Introduction: Elevated serum parathormone (PTH) levels have been observed in acute kidney injury and are related to calcium-phosphate metabolism disturbance, decreased renal production of 1,25 dihydroxyvitamin D3, impaired renal PTH excretion, and other renal-independent factors. There are no data regarding PTH concentration kinetics in critically ill patients undergoing continuous renal replacement therapies (CRRT) in an intensive care setting. The primary objective of this study was to investigate trends in PTH serum levels in critically ill patients with multiorgan failure undergoing CRRT, by performing periodic PTH measurements in the acute phase of critical illness.

Material and methods: This was a single-centre, prospective, observational study conducted in an mixed, university-affiliated intensive care unit. Critically ill patients who fulfilled all of the following criteria were included: respiratory failure; circulatory failure; acute kidney injury treated by CRRT; and sequential organ failure assessment score (SOFA score) of 5 or more. Patients who met any of the following criteria were excluded: acute liver failure; hypercalcemia at admission (total calcium serum level > 10.6 mg/dL; total ionized calcium plasma level > 1.35 mmol/L); parathyroid gland disease; end-stage renal disease; patients undergoing therapeutic plasma exchange or extracorporeal membrane oxygenation procedures; aged under 18 years;  pregnant; and life expectancy after admission to the intensive care unit anticipated to be less than 72 hours as assessed by the investigator.

Results: Thirty patients met the inclusion criteria. A statistically significant change in PTH over time was observed (Friedman ANOVA; p = 0.0001). The post-hoc test showed a statistically significant decrease in PTH: measurements 5–8 relative to measurement 1, and measurements 4–8 relative to measurement 2 (p < 0.05). No significant correlations between 25 hydroxyvitamin D3 deficiency, age, diagnosis, SOFA score, and PTH levels were observed. A statistical test indicated that serum concentrations of PTH were significantly higher in the de novo sepsis group (p < 0.05).

Conclusions: The PTH serum concentration decreases during the course of CRRT in the majority of patients. When the course of the disease starts to be complicated by sepsis, PTH serum levels then remain high. A probable reason for this is the existence of the inflammatory state triggered by sepsis.