Venipuncture vs. IVC: Samples Similar No Matter How You Stick It

We've seen them before--hospitalized equine patients made anxious, even fractious, by the drawing of multiple blood samples via direct venipuncture.

But here's good news for veterinarians and nursing staff who dislike using the method on resistant patients. According to a recent study from researchers at the University of Pennsylvania's New Bolton Center, blood drawn with an indwelling intravenous catheter (IVC) yielded no statistically significant or clinically relevant differences compared to samples taken by direct venipuncture.

An IVC allows for less stressful sampling, but because the route is generally used to administer medications and fluid therapy, many clinicians fear that blood taken via IVC would be diluted or altered, noted the researchers. The study, E-published Aug. 24 by the Journal of Veterinary Internal Medicine, found that blood samples obtained by IVC have clinically equivalent values to those taken by direct venipuncture in commonly performed analyses.

"This study gave us some valuable information for something we do every day," said Maeva Louis May, DVM, Dipl. ACVIM, a lecturer in internal and sports medicine at New Bolton and lead author on the study. "Hospitalization is a stressful time for the animal, and there are times we actually end up getting blood up to four times per day. It's trying for the animal and the nurses, and we often see horses become more difficult to handle. One thing we don't want to compromise is the human-animal bond."

May and her colleagues studied 50 horses admitted to New Bolton for a variety of medical and surgical conditions between August 2008 and June 2009. Of the horses, 25 received constant rate crystalloid therapy, and 25 received low-volume IV medication. Fluids were stopped five minutes before sampling and in the case of IVC collections, a standardized pre-sample (300% of catheter dead space) was first taken and discarded to protect against dilution or alteration.

"We wanted to be able to say, 'Even on animals that receive IV fluids, as long as you stop the fluids and take a good pre-sample, those results (taken via IVC) are comparable,'" May said.

Veterinary professionals interested in implementing the IVC method should note that additional investigation is required to establish whether increased complications such as phlebitis (vein inflammation) or bacteremia (bacteria in the blood) are associated with this technique. Also, further studies are needed to assess whether increased complications arise when blood is drawn repeatedly from catheters.

The abstract of the study, "Comparison of Hematologic and Biochemical Results on Blood Obtained by Jugular Venipuncture as Compared with Intravenous Catheter in Adult Horses," is available on PubMed.

About the Author

Claire Novak

Winner of the 2011 Eclipse Award for Feature/Commentary and the 2008 Louisville Metro Journalism Award for Sports Writing, Claire Novak has melded her love for human-interest journalism and the equine breed into a successful Turf writing career. Since her first freelance article on racing was published at in 2005, her byline has appeared in the New York Times, ESPN The Magazine, and on, among others. She lives near Lexington and, when not writing about racing, can often be found jumping her Thoroughbred, Bob.

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