Washing of irradiated red blood cells in paediatric cardiopulmonary bypass: is it clinically useful? A retrospective audit.

Objective: Despite the introduction of smaller cardiopulmonary bypass (CPB) circuits for paediatrics, it is frequently necessary to add irradiated red blood cell concentrate (IRBC) to maintain adequate haemoglobin levels and the oxygen carrying capacity. Irradiation of blood weakens the cell membranes and results in an increase of lactate and potassium concentration. In addition, prolonged shelf time of IRBC may enhance its lactate level. To avoid the adverse effects of increased lactate and potassium concentration during paediatric bypass, prewashing of homologous blood in a cell-saving device was implemented at our institution. A retrospective audit of clinical data was performed to assess the relevance of this method.

Methods: Preceding the introduction of the blood pre-washing, we investigated 14 units of IRBC for lactate, potassium levels and shelf time. Afterwards, we evaluated the CPB and laboratory data from 69 patients with body weight <10 kg and the lactate levels in the priming of the bypass circuit.

Results: The shelf time of blood units was 7.6 ± 2.7 days (minimum 5, maximum 14 days) with lactate concentration of 12.6 ± 2 mmol/land potassium concentration of 16.2 ± 4.7 mmol/l. In the priming after pre-washing, the lactate concentration was significantly lower than the standard priming (2.5 ± 0.9 vs 4.5 ± 20 mmol/l, p = 0.002). At the start of bypass, the lactate concentration after pre-washing was still lower (1.5 ± 0.4 vs 1.9 ± 0.9 mmol/l; p = 0.04), but at the end of bypass we detected a significant increase of lactate in the pre-washed group (1.5 ± 0.4 vs 2.2 ± 1.1 mmol/l, p = 0.01). There was no significant difference between the groups at the end of bypass (1.8 ± 0.9 vs 2.2. ± 1.1 mmol/l, p = 0.17). Other clinical and patient data were not significantly different.

Conclusions: Our retrospective audit shows that pre-washing of IRBCs is not associated with decreased lactate levels at the end of CPB compared with standard use of IRBCs, suggesting that the added value of pre-washing of IRBCs on minimisation of lactate levels during CPB remains doubtful.