B-Type Natriuretic Peptide and Hemoglobin are Two Major Factors Significantly Associated With Baseline Cerebral Oxygen Saturation Measured Using the INVOS Oximeter in Patients Undergoing Off-Pump Coronary Artery Bypass Graft Surgery

Objectives: To investigate an association between the preoperative plasma B-type natriuretic peptide (BNP) concentration and cerebral regional saturation (rSO₂) measured using the INVOS oximeter (Medtronic, Minneapolis, MN).

Design: A retrospective data analysis.

Setting: Single university hospital.

Participants: Patients undergoing off-pump coronary artery bypass (OPCAB) surgery.

Interventions: None.

Measurements and main results: Associations of variables obtained from preoperative blood laboratory tests and transthoracic echocardiography with baseline rSO₂ before induction of general anesthesia were investigated using bivariate and multivariate regression analyses in 330 OPCAB patients. With bivariate analyses, age; body size-related variables such as weight and body surface area; hematologic function-related variables such as blood hemoglobin (Hb) concentration and arterial oxygen saturation; renal function-related variables including estimated glomerular filtration rate, creatinine, and blood urea nitrogen; hepatic function-related variables including cholinesterase, albumin, total bilirubin, and alanine aminotransferase; serum electrolytes including sodium, chloride, and phosphorus; BNP or log-transformed BNP; and 13 transthoracic echocardiography variables such as left ventricular ejection fraction highly significantly correlated with baseline rSO₂ (p < 0.0001). However, the multiple regression analysis revealed that only BNP and Hb remained major factors significantly associated with baseline rSO₂ (p < 0.0001), while estimated glomerular filtration rate, arterial oxygen saturation, and body surface area remained minor factors (p < 0.05). Baseline rSO₂ correlated better with log-transformed BNP than with BNP, indicating that rSO₂ correlated with BNP in an exponential fashion.

Conclusions: Preoperative BNP and Hb concentrations were 2 major factors associated with INVOS rSO₂ in patients undergoing OPCAB.