Objective: High concentrations of potassium and lactate in irradiated red cells transfused during cardiopulmonary bypass may have detrimental effects on infants and neonates undergoing cardiac surgery. The effects of receiving washed and unwashed irradiated red cells from the cardiopulmonary circuit on serum potassium and lactate concentrations were compared. Methods: The study population included neonates and infants undergoing heart surgery for complex congenital heart disease. A control group (n = 11) received unwashed irradiated red cells and the study group (n = 11) received irradiated red cells washed in a cell saver (Dideco Electa) using 900 ml of 0.9% saline prior to pump priming. Potassium and lactate concentrations were compared before, during and after bypass. Results: Washing irradiated red cells reduced donor blood [potassium] from > 20 to 0.8 AE 0.1 mmol/l, and [lactate] from 13.7 AE 0.5 to 5.0 AE 0.3 mmol/l ( p < 0.001). The resulting prime had significantly lower [potassium] and [lactate] than the unwashed group (potassium 2.6 AE 0.1 vs 8.1 AE 0.4 mmol/l, p < 0.001; lactate 2.6 AE 0.2 vs 4.6 AE 0.3 mmol/l, p < 0.001). Peak [potassium] in the unwashed group occurred 3 minutes after going on bypass (4.9 AE 0.3 mmol/l) and during rewarming (4.9 AE 0.4 mmol/l). These were significantly higher than the washed group (3.1 AE 0.1, p < 0.001 and 3.0 AE 0.1 mmol/l, p < 0.001). The [potassium] was greater than 6.0 mmol/l for 4 out of these 11 unwashed patients compared with none of the washed group. Immediately postbypass the washed group had significantly lower serum [potassium] (3.2 AE 0.1 vs 4.2 AE 0.2 mmol/l, p = 0.002). There was no significant difference in [lactate] between groups during and after cardiopulmonary bypass. Conclusions: The washing of irradiated red cells reduces potassium and lactate loads and prevents hyperkalaemia during cardiopulmonary bypass. The washing of irradiated red cells should be considered in neonates and infants undergoing cardiac surgery for complex congenital heart disease. #

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