Low Serum Sodium Level during Cardiopulmonary Bypass Predicts Increased Risk of Postoperative Stroke after Coronary Artery Bypass Graft Surgery
OBJECTIVE:
Rapid decreases in serum sodium levels are associated with altered mental status, seizures, and coma. During cardiac surgery,
serum sodium levels decrease rapidly when cardiopulmonary bypass is
initiated because cardiopulmonary bypass causes hemodilution. However,
whether this decrease influences neurologic outcome after cardiac surgery
remains unclear. We investigated whether the average serum sodium level
during cardiopulmonary bypass is independently predictive of
postoperative stroke or 30-day all-cause mortality in patients who
undergo primary coronary artery bypass grafting.
METHODS:
In
a single-institution, retrospective cohort of 2348 consecutive patients
who underwent primary, isolated coronary artery bypass grafting,
sequential multivariate logistic regression was performed to determine
the threshold below which the average serum sodium level during
cardiopulmonary bypass independently predicts postoperative stroke or
early death. To further test the validity of this threshold and to
control for selection bias, stepwise multivariate logistic regression
was also performed on propensity score-matched patients (n = 924).
RESULTS:
An
average serum sodium level less than 130 mEq/L during cardiopulmonary
bypass was independently predictive of stroke, both in the entire study
cohort (1.44% vs 2.92%; odds ratio, 2.09; 95% confidence interval,
1.1-4.1; P = .03) and in the propensity-matched patients (0.9% vs 3.0%;
odds ratio, 4.1; 95% confidence interval, 1.3-13.0; P = .02). The
average serum sodium level during cardiopulmonary bypass was not
independently associated with early death, regardless of what threshold
value was used.
CONCLUSIONS:
An average serum sodium
level of less than 130 mEq/L during cardiopulmonary bypass is
independently associated with an increased risk of postoperative stroke
in patients who undergo primary coronary artery bypass grafting.
