Background On our paediatric intensive care unit (PICU), we have historically used heparin in 0.9% sodium chloride as a continuous flush to maintain patency of arterial and central venous pressure (CVP) central lines. Practice varies across the UK, some units use heparin in sodium chloride whilst others use sodium chloride alone to maintain line patency. Currently in paediatrics there is not enough evidence to change local practice by removing heparin from the flushes.¹ A cost saving scheme was identified whereby using heparin in sodium chloride 0.45% was cheaper than using heparin in sodium chloride 0.9% (both products from Baxter). A proposal was put together and approved by the PICU quality improvement group, demonstrating that in theory, there should be no significant loss of sodium to patients due to the change in fluids. Although it may seem that flushes would not contribute a large proportion of a patient’s fluid requirement, in a typical 2.5 kg patient post cardiac surgery, 2 ml/hour would actually provide 40% of the patient’s total fluid allowance. This change in practice was implemented in June 2018.

Aim The aim of this audit was to establish whether patients receiving heparin in sodium chloride 0.45% had lower sodium blood levels or a greater drop in sodium levels than patients on heparin in sodium chloride 0.9%. We also evaluated whether a higher incidence of line blockage was reported in either group.

Methods Data was collected retrospectively using the Phillips ICCA electronic prescribing system, using 25 patients pre (April 2018) and 25 patients post (June and July 2018) implementation of the heparin in sodium chloride 0.45% flushes. Sodium blood gas levels were used as these were more consistently taken than plasma blood samples.

Results The data showed that heparin in sodium chloride 0.45% did not reduce sodium levels in patients. In each group 1 patient required additional sodium supplementation and 2 patients’ lines became blocked and therefore were removed. The average sodium on admission in the heparin in sodium chloride 0.9% group was 139.96 mmol/L (CI 95% ±1.17 mmol/L) compared to the heparin in sodium chloride 0.45% group which was 135.68 mmol/L (CI 95% ± 1.91mmol/L). The average sodium level on either line removal or discharge from PICU was 138 mmol/L (CI 95% ± 1.35mmol/L) in the heparin sodium chloride 0.9% group compared to 135.72 mmol/L (CI 95% ± 1.88 mmol/L) in the heparin sodium chloride 0.45% group. The results indicated that patients within the pre-change group lost, on average, 2 mmol/L sodium compared to their admission sodium levels compared to 0.04 mmol/L in the post-change group. The reason for this difference is unclear would warrant further investigation into alternative sources of sodium e.g. drug infusions and additional fluids which were outside of the scope of this audit.

Conclusion The change from using heparin in sodium chloride 0.9% to heparin in sodium chloride 0.45% was not found to lead to a reduction in plasma sodium levels in our patient population. Limitations to the audit include not considering alternative sources of sodium and a small patient population.

Reference

1. Beswick T, Skipp M. Should heparin based flushing solutions be used in preference to saline to maintain the patency of indwelling intravascular catheters and cannulae? – SPS - Specialist Pharmacy Service [Internet]. Available at www.sps.nhs.uk. 2016 [accessed 3 Aug 2018]. Available from: https://www.sps.nhs.uk/articles/should-heparin-based-flushing-solutions-be-used-in-preference-to- saline-to-maintain-the-patency-of-indwelling-intravascular-catheters-and-cannulae/