Flushing Frequencies
Does More Frequent Flushing Improve Peripheral IV Outcomes?
Flushing peripheral intravenous catheters is such a routine part of clinical practice that we rarely stop to consider what is actually happening inside the vessel when we flush.
Keogh and colleagues examined whether the frequency of saline flushing affected peripheral intravenous catheter (PIVC) failure, coagulation, vascular changes, and thrombus formation.
The researchers used a randomized, counterbalanced human model involving 17 healthy adult participants and 34 PIVCs. Each participant had bilateral cephalic-vein cannulation. One catheter received low-frequency flushing at insertion and again at removal five hours later, while the other received more frequent flushing throughout the five-hour study period. The investigators also used ultrasound in a subset of seven participants to examine vessel diameter, catheter-to-vein ratio, blood-flow velocity, and thrombus formation.
What did they find?
Frequent flushing did not reduce catheter failure.
Only one of the 34 catheters failed during the five-hour study period. That catheter was in the low-frequency group, but there was no statistically significant difference in failure between groups.
However, more frequent flushing was associated with an increase in prothrombin time (PT) after five hours. The authors suggest this may indicate consumption or inhibition of factors involved in the extrinsic coagulation pathway, although the clinical significance remains uncertain.
Perhaps the most striking finding came from the ultrasound substudy.
At five hours, suspected subclinical intraluminal thrombosis was identified adjacent to or immediately proximal to the catheter in:
6 of 7 frequently flushed vessels (87.5%)
and
5 of 7 less-frequently flushed vessels (71.4%).
The difference between flushing groups was not statistically significant, but the overall prevalence of thrombus formation was notable. Importantly, these thrombi were subclinical and did not interfere with catheter function during the study.
Why does this matter?
A functioning peripheral IV is not necessarily a physiologically quiet peripheral IV.
Cannulation places a foreign device inside a blood vessel, where the catheter, vessel wall, blood flow, insertion injury, and subsequent infusions all interact. The investigators observed dynamic changes in vessel caliber, blood-flow velocity, coagulation measures, and thrombus formation after cannulation.
The study also challenges the assumption that more frequent flushing automatically means better catheter maintenance. Within this five-hour experimental model, increasing flushing frequency did not improve catheter survival or prevent subclinical thrombosis.
Important limitations
This was a small preclinical study involving healthy volunteers, not hospitalized patients receiving typical IV therapy. Catheters were observed for only five hours, and the ultrasound substudy included just seven participants. The authors specifically describe the sonographic portion as a feasibility study and emphasize the need for larger clinical trials.
The findings therefore should not be interpreted as evidence to change clinical flushing protocols. Instead, they provide an interesting look at the physiology occurring around an indwelling PIVC and raise important questions for future research.
CCE Takeaway
Peripheral IV care doesn't end when the catheter is successfully placed. What happens between the catheter, blood, vessel wall, and every subsequent intervention may influence the life of that IV.
Successful vascular access means thinking beyond insertion—and continuing to ask how our everyday practices affect the vessel after the catheter is in place.
Reference
Keogh S, Hawthorn AM, Shibeeb S, et al. Impact of Different Flushing Frequencies on Peripheral Intravenous Catheter Failure, Coagulation, and Tissue Injury—A Counterbalanced Preclinical Human Trial. Journal of the Association for Vascular Access. 2022;27(2):19–29. doi:10.2309/JAVA-D-22-00006.
