Potassium levels in exchange transfusion.

In the Royal Maternity Hospital, Belfast, in common with other centres treating haemolytic disease of the newborn, the number of infants requiring exchange transfusion has been increasing steadily in the past few years. In 1950 there were seven live-born affected infants, of whom five were treated, all successfully, by exchange transfusion, in 1954 there were 42 live-born affected infants of whom 34 were treated by exchange transfusion, 31 surviving. At the end of 1952 and the beginning of 1953 there were two deaths during the actual transfusion in infants who were comparatively mildly affected. The deaths were sudden and unexpected, and it occurred to us that they might have resulted from an excess of potassium in the bottles of blood used for the exchange. The plasma from several random bottles was therefore analysed, and it was found that levels of40 mg. % were not uncommon, even though none of the blood had been more than one week in store. In an attempt to determine whether hyperpotassaemia might in fact be the cause of death in these infants, an investigation was planned on the following lines:In every case where it was decided to treat the baby by exchange transfusion, samples of blood were taken from the umbilical vein at the beginning of the tranfusion and after every 100 ml. of the exchange. These samples were taken into heparinized tubes and the plasma separated within four hours. Similar samples were taken from the bottles of stored blood used for the exchange. In general, the criteria for transfusion were those suggested by Mollison (1952), and an exchange of 60 ml. of packed cells per lb. weight was aimed at. When data had been obtained from 20 infants (21 transfusions) they were examined; the potassium levels for this control group are shown in Fig. 1. It will be seen that 13 of the 104 samples had potassium levels of 28 mg. % or above, and that