Assessing the feasibility of infusing slow normal saline through a three-metre-longline to maintain patency of a peripheral venous cannula: A pilot study.

AIMS: In studies requiring repeated blood sampling, a cannula is typically inserted into a peripheral vein and used for regular blood draws. In some studies, subtherapeutic doses of heparin is infused overnight to maintain cannula patency; however, there is limited evidence supporting its use in this context. Normal saline infusions have been proposed as an alternative for extending cannula lifespan. This study aims to address the clinical need for data on blood collection techniques in healthy participants.

METHODS

The study was conducted at the Surrey Clinical Research Facility (CRF)/Surrey Sleep Research Centre (SSRC) sleep laboratory, involved five healthy males and females aged 18-35 years receiving a 6-h normal saline infusion. The primary outcome included the difficulty of drawing blood at hourly intervals, the incidence of phlebitis, re-cannulation and adverse events, as well as the condition of the cannulas post-infusion, assessed during each hourly blood draw.

RESULTS

By the fourth interval, 80% of blood draws were made with no difficulty, reducing to 40% by the end of the study. Self-limiting discomfort (score of 1 on VIP scale) was observed in two participant's cannulas; this resolved quickly in both cases. All five cannulas remained patent throughout and after the 6-h normal saline infusion.

CONCLUSIONS

While normal saline shows promise in maintaining peripheral cannula patency, a double-blinded clinical trial with a larger sample size is necessary to establish statistical significance in the comparison of heparin and normal saline.