Wang 2019.

Study characteristics
Methods	Study design: randomised controlled trial, parallel arm Setting: single‐centre trial at a provincial hospital affiliated to Shandong University, China Study start/end dates or study duration: between July 2018 and April 2019 Funding sources: Cardiovascular Multidisciplinary Integrated Research Fund, the Natural Science Foundation of Shandong Province, the Clinical Science and Technology Innovation Program of Jinan City, and the Medicine and Health Science Technology Development of Shandong Province Declarations of interest: "The authors declare that they have no competing interests."
Participants	Sample size: 187 Patient age: levosimendan group median 5 months (IQR 2 to 11 months), placebo group median 7 months (IQR 2 to 16 months) Patient sex: levosimendan group 42/94 females, placebo group 41/93 females Diagnosis/severity: RACHS score 2‐5 Inclusion criteria: children up to 48 months of age undergoing cardiac surgery with use of cardiopulmonary bypass
Interventions	Intervention: continuous infusion of 0.05 μg/kg/min levosimendan, adjusting infusion rate according to adverse events. Infusion was started as quickly as possible following surgery, for 48 hours. Control: placebo with same infusion appearance, rate, and duration as in the levosimendan group Co‐interventions: any additional medications as appropriate, only concomitant nesiritide not permitted
Outcomes	Primary outcome: LCOS incidence. "LCOS was defined as two consecutive measurements of low cardiac output (defined as a cardiac output of≤2.2L/min/m2, without associated relative hypovolaemia), one measurement of low cardiac output plus the use of two or more inotropes at or beyond 24 h after surgery, or the use of two or more inotropes at or beyond 24 hafter surgery with the indicated reason being low cardiac output." Secondary outcome(s) Mortality and rehospitalisation within 90 days post‐surgery Duration of mechanical ventilation Durations of ICU and hospital stay Incidences of postoperative complications Myocardial enzymology at 24,48, 72, and 96 h post‐surgery Invasive haemodynamic parameters at 24, 48, and 72 h post‐surgery Vasoactive inotropic score at 2,24, 48, and 72 h post‐surgery Post‐surgical safety outcomes including hypotension, arrhythmia, and hepatorenal function (pre‐defined acute kidney injury and incidence of renal replacement therapy ("acute renal injury necessitating dialysis", p 3) Follow‐up period: 90 days
Notes	Intention to treat analysis: yes, after randomisation Trialists contacted: yes Unpublished information received: no
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"A computer‐generated, permuted block sequence stratified according to the trial center was used to support the study randomization"
Allocation concealment (selection bias)	Low risk	"Sequentially numbered opaque envelopes containing participant assignment groups were sealed"
Blinding of participants and personnel (performance bias) All outcomes	Low risk	All physicians, patients, outcome assessors, and research staff were blinded to patient treatment assignments, and "preparations being prepared by dedicated trial personnel such that patients and physicians were unaware of which treatment" a given patient received. Detailed description of placebo preparation provided.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	“Sequentially numbered opaque envelopes containing participant assignment groups were sealed, with all physicians, patients, outcome assessors, and research staff being blinded to the patient treatment assignments”
Incomplete outcome data (attrition bias) All outcomes	Low risk	No incomplete outcome data suspected.
Selective reporting (reporting bias)	Low risk	Drug infusion periods shorter than per protocol are reported in detail.
Other bias	Low risk	No other bias suspected. “Patients treated in this trial purchased the drug at full cost, and trial design, data collection, subsequent analyses, and manuscript submission were not influenced by the drug manufacturer or the funding agencies supporting this trial”.

AET: atrial ectopic tachycardia; AKH: Allgemeines Krankenhaus der Stadt; ALF: is the abbreviation in Swedish of an agreement between central government and seven regions on physician education and clinical research; AV: atrioventricular; BNP: brain natriuretic peptide; CBP: cardiopulmonary bypass; CICU: cardiac intensive care unit; CRO: clinical research organisation; DPB: diastolic blood pressure; ECMO: extracorporeal membrane oxygenation; h: hour; HD: high dose; hr(s): heart rate; ICU: intensive care unit; IQR: interquartile range; JET: junctional ectopic tachycardia; LCOS: low cardiac output syndrome; LD: low dose; LVFS: left ventricular fraction of shortening; LVIS: levosimendan vasoactive‐inotropic score; min: minimum; MCS: mechanical circulatory support; p: page; RACHS: risk‐adjusted classification for congenital heart surgery; SBP: systolic blood pressure; SICU: surgical intensive care unit; SVT: supraventricular tachycardia; UOP: urine output; VIS: vasoactive inotropic score; vs: versus; yr: year