The results of this study demonstrate that the BIS may be a valid monitor of the depth of sedation for children undergoing dental restorations with mild to moderate sedation. The BIS values correlated significantly with the UMSS scores. The BIS has several potential advantages over observational clinical sedation scoring systems: it is objective, quantitative, easy to use, and free of observer bias, and does not require the use of stimuli that can result in patient responses that disrupt the procedure for which the child is sedated. These results are consistent with previous studies that validated the BIS against UMSS in sedated children.15,24
There has been only 1 other study utilizing the BIS for oral sedation of pediatric dental patients. Religa et al28
found an association between BIS values and behavior during oral sedations, using the AAPD sedation guidelines, which are a scale based on behavioral responsiveness to stimuli. Our study differs from this one in that we compared BIS values to a validated pediatric sedation scale, the UMSS. Also, in their study no baseline values for BIS were obtained, there was no blinding to the BIS data, and they did not correlate both instruments (BIS and AAPD sedation scale); they only associated the observed behaviors to the level of sedation according to the BIS value and AAPD sedation scale. Two other studies have analyzed BIS values to sedation scales in pediatric and adult patients undergoing oral surgery procedures. Overly et al29
compared BIS values to the OAA/S11
scales, both validated scales in pediatric dental patients undergoing oral surgery. Their sample was smaller (16 patients) but they had blinding and were able to obtain a repeated-measures regression analysis and found a positive correlation. Sandler and Sparks26
compared BIS values to OAA/S scores in 25 adult patients undergoing IV sedation for third molar extractions. They also found a positive correlation.
A problem in validating the BIS monitor as an assessment of sedation depth is the absence of a gold standard for comparison. A variety of clinical scoring systems exist and have been utilized in adults, but few have been validated in children. The UMSS has successfully been validated for measuring sedation depth in children.10
However, these scales are subject to interobserver variability, especially in the middle of the scale. This can explain the lack of significant difference with the repeated-measure analysis between the BIS values and UMSS 2 and 3, 2 and 4, and 3 and 4. In our study we also had 7 operators assigning the UMSS scores, which could have increased the variability. Interestingly, Malviya et al9
also compared the BIS to UMSS in pediatric patients and found a lack of correlation between the BIS and UMSS scores of 2 and 3. Comparisons between BIS and other observational tools have shown similar variability in the midranges of sedation.31,32
In our study there was also lack of correlation between the deeper levels of UMSS sedation scores and BIS values. This phenomenon can be explained by the relatively rare occurrence of the deeper levels of sedation (only 88 [19.3%] for UMSS 3 and 18 [4.0%] for UMSS 4 reported, which occurred to 16 patients and 3 patients respectively) with the use of sedative agents and doses that usually cause only mild to moderate sedation. Interestingly, there were 27 “deeply sedated” or “unarousable” observations where the BIS readings were in the “awake-alert” category.
Some clinical scoring systems have the disadvantage of requiring the application of additional verbal or noxious stimuli to assess the level of sedation during the procedure. Clinicians are reluctant to apply vigorous physical stimuli to children undergoing mild to moderate sedation for fear of the accompanying patient response of undesirable movements. However, the UMSS requires the repeated application of a uniform, quantifiable stimulus of the same intensity (light touch to face and arm). Standardizing the stimulus among the 7 operators is difficult and may have resulted in underestimating or overestimating the level of sedation. This also may have contributed to the lack of agreement between some of the sedation scales and the BIS values.
We were able to establish the validity of the BIS monitor by determining the construct validity of this instrument. The validity of the BIS value as a measure of sedation was supported by the decrease in BIS values after the administration of the sedative agent and the subsequent increase as the patient returned to baseline and was discharged.
Limitations of this study included the sample size, unequal distribution of patients for each different sedation regimen, variety of dental procedures performed, and different lengths of procedures, all of which could confound the results. For example, although we attempted to control for sedation regimen in our analysis because of the limited number of patients on 3 of the sedation regimens utilized, we had to combine the results for these in order to control for drug effect. This resulted in no difference in BIS values between the most commonly used regimen (chloral hydrate/meperidine/hydroxyzine) and the other 3 regimens. Further studies would be indicated to define the relationship between BIS values and each sedation regimen in a larger sample of patients. Additionally, the sedation regimens utilized were intended only for mild to moderate sedation; no conclusions could be obtained about the value of the BIS for deeper sedations. The use of the BIS monitor in deeper sedation could be established by studying the correlation of BIS values in pediatric dental patients undergoing IV sedation.
Known limitations of the BIS monitor include signal quality and electrical interference.17
A low signal-to-noise ratio is indicative of poor quality input into the monitor, and this can alter the readings. Additionally, the accuracy of the BIS scores can be affected by the electromyographic activity. A high electromyographic activity can be present in sedated patients, interfering with EEG signal acquisition and falsely elevating the BIS values. It is unknown what type of effect electromyographic activity, particularly on the temporalis muscle, has on the BIS values during dental or oral surgery procedures. Technically the BIS monitor can be somewhat difficult to use in children because some are uncomfortable with the amount of pressure needed to apply the monitor correctly. Religa et al28
in their study lost 33% of the data because of the difficulty in applying and getting usable information from the BIS monitor. We did not encounter as many problems with the use of the monitor in our patient population and were able to obtain data on all 35 enrolled subjects. Another shortcoming of the BIS monitor is that it has been observed to lag approximately 60 seconds behind the clinical situation,33,34
so that the reading reflects the level of consciousness about 60 seconds in the past.
Ongoing assessment of the depth of sedation is very important for early identification of the patient's progression into deep sedation and the potential loss of protective reflexes. The AAPD, American Academy of Pediatrics, and ASA guidelines require ongoing assessment of the depth of sedation throughout the procedure. The BIS monitor may provide and additional objective measure of sedation depth to ensure patient safety.