Vitamin D serum levels in multiorgan failure critically ill patients undergoing continuous renal replacement therapies

Introduction
Severe vitamin D deficiency in critically ill patients is linked to mortality. There are no scientific data regarding vitamin D status in critically ill patients undergoing continuous renal replacement therapies.

Material and methods
We aimed to measure vitamin D serum levels in critically ill patients with multi­organ failure undergoing continuous renal replacement therapies. Vitamin D serum measurements in 12-hour time intervals were performed in 20 patients undergoing continuous renal replacement therapies through continuous veno-venous haemodiafiltration (the study group). The results were then compared with the historical control group (20 patients without renal replacement therapy).

Results
In the control group the median vitamin D level initially decreased, then stabilised around the fourth and fifth measurement, after which it appeared to increase unevenly. In the study group the median vitamin D level decreased considerably, and then stabilised around the third measurement. Although the differences between groups gradually increased for the last three measurements, there was insufficient evidence to indicate that they were statistically significant (P > 0.05). Significant correlations were found between the time of measurement and the level of vitamin D in the study (R = –0.31, P = 0.0002) and control groups (R = –0.18, P = 0.0341).

Conclusions
Vitamin D serum levels decline rapidly during the course of critical illness in patients undergoing continuous renal replacement therapies. No statistically significant differences in the levels of vitamin D between the study and control groups were found.