbid with knee osteoarthritis. However, only providing less, or even no sedatives at all, is not a valuable solution, as it would negatively impact patient comfort and satisfaction and negatively affect clinical workflow. Therefore, alternative, non-pharmacological interventions that would be able to reduce drug requirements and associated risks while ensuring a similar patient experience are being actively sought.

Among those approaches, there is currently a growing interest towards clinical hypnosis, a one-to-one delivered technique inducing "A state of consciousness involving focused attention and reduced peripheral awareness characterized by an enhanced capacity for response to suggestion". The hypnotic state involves the capacities of absorption (tendency to be fully involved in a mental experience), dissociation (a mental separation from the environment), and suggestibility (tendency to comply with hypnotic suggestions). When combined during surgery with conscious IV sedation and local or regional anesthesia, forming the so-called hypnosedation, clinical hypnosis is associated with improved perioperative safety and comfort as well as better clinical outcomes. More precisely, the use of clinical hypnosis during medical procedures has been shown to reduce pain, emotional distress and anxiety while preserving consciousness, spontaneous breathing, reflexes as well as hemodynamic and metabolic changes, to decrease the time spent in the operating room, and to have a beneficial impact on immediate recovery, characterized by reduced fatigue and postoperative nausea and vomiting (PONV). Furthermore, this technique allows to significantly reduce the administrated doses of IV sedation and the associated costs. Yet, several obstacles limit the use of hypnosedation as a standard of care in the operating/ procedure room: the need for continuous patient-side presence of trained professionals in the room (and the cost related to the mobilization of these professionals), the small number of cases per day one healthcare provider can handle, patient's language proficiency, as well as the heterogeneity of the responses to the hypnotic suggestions of patients themselves.

To overcome those limitations, Oncomfort has created Digital Sedation™ sessions, classified as Software as a Medical Device (SaMD), allowing to deliver clinical hypnosis - together with additional integrative therapeutic approaches - through virtual reality, a technique called Virtual Reality Hypnosis (VRH). Virtual reality (VR) is "a computer-generated simulation of a lifelike environment that can be interacted with in a seemingly real or physical way by a person, by means of responsive hardware such as a visor with screen or gloves with sensors. In the medical field, VR has been used as a non-pharmacological mean to alleviate pain, anxiety, and general discomfort during uncomfortable procedures. VR is thought to work by distracting patients from uncomfortable procedures: by giving the illusion of really going into the artificial world, VR is able to capture patient's attention away from the real environment. Accordingly, VR could strengthen the level of absorption and dissociation induced by clinical hypnosis, especially in low hypnotizable persons. Hence, VRH technology allows to deliver clinical hypnosis - and its related benefits- to a considerably greater number of patients. This automated way of delivering hypnosis responds to most of the limitations of the use of clinical hypnosis mentioned supra (e.g. availability of trained staff, language barrier,...).

To date, the Oncomfort's Digital Sedation™ is used in more than 100 hospitals, and more than 80 000 patients have already beneficiated from this type of VRH in daily clinical practice (e.g. interventional radiology, oncology, surgery,...). In line with its intended use, first studies have demonstrated that Digital Sedation™ reduces both experimental and clinical pain, as well as procedural anxiety. In addition, preliminary results indicate that it might replace midazolam during endoscopic urologic surgery, avoiding the respiratory side effects associated with pharmacological sedation. Over the last year, at the CHU of Liège, Digital Sedation™ has been offered to patients during orthopedic surgeries, demonstrating the feasibility of using VRH during TKAs performed under spinal anesthesia. While results seem to be positive in terms of performance of the procedure and patient satisfaction, the potential beneficial impact of this solution has not been systematically addressed yet. The goal of the present study is to objectify those effects, and in particular, to determine whether VRH can replace - at least in part- the intraoperative administration of midazolam, allowing to avoid its associated side effects while ensuring a similar patient's comfort.