An initial investigation of bispectral monitoring as an adjunct to nurse-administered propofol sedation for colonoscopy.

BACKGROUND AND AIMS

Bispectral (BIS) monitoring has been used to evaluate depth of sedation in intensive care and surgical patients. We sought to explore its utility as a monitoring device for nurse-administered propofol sedation (NAPS) during colonoscopy.

METHODS

Fifty consecutive patients (ASA I or II) receiving NAPS for outpatient colonoscopy were evaluated. BIS scores, sedation scores, and propofol dosing were correlated. The nurses assessed the usefulness of BIS by questionnaire.

RESULTS

The mean (SD) dose of propofol required to produce a BIS value </= 60 was 109.4 (43.9) mg and an Observer's Assessment of Alertness/Sedation (OAA/S) score of 1 (deep sedation) was 91.4 (44.8) mg (p < 0.0001). The mean times required to achieve BIS values </= 60 (188 +/- 147.1 s) and </= 70 (164.3 +/- 95.1 s) were significantly longer than the mean time required to achieve an OAA/S of 1 (117.4 +/- 93.0 s, p= 0.0007). Similarly, during the recovery phase, there was a lag time of 197.9 s between mean (SD) time required from the last dose of propofol to an OAA/S of 5 (372.1 +/- 197.1 s) and the mean (SD) time required from the last dose of propofol to a BIS value >/= 90 or return to baseline (570 +/- 279.9 s, p < 0.0001). The mean (SD) BIS value in the maintenance phase of sedation was 58.9 (8.53), with a range of 22-88. Nurses administering propofol rated the usefulness of BIS at a mean of 2.85 (maximum usefulness scored as 4) in guiding the dosing of propofol sedation during the maintenance phase of sedation. No patient required mask ventilation or endotracheal intubation.

CONCLUSIONS

The BIS index in its current version is not useful in titrating boluses of propofol to an adequate level of sedation, because there is a substantial lag time between decrease of BIS scores to <70 and OAA/S scores indicative of deep sedation. There is also a substantial lag time between recovery of alertness and return of BIS scores to normal. A controlled trial of whether BIS values can assist in avoiding unnecessary propofol dosing during the maintenance phase of sedation appears warranted.