Plasma Parathormone Levels during Citrate Anticoagulated Continuous Venovenous Hemofiltration in ICU Patients

Continuous venovenous hemofiltation (CVVH) with citrate anticoagulation has been shown to be associated with substantial losses of calcium and negative calcium balance in ICU patients, which may lead to excessive bone loss and osteoporosis. The aim of this study is to investigate whether plasma parathormone monitoring can identify patients with negative calcium balance during CVVH. This is a retrospective single-center study of all adult ICU patients treated with citrate CVVH from 2021 to 2023. PTH was measured routinely once per week. Calcium excretion in ultrafiltrate fluid and CVVH calcium balance were measured daily. In total, 274 PTH measurements were performed in 111 patients. In 61 measurements (22%), PTH was higher than the upper limit of normal (>8 pmol/L). If PTH was higher than normal, plasma ionized calcium was less than 1.16 mmol/L in 77% of cases and hypercalcemia was never present. In a subgroup of patients treated with CVVH for at least 36 h in the preceding 72 h, PTH values were similar for quartiles by cumulative calcium balance. Increased plasma concentrations of PTH are frequently found in ICU patients treated with citrate CVVH, but no association was found between PTH and the CVVH calcium balance over the last 72 h.