The calcium sensitizer levosimendan has anti-ischaemic effects mediated via the opening of sarcolemmal and mitochondrial ATP-sensitive potassium channels. These properties suggest potential application in clinical situations where cardioprotection would be beneficial, such as cardiac surgery. We thus decided to investigate whether pharmacological pre-treatment with levosimendan reduces intensive care unit (ICU) length of stay in patients undergoing elective myocardial revascularization under cardiopulmonary bypass. One hundred and six patients undergoing elective coronary artery bypass grafting were randomly assigned in a double-blind manner to receive levosimendan or placebo. Levosimendan (24 microg kg(-1)) or placebo was administered as a slow i.v. bolus over a 10 min period before the initiation of bypass. Tracheal intubation time and the length of ICU stay were significantly reduced in the levosimendan group (P<0.01). The number of patients needing inotropic support for >12 h was significantly higher in the control group (18.0% vs 3.8%; P=0.021). Compared with control patients, levosimendan-treated patients had lower postoperative troponin I concentrations (P<0.0001) and a higher cardiac power index (P<0.0001). Pre-treatment with levosimendan in patients undergoing surgical myocardial revascularization resulted in less myocardial injury, a reduction in tracheal intubation time, less requirement for inotropic support, and a shorter length of ICU stay.