The management of acute pain and anxiety related to healthcare interventions remains a major challenge, especially in the intensive care unit (ICU). Pain is common in critically ill adults at rest and during procedures including regular activities (e.g., turning) and discrete procedures (e.g., arterial catheter insertion). Chest tube removal, wound drain removal, and arterial line insertion were described to be the three most painful procedures, with median pain scores of 5 (3–7), 4.5 (2–7), and 4 (2–6) on a 0–10 numeric rating scale, respectively .
Following cardiac surgery, mediastinal and pleural chest tubes are inserted to drain blood, then removed typically during the second postoperative day. This withdrawal is described by patients and nurses as a painful and frightening experience , and a source of anxiety, especially with regard to fear of pain. After cardiac surgery, 1 week after discharge from ICU, 82% of patients reported pain as the most common traumatic memory of their ICU stay and 6 months later, 38% still recalled pain as their most traumatic ICU memory . Many treatments have been proposed, including analgesics, morphinics, nonsteroidal anti-inflammatory drugs, inhaled nitrous oxide and subcutaneous infiltration of local anaesthetics, such as lidocaine or bupivacaine [4,5,6]. However, the absence of any treatment is also frequent, given the brevity of the procedure.
An equimolar mixture of oxygen and nitrous oxide (Kalinox®) has been proposed in the management of many anxiogenic and painful situations and was effective in providing analgesia [7,8,9]. It has been proposed for the ablation of mediastinal redons after cardiac surgery .
Virtual reality (VR) is a recent technology that allows the representation of a pleasant environment in three dimensions with complete immersion for the patient, using a helmet. The video quality achieved by this technology and its growing accessibility have attracted the medical community to integrate it into the therapeutic arsenal available to improve the patients’ satisfaction. By distracting patients, this technology helps to reduce anxiety, discomfort and, ultimately, painful feelings related to care . A recent meta-analysis of 20 randomized studies showed a beneficial effect of VR, with a 50% reduction in pain scores . These data suggest that VR might have a role in acutely painful procedures. However, current available studies are clinically and statistically heterogeneous.
The most common scale used for pain or/and anxiety in conscious patients in the ICU is the numeric rating scale (NRS), which is a self-reported scale of feeling, graduated from 0 to 10. This scale is simple, widely used, and easily understood by patients. Analgesic protocols were created to titrate the treatment according to the patient felt pain . In awake patients, current guidelines for prevention and management of pain in ICU recommend the use of self-report scale for pain assessment. Guidelines also suggest that other technology including these measuring HR variabilities, may be of interest in the ICU pain assessment process and should be explored. Although NRS still remains the recommended method in patients able to communicate, electrophysiological tools, not based on patient’s feeling, have been developed to evaluate pain .
The analgesia/nociception index (ANI) monitor is a device that collects continuously the patient’s electrocardiogram signal from the scope. The ANI value is based on the influence of the respiratory cycle on the RR interval. It allows a measurement of the heart rate variability, modulated by the parasympathetic nervous system and the sympathetic central nervous system at the sinoatrial node . The ANI monitor gives three values of ANI. A continuous index is displayed (each basic measurement is performed on 64 s of data with a sliding window every second); then, a calculation is made every second and averaged over two time periods: a short average ANIi (average over 2 min) and a longer average ANIm (average over 4 min).
A mathematic analysis is made by the monitor to normalize the ANI values between 0 (maximum sympathetic effect, indicating the highest level of stress) and 100 (maximum parasympathetic effect, indicating a low level of stress) . In other words, higher ANI values would typically be associated with lower pain scores. It has been demonstrated that the ANI is useful to guide analgesic titration during surgery , to evaluate postoperative pain  and emotional status . When used in routine care procedures in critically ill non-comatose patients, ANI values were significantly correlated with Behavioral Pain Scales and instant ANI ≥ 43 had a negative-predictive value of 90% for excluding significant pain . In another study, in the immediate postoperative context in conscient patients but before tracheal extubation, the sensitivity and specificity of ANI < 50 to discriminate between patients with NRS ≤ 3 and NRS > 3 were both 86%, giving a 92% negative predictive value, and an area under the ROC curve of 0.89 .
This study aimed to compare VR vs. Kalinox® for pain and anxiety management during the removal of chest drains after cardiac surgery, based on ANI values.