Changes in erythrocyte calcium and potassium in patients during HD and CAPD

The purpose of this study was to determine the changes in calcium and potassium content in the red blood cells (RBC) of uremic patients during a hemodialysis (HD) session and a 6/hrs CAPD exchange. RBC calcium and potassium were determined in 20 patients on HD in three blood samples collected at 0'-HD (pre-HD), 45'-HD and 240'-HD (end-HD), in 20 patients on CAPD, in two blood samples, collected at 0' time (pre-inflow) and 120', (solution in peritoneal cavity) during a 6/hrs exchange (4 exchanges / 24 h) and in 20 normal subjects. The mean value (+/-SD) of RBC calcium in controls was 15.6+/-3.75 micromol/L, in hemodialysed patients at 0'-HD, 45'-HD and 240'-HD 51.5+/-8.5, 70.4+/-12.5 and 51.1+/-10 micromol/L respectively and CAPD patients at time 0' and 120 of an exchange 53.6+/-23.4 and 70.6+/-9.2 respectively. These values show that RBC calcium in hemodialysed patients is generally significantly higher (p < 0.0001) than in controls. The value at 45'-HD is also significantly higher (p < 0.0001) than at 0' or 240'-HD. In CAPD patients, at 0' and 120' of a 6/hrs exchange, it is significantly higher (p < 0.0001) than in controls, as is the value at 120' (p < 0.001) in comparison to 0'. The mean value (+/-SD) of RBC potassium at the aforementioned time measurements were 95.9+/-3.34, 92.5+/-4.32 and 93.85+/-3.89 mmol/L respectively for patients on HD, 95+/-3.3 and 94.6+/-5.28 mmol/L respectively for patients on CAPD and 99.1+/-3.70 mmol/L in controls. These values show that RBC potassium of hemodialysed patients is significantly lower in comparison to that of controls (0'-HD: p < 0.01, 45'-HD and 240'-HD: p < 0.001); also the value at 45'-HD and 240'-HD is significantly lower (p < 0.001, p < 0.01 respectively) when compared to that at 0'-HD. In patients on CAPD, at 0' time and 120' during 6/hrs exchange, potassium is significant lower (p < 0.001) in comparison to that of controls. In conclusion, uremic patients present high erythrocyte calcium and low potassium with fluctuation during HD-sessions and CAPD 6/hrs exchange.