The required sample size for a rct to test the impact

The required sample size for a RCT to test the impact of an interven-
tion ( e.g. , brain function monitor) on the incidence of intraoperative
awareness is invariably large. The Task Force also recognizes that, with
low-incidence data, a difference in the recording of one or two cases
of intraoperative awareness can affect the statistical significance of
study findings.
Limiting the study to patient subgroups thought to have a higher risk
for intraoperative awareness ( e.g. , cardiac surgery, cesarean delivery,
emergency trauma surgery) may allow for a smaller sample size and
provide useful information regarding these subgroups. However, the
Task Force recognizes that the generalizability of these findings to the
larger population of general anesthesia patients may be limited.
Consensus-based Evidence
Consensus was obtained from multiple sources, including (1) survey
opinion from consultants who were selected based on their knowledge
or expertise in intraoperative awareness, (2) survey opinions from a
randomly selected sample of active members of the ASA, (3) testimony
from attendees of three open forums held at national anesthesia meet-
ings, (4) Internet commentary, and (5) Task Force opinion and inter-
pretation. The survey rate of return was 60% (n 57 of 95) for consultants
and 30% (n 151/500) for the ASA membership. Survey results are
presented in the text of the document and in tables 1 and 2.
Ninety-one percent of the consultants and 72% of the ASA members
indicated that they had personally used a brain function device in the
past. Fifty-seven percent of the consultants indicated that they make
use in their current practice of a brain function device always (11.1%),
frequently (20.4%), or sometimes (25.9%). Thirty-six percent of the ASA
members indicated that they make use in their current practice of a brain
function device always (6.0%), frequently (13.4%), or sometimes (16.8%).
The consultants were also asked to indicate which, if any, of the
evidence linkages would change their clinical practices if the Advisory
was instituted. The rate of return was 18% (n 17 of 95). The percent
of responding consultants expecting no change associated with each
linkage were as follows: preoperative evaluation—82%; informing pa-
tients of the possibility of intraoperative awareness—65%; check an-
esthesia delivery systems—94%; prophylactic use of benzodiazepines
as coenesthetics—100%; use of clinical techniques to monitor for
intraoperative awareness—94%; use of conventional monitoring sys-
tems to monitor for intraoperative awareness—100%; use of brain
function monitors to monitor for intraoperative awareness—59%; in-
traoperative use of benzodiazepines for unexpected consciousness—
100%; use of a structured interview for patients who report recall of
intraoperative events—41%; use of a questionnaire for patients who
report recall of intraoperative events—53%; and counseling for pa-
tients who report recall of intraoperative events—76%. Seventy-one
percent of the respondents indicated that the Advisory would have no
effect on the amount of time spent on a typical case. Four respondents