Swindell 2007.

Methods	Type of study: parallel RCT Type of publication: full Setting: Birmingham Children's Hospital, Birmingham, UK Number of centres: 1 Dates (start and end): January 2005 to May 2006 Follow‐up: not stated but measurements taken intraoperatively Number of patients randomised: 11 in each group Number of patients analysed (primary outcome): 11 in each group
Participants	Inclusion: infants (< 1 year old) and neonates undergoing CPB for complex congenital heart surgery Diagnoses were hypoplastic left heart syndrome (12 patients), multiple complex defects (5 patients), transposition of the great arteries (3 patients), pulmonary atresia and ventricular septal defect (1 patient), hypoplastic aortic arch (1 patient). The operations they underwent were modified Norwood Stage 1 (12 patients), cavo‐pulmonary shunt (4 patients), arterial switch (3 patients), aortic arch repair (2 patients), pulmonary atresia repair (1 patient) Age: washed group: mean 45 days (range 1 to 180); unwashed group: mean 62 days (range 2 to 300) Weight: washed group: mean 4.2 kg (range 2.62 to 8.2); unwashed group: mean 4.0 kg (range 2.4 to 8.3) Gender (M/F): 12/10 Exclusion: not reported Statistically significant baseline imbalances between groups: not stated but control group have a higher mean age: 62 days versus 45 days
Interventions	2 groups: unwashed and washed All patients in the study received irradiated red cells as they had, or were suspected to have had, a syndrome associated with immunodeficiency as stated in the transfusion guidelines for Birmingham Children's Hospital Intervention arm: washed received the processed volume from 2 units of irradiated pre‐washed in a cell‐saver before addition to the CPB circuit prime. They received 2 units to compensate for the volume loss during processing Comparator arm: unwashed received 1 unit of unwashed irradiated red cells in the CPB circuit prime. They also received a second unit of unwashed irradiated red cells as required during CPB
Outcomes	Primary: potassium and lactate levels in the irradiated red cells and inpatient samples Other outcomes: sodium concentrations Samples were taken before addition to the prime (for the intervention group this meant pre and post washing), after connection of lines and 5 minutes of re‐circulation in bypass prime, from patient arterial blood prior to bypass, bypass circuit sample after start of bypass, at 28°C during cooling then re‐warming, then at 36°C after re‐warming. A final sample was taken from patient arterial blood immediately after bypass and clamping of arterial cannula
Notes	Funding: not reported Study objective: the study aimed to identify whether cell‐saver washing of irradiated red cells prior to transfusion reduced potassium and lactate levels in the donor blood. In addition, aimed to identify whether transfusion of washed red cells prevented hyperkalaemia and hypercalcaemia in the serum of neonates and infants undergoing open‐heart surgery. In an appendix at end of paper, a conference discussion was reported and the issue of the need to give all of this patient population irradiated red cells. The authors agree that not all of their patients may have needed irradiated red cells so the issue of high potassium and lactate levels may not be relevant to all
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Method of random sequence generation not reported
Allocation concealment (selection bias)	Unclear risk	No information was provided to enable an assessment of adequate allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not reported but theatre staff unlikely to be blinded as washing equipment would be visible to all
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported so insufficient information to make definite judgement
Incomplete outcome data (attrition bias) All outcomes	Low risk	All randomised patients were included in the analysis of outcome data and no patients were lost during follow‐up
Selective reporting (reporting bias)	Low risk	All outcomes mentioned in methods are reported in results
Other bias	Low risk	None reported