Preoperative BNP levels may be better
predictor of complications after bypass surgery than postoperative levels
Results from a clinical study presented at the 2009 American
Society of Anesthesiologists (ASA) Meeting suggest that elevated preoperative
levels of the B-type natriuretic peptide (BNP) biomarker may predict hospital
length of stay and mortality after primary coronary artery bypass graft surgery
better than measurements of elevated postoperative BNP levels.
In the study, 1183 patients undergoing primary coronary
artery bypass graft (CABG) surgery were tested for elevated preoperative and postoperative
levels of a biomarker in their blood called B-type naturietic peptide. BNP is
an established heart failure biomarker that is secreted primarily by the ventricular
chambers of the heart when they are stretched. Previous research has shown that
elevated BNP levels pre-surgery can predict increased adverse events, including
death, after heart surgery.
"This study was designed to examine the potential prognostic
value of assessing postoperative BNP concentrations in the cardiac surgery population,
particularly with regards to what these postoperative levels may add to what can
already be predicted using preoperative BNP levels. This is an important question,
as factors that occur during and immediately after surgery can also contribute
to adverse outcomes after CABG surgery and may be reflected by elevated postoperative
BNP measurements," said Amanda A. Fox, M.D., lead author of the study and Assistant
Professor of Anesthesiology, Perioperative and Pain Medicine at Brigham and Women's
Hospital. "We took the approach of simultaneously assessing the value of preoperative
and postoperative BNP measurements to see what postoperative BNP can add to what
is already known from preoperative BNP and clinical risk factors for perioperative
risk stratification."
This study was a prospective longitudinal study of 1,183
patients undergoing primary coronary artery bypass graft surgery at Brigham and
Women's Hospital in Boston, MA and at the Texas Heart Institute, Baylor College
of Medicine, Houston, TX.
Mortality was defined as all deaths within five years
after surgery. Subjects were followed for a minimum duration of just over two
years after surgery with an average follow-up of about four years. During this
follow-up period after coronary artery bypass surgery, 115 deaths (9.7 percent)
occurred in the patients being studied.
After statistical analysis, researchers determined that
preoperative BNP remained an independent predictor of hospital length of stay
and approached being an independent predictor of mortality after clinical risk
factors and postoperative BNP were statistically accounted for. If considered
separately along with important clinical risk factors, both preoperative BNP and
postoperative BNP were independent predictors of the two studied outcomes.
"Our results suggest that when preoperative and postoperative
BNP measurements are considered together along with clinical risk factors for
negative outcomes after CABG surgery, preoperative BNP appears to be the more
reliable predictor of longer hospital stay and all-cause mortality. However, it
may be that when cardiac specific outcomes such as development of longer term
postoperative heart failure are assessed in future studies, postoperative BNP
will be better able to capture the likelihood of developing those events," said
Dr. Fox. "We believe that such future investigation is warranted. What our present
findings suggest is that preoperative BNP remains a good risk stratification tool
for hospital length of stay and all-cause mortality in primary CABG patients,
even when postoperative BNP is also considered as a risk stratification tool."
|