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Heparin versus saline flushes: Which is better? | VETgirl Veterinary CE Podcasts

In this VETgirl online veterinary CE podcast, we review the use of heparin versus saline flushes. Which is better?

Do you use heparinized saline flushes in your peripheral catheters? Do you ever wonder about their efficacy or potential complications? Well, while complications of using heparinized flushes are rarely reported in veterinary patients, we do worry about bleeding complications due to inadvertent heparinization (especially in small patients or neonates), drug interactions, and allergic reactions. In human patients, heparin-induced thrombocytopenia is also a concern. Numerous studies in human patients have shown no benefit over plain 0.9% NaCl flushes1, although a few have shown some protection against catheter clot formation, and based on these findings, many human hospitals have stopped using heparin in standard flushes.

Since no veterinary evidence exists to support or refute the use of heparinized flushes, Ueda et al out of Auburn University and University of Missouri performed a study called “Comparison of heparinized saline and 0.9% NaCl for maintaining peripheral intravenous catheter patency in dogs.” In this prospective, randomized clinical trial, they looked at 30 healthy junior surgery dogs. They placed 18-gauge cephalic catheters in all of the dogs, and then randomized them into three groups: 1 group (control, C) had no flushes performed until the end of the study period, 1 group (heparinized saline, HS) had their catheters flushed with 10 IU/ml heparinized saline every 6 hours for 42 hours, and the last group (saline, S) had their catheters flushed with 0.9% NaCl every 6 hours for 42 hours. When they compared these groups, they found that all of the dogs in the saline and heparinized saline groups had catheters that flushed easily at every time point. In the control group, the dogs were randomized to have their catheters flushed at different time points: 12 hours, 24 hours and 42 hours. Of these dogs, all had catheters that flushed easily except for 1 dog in the 42-hour group whose catheter was obstructed.

The authors also looked at ability to aspirate blood from the catheters, and found that while there was some difficulty in aspirating blood from some of the patients in the saline group, there was no statistical difference between groups. In the control group, all of the catheters were also easily aspirated except for the dog mentioned above in the 42-hour group with the obstructed catheter. Lastly, this study looked for evidence of phlebitis  and none was found in any of the saline or heparinized saline group dogs; one dog in the control group had mild erythema around the catheter and one had extravasation in the 42-hour control group.

So, what can we take away from this VETgirl podcast?

This study suggests that using 0.9% NaCl may be as effective as heparinized saline (10 IU/ml) to flush relatively large-bore catheters in dogs and maintain patency. While a significant difference wasn’t seen, the difficulty in aspirating from some of the saline-flushed catheters led the authors to suggest that heparinized flushes might be more appropriate if you’re planning on using a peripheral catheter for sampling.

Overall, this was small study looking at healthy dogs with relatively large peripheral catheters. In patients with smaller catheters, or those with systemic disease and a potential for hypercoagulability (e.g., cardiac disease, IMHA, pancreatitis, neoplasia, trauma, etc.), heparinized flushes might be indicated. One flaw of the study was that they only looked at one concentration of heparinized saline  – it would be interesting to look for differences between different concentrations, with the hope that we might be able to find the lowest effective heparin concentration to decrease potential complications. A prospective study looking at small patients (the ones that we often worry about systemically heparinizing with too much flushing) would be interesting and possibly more clinically relevant.

So, in conclusion, flushing peripheral IV catheters with 0.9% NaCl to maintain patency may be as effective as using heparinized saline in dogs with relatively large-bore (18 gauge) catheters. That said, if you’re placing a peripheral catheter with the intent of using it for serial blood sampling, heparinized saline flushes might be more appropriate.

References:

  1. Goode CJ et al. A meta-analysis of effects of heparin flush and saline flush: quality and cost implications. Nurs Res 1991;40(6):324-330.
  2. Ueda Y, Odunayo A, Mann FA. Comparison of heparinized saline and 0.9% NaCl for maintaining peripheral intravenous catheter patency in dogs. J Vet Emerg Crit Care 2013;23(5):517-522.

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