Prognostic Significance of Low Serum Cholesterol after Cardiothoracic Surgery

BACKGROUND: The precise prognostic significance of critically low cholesterol concentrations in patients undergoing cardiothoracic surgery is unknown. METHODS: In a retrospective case-control study, we analyzed the database of 2074 patients, of whom 87 died postoperatively in hospital. All patients underwent cardiothoracic surgery using a heart-lung machine. Age, sex, body mass index, preoperative ejection fraction, smoking, diabetes mellitus, type of operation, emergency surgery, renal deficiency, pulmonary hypertension, and endocarditis were considered together with serum concentrations of cholesterol, C-reactive protein, alanine aminotransferase, and triglycerides. The statistics included sensitivity, specificity, predictive value, odds ratio, and the ROC curve. RESULTS: Cholesterol decreased sharply immediately after surgery in both the deceased and the survivors. In the deceased, the mean cholesterol concentration (+/- SE) remained rather low between days 4 and 7 after surgery [2.46 +/- 0.16 mmol/L (95 +/- 6 mg/dL)]. In the survivors at that time, the mean cholesterol concentration was significantly (P <0.001) higher [4.37 +/- 0.03 mmol/L (169 +/- 1 mg/dL)]. The positive predictive value of a critically low cholesterol concentration [<3.10 mmol/L (<120 mg/dL)] was 25.4%, increasing to 66.6% at a cutoff value of 1.55 mmol/L (60 mg/dL). The odds ratio under those circumstances was 15.5, and the area under curve (C-statistic) was 0.90. CONCLUSIONS: The cholesterol concentration between days 4 and 7 after cardiothoracic surgery possesses a high prognostic significance in terms of in-hospital mortality.