High postoperative serum cortisol level is associated with increased risk of cognitive dysfunction early after coronary artery bypass graft surgery: a prospective cohort study

Abstract

Context: Stress response induced by surgery is proposed to play an important role in the pathogenesis of postoperative cognitive dysfunction.

Objective: To investigate the association between postoperative serum cortisol level and occurrence of cognitive dysfunction early after coronary artery bypass graft surgery.

Design: Prospective cohort study.

Setting: Two teaching hospitals.

Patients: One hundred and sixth-six adult patients who were referred to elective coronary artery bypass graft surgery from March 2008 to December 2009.

Intervention: None.

Main outcome measures: Neuropsychological tests were completed one day before and seven days after surgery. Cognitive dysfunction was defined using the same definition as used in the ISPOCD1-study. Blood samples were obtained in the first postoperative morning for measurement of serum cortisol concentration. Multivariate Logistic regression analyses were performed to assess the relationship between serum cortisol level and occurrence of postoperative cognitive dysfunction.

Results: Cognitive dysfunction occurred in 39.8% (66 of 166) of patients seven days after surgery. Multivariate Logistic regression analysis showed that high serum cortisol level was significantly associated with the occurrence of postoperative cognitive dysfunction (odds ratio [OR] 2.603, 95% confidence interval [CI] 1.371-4.944, P = 0.003). Other independent predictors of early postoperative cognitive dysfunction included high preoperative New York Heart Association functional class (OR 0.402, 95% CI 0.207-0.782, P = 0.007), poor preoperative Grooved Pegboard test score of nondominant hand (OR 1.022, 95% CI 1.003-1.040, P = 0.020), use of penehyclidine as premedication (OR 2.565, 95% CI 1.109-5.933, P = 0.028), and occurrence of complications within seven days after surgery (OR 2.677, 95% CI 1.201-5.963, P = 0.016).

Conclusions: High serum cortisol level in the first postoperative morning was associated with increased risk of cognitive dysfunction seven days after coronary artery bypass graft surgery.

Figure 1. Flow chart of the study.

LVEF = left ventricular ejection fraction.

Figure 2. Relationship between the serum cortisol level and the incidence of cognitive dysfunction seven days after coronary artery bypass graft surgery.

Patients with an elevated serum cortisol level had a significantly higher incidence of postoperative cognitive dysfunction (P < 0.001). The normal range of serum cortisol concentration is 138 to 690 nmol L^-1. Level 1 indicates a serum cortisol concentration of less than 138 nmol L^-1, level 2 between 138 and 690 nmol L^-1, and level 3 of greater than 690 nmol L^-1.