Maintaining normal levels of ionized calcium during citrate-based renal replacement therapy is associated with stable parathyroid hormone levels

Raimundo, M., Crichton, S., Lei, K., Sanderson, B., Smith, J., Brooks, J., Ng, J., Lemmich Smith, J., McKenzie, C., Beale, R., Dickie, H. and Ostermann, M. (2013) Maintaining normal levels of ionized calcium during citrate-based renal replacement therapy is associated with stable parathyroid hormone levels. Nephron - Clinical Practice, 124 (1-2), 124-131. (doi:10.1159/000355860).

Abstract

Background/Aims: Citrate is an effective anticoagulant during continuous renal replacement therapy (CRRT). Previous studies showed raised parathyroid hormone (PTH) levels when aiming for serum ionized calcium [Cai] between 0.8 and 1.1 mmol/l. Our objective was to assess whether citrate-based CRRT with physiologic target systemic [Cai] between 1.12 and 1.20 mmol/l could maintain stable PTH levels.
Methods: Measurement of intact PTH (PTHi) in 30 consecutive critically ill patients treated with citrate-based CRRT.
Results: Thirty patients [mean age: 70.4 (SD 11.3) years; 56.7% males] were enrolled. Mean serum [Cai] was 1.16 mmol/l (SD 0.09), 1.13 mmol/l (SD 0.09), 1.17 mmol/l (SD 0.05) and 1.16 mmol/l (SD 0.04) at baseline, 12, 24 and 48 h, respectively (p = 0.29). Median PTHi levels (interquartile range) at baseline, 12, 24 and 48 h were 66.5 (43-111), 109 (59.5-151.5), 88.5 (47-133) and 85 pg/ml (53-140), respectively. The differences between baseline and 12 h and across all time points were statistically not significant (p = 0.16 and p = 0.49, respectively). In a mixed-effects model, each 0.1 mmol/l increase in serum [Cai] was associated with a 31.2% decrease in PTHi (p < 0.001). Results were unchanged after adjustment for age, gender, magnesium, phosphate, arterial pH and time spent on CRRT.
Conclusions: Maintaining systemic [Cai] within the physiologic range was associated with stable PTHi levels.

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Contributors

Author: C. McKenzie

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