Table 1.

PICOS approach for selecting clinical studies in the systematic search

PICOS	Criteria
1. Participants	High-risk patients undergoing cardiac surgery, defined by preoperative severely depressed LVEF (<35%) and/or intra-/postoperative LCOS
2. Intervention	Levosimendan
3. Comparison	Placebo
4. Outcomes	Primary outcomes: mortality at longest follow-up, need for RRT Secondary outcomes: myocardial injury, supraventricular arrhythmias, acute kidney injury (risk, injury, or failure according to RIFLE criteria), duration of mechanical ventilation, development of LCOS (only for studies on preoperative severely depressed LVEF patients), intensive care unit and hospital lengths of stay, adverse events, or hypotension during drug infusion
5. Study design	Randomized controlled trials

Abbreviations: LVEF Left ventricular ejection fraction, LCOS Low cardiac output syndrome, RIFLE Risk, injury, failure; loss, end-stage renal disease, RRT Renal replacement therapy, PICOS Population, intervention, comparison, outcomes, and study design