Flushing of intravenous locks in neonates: no evidence that heparin improves patency compared with saline
- Correspondence to Sandra Bellini
School of Nursing, University Of Connecticut, 231 Glenbrook Rd., Storrs, CT 06269, USA;
Implications for practice and research
■ Nurses working in the neonatal intensive care unit (NICU) need to be mindful of the conflicting evidence supporting the use of heparin for maintenance of intravenous locks.
■ This study highlights the unsubstantiated and potentially dangerous routine practice of heparin administration for maintenance of intravenous locks in neonates.
■ Animal studies focusing on the use of heparin for maintenance of small-bore, low-flow central line catheters should be conducted to establish feasibility for subsequent neonatal studies.
The use of intravenous locks in neonates requiring stays in the NICU is widespread worldwide. These intravenous locks are used for administration of intermittent medications as well as administration of intravenous fluids and/or blood products. This study by Arnts et al investigates the efficacy of heparin for maintaining patency of intravenous locks as compared with normal saline solution in NICU patients. An additional aim was to examine potential other variables that may contribute to successful maintenance of intravenous locks. The study adds to a small body of research on the subject, which was of varying design and yielded conflicting results.1,–,3
This single-centre study from the Netherlands employed a double-blind, prospective randomised controlled design. Following consent from parents, subjects were randomised through appropriate procedures representing group assignment. Solutions for intravenous lock flushes were prepared on another unit to further ensure blinding. Subjects enrolled in the study included 88 neonates of >27 weeks gestation in total, 42 in the heparin group and 46 in the normal saline group.
Data collection, including gestational age, postnatal age, birth weight and current weight, was initiated upon the insertion of an intravenous lock. All nurses in the NICU were involved in the data collection, although five nurses received additional training and were responsible for determining whether intravenous locks were in need of removal, if in question. All intravenous locks were 24 gauge and were flushed a minimum of every 8 h with 0.7 ml (10 units heparin/ml) solution or with normal saline.
Data analysis examined instances and timing of intravenous lock failures between groups. Additionally, reasons for lock removal were examined and compared between groups.
Descriptive analysis demonstrated comparability between the study groups in terms of gender, birth weight, gestational age and current weight at the time of randomisation. The numbers of primary-line intravenous locks and numbers of infants with indwelling heparinised arterial catheters were also similar.
Comparison of intravenous lock mean patency times and intravenous lock failure rates was analysed using Kaplan–Meier analysis and Cox regression analysis. The results showed no statistical difference in intravenous lock patency times or failure rates between the saline group and the heparin group.
Overall, the present study is a strong one whose findings align with other recent publications.3 The authors clearly and explicitly state the research questions. A substantive review of pertinent literature is presented as background. The double-blind, prospective randomised controlled study design lends strength to the findings. Additional strengths of this study include standardisation of intravenous catheter types to 24-gauge only, standard volume and delivery times of instilled flush in both groups.
However, a few issues could be improved upon. First, the authors disclose the fact that the data presented in this study are more than 5 years old. Second, while great attention was given to standardising many important variables in this study, inter-rater reliability of the study nurses was not ensured, leaving room for potential bias when determining whether an intravenous lock needed to be removed. Finally, despite the assurance of a minimum number of intravenous lock flushes in a 24-h period, no attempt was made to standardise the maximum number of flushes between study groups. Given that that intravenous locks are used intermittently, the duration of patency could be impacted by increased frequency of flushes. Additionally, the small sample size of only 88 subjects limits the ability to generalise the study findings.
Despite these concerns, this study expands the body of existing literature on the routine use of heparin for intravenous lock patency in this population. This study should be replicated in a multi-centre trial to increase generalisability. The routine use of heparin in neonates is a potentially dangerous and as yet unsubstantiated practice1,–,4 and requires further study.