We report in this study that adjunctive boluses of remifentanil are not necessary to prevent acute pain in deeply sedated patient.
Protocolized optimized sedation and pain control in the intensive care unit (ICU) can help to reduce duration of mechanical ventilation and length of stay in ICU and hospital by reducing drug consumption
[4, 19]. However, it could be not sufficient to provide an adequate analgesia during an acute painful care. Indeed, Payen et al. described a rising of BPS during procedure in patient under correct level of sedation
. Optimization of analgesic control, by adjunctive therapy for example, could be needed to impair the risk of posttraumatic stress. Remifentanil, because of its pharmacologic properties could be a very interesting approach. This short-acting drug could protect the patient during procedure without increasing the risk of oversedation and consequences. In this study, we did not observe differences in the variation of BIS values, as a surrogate for analgesia evaluation, between the Remifentanil and placebo groups in mechanically ventilated, deeply sedated patients during a fiberoptic bronchoscopy. Moreover, BIS value did not change over time in both groups. We also do not observe significant difference between placebo and Remifentanil group according to PAM and heart rate. Heart rate is always higher in the placebo group than in the remifentanil one, which could be explained by direct chronotropic negative effect of Remifentanil. The absence of BIS variation observed during the procedure could be explained by different ways. The very low values recorded at the beginning of the procedure can limit the impact of adjunctive therapy. Indeed, we choose to study a particular group of patients needing deep sedation for procedure. We may hypothesize that deep sedation conducted to low initial BIS value, leading to blunt significant variation in BIS value. Statistically, an expected decrease in BIS value of 50 %, used in anterior studies, is probably overestimated in this particular setting of deep sedated patients, and the sample size could be underevaluated. Tolerance to fentanyl developed before the procedure could limit the interpretation of results, but length of sedation before procedure was short and dose was controlled by pain scale. Furthermore, no signs of opioids tolerance were developed by patients. We can also hypothesize that the level of pain is not sufficient but previous study described fiberoptic examination as one of the most painful procedure
. Remifentanil doses could not be enough efficient, but the absence of BIS variation in the placebo group is not in accordance with this hypothesis.
In particular, critically ill conditions, such as patients with brain trauma or respiratory failure, or for care procedure (fiberoptic bronchoscopy, tracheotomy…), neuromuscular blocking agents administration is recommended making the use of sedation scale scores, such as the Behavioral Pain Scale (BPS)
, impossible. Bispectral Index, developed initially to monitor depth of anesthesia in the operating room
[13, 20, 21], could be an approach. In an experimental study of healthy volunteers, adjunctive opioids to volatile agents-based anesthesia increases clinical sedation but has no impact on BIS value. However, patients did not suffer from acute painful procedure
. In ICU, BIS use remains controversial because of the high level of variability of this parameter as described in our study (Figure
4), which led us to study the variation of this rather isolated value. Some authors have concluded that the most recent version of BIS—BIS XP—is useful in the ICU setting for assessing sedation
, whereas others do not share this view
. The use of BIS monitoring to assess pain in our study could be criticized, but it was shown to be sensitive to nociceptive stimuli in critically ill, sedated patients
[6, 25]. Brocas et al. were able to blunt BIS variations by adding a bolus of a short-acting opioid to sedated patients before endotracheal suction. Other studies have described similar results with other opioids
. In accordance with these results, and with the proposition of French consensus on sedation in the ICU, we decided to use this device to evaluate the level of pain of our critically ill patients