Abstract
Traditionally heparin has been the anticoagulant of choice for venous dialysis catheter locking. There is systemic leakage of heparin catheter locking solutions at the time of injection. Alternative agents, such as citrate, are increasingly being used. We are not aware of any data in the critical care literature on the effect of citrate locking of venous dialysis catheters on systemic ionised calcium (iCa2+). To assess the effect of 4% citrate locking of venous dialysis catheters on systemic iCa2+ in intensive care patients we performed a prospective observational study of 50 paired samples in 26 intensive care patients receiving 4% citrate dialysis catheter locking in an adult tertiary intensive care unit between May 2016 and December 2016. Arterial blood gas (ABG) analysis was performed prior to venous dialysis catheter locking and a baseline iCa2+ result obtained. The catheter was locked with 4% citrate solution. A further ABG was sampled between 30 and 120 seconds later and the iCa2+ results were compared. Patients were observed for clinical signs of hypocalcaemia. On average, there was little difference between the pre- and post-catheter locking iCa2+ (median pre-locking iCa2+ 1.19 mmol/l, mean change of +0.004 mmol/l, 95% confidence interval [CI] −0.004 to 0.013, P=0.34). There was no evidence this difference differed by length of catheter (P=0.26) or site of catheter (P=0.85) insertion, but there was some evidence that this differed by receipt of citrate dialysis circuit anticoagulation (P=0.013). Patients who received citrate dialysis circuit anticoagulation had an increase in catheter locking iCa2+ by 0.017 mmol/l (95% CI 0.005 to 0.028). Locking of venous dialysis catheters with 4% citrate solution has no clinically significant effect on systemic iCa2+ in intensive care patients with indwelling venous dialysis catheters.