Preventing Catheter Site Complications
In equine hospitals, intravenous (IV) catheters are often placed in the large jugular vein in the neck of horses to make it easier for everyone (the horse included) to give the animal fluids and/or medication. However. any time the body's normal barriers (e.g. the skin) are broken (e.g. by placing a catheter through the skin into a vein), there is an increased risk of infection. Catheter site complications can range from mild inflammation of the skin around the catheter, to serious infection causing thrombosis (blockage) of the vein and abscesses.
Several routine practices are used to help reduce to risk of complications from catheters. Typically, a small (~2 cm X 2 cm) area of skin over the vein is shaved or clipped. Next, the area is usually cleaned with antibacterial soap, and then wiped several times with alcohol and a disinfectant like chlorhexidine or povidone iodine. This is done to help reduce the number of bacteria on the skin at the site where the catheter is placed so the site is less likely to become infected.
At some facilities, clipping the neck before the catheter is places is often not performed. Also, sometimes owners request that the site not be clipped because they don't want it to be apparent that their horse needed a catheter because it was sick or had surgery. I've always been very reluctant not to clip, although there hasn't been a lot of objective evidence proving that clipping is important.
A recent study published in the Veterinary Record (Geraghty et al. 2009) has provided some information about the effects of catheter site preparation. In this study, researchers looked at different skin preparation methods. They cultured swabs from the skin before and after different procedures.
The most important findings were:
- Clipping and shaving had a significant effect on bacterial numbers, even before disinfection. Disinfection resulted in essentially eliminating all detectable bacteria, whether the haircoat was clipped, shaved or left intact.
- Clipping, shaving or leaving the haircoat intact were equally effective if a disinfectant was used afterwards. However, clipping or shaving were still preferred over leaving the haircoat intact. (Clipping or shaving both reduced initial bacterial numbers, and this might be important in situations where the haircoat is highly contaminated or dirty).
- Clipping and shaving may be useful for reasons other than disinfecting the catheter site. They can make the vein easier to see, which may make it easier to place the catheter. Difficulty placing the catheter and repeated attempts to place the catheter can cause additional tissue damage and most likely increase the risk of complications. Leaving the haircoat intact also may increase the risk of introducing foreign material (e.g. hair, dirt) into the body when the catheter is placed.
- Since it was possible to effectively eliminate detectable numbers of bacteria from an unclipped haircoat with proper disinfection, placing a catheter without clipping is acceptable "when rapid intravenous catheterisation is necessary as a clinical priority." To me, this means that it's okay to place a catheter without clipping if the time needed for clipping might make a major difference to the chances of the patient surviving. This is not the case in situations where people just want to avoid evidence that their horse has had a catheter. While the true risk of not clipping is unknown, it makes no sense to not clip when there is no real downside (other than aesthetics) and there is a logical possibility that it could decrease the risk of complications.
- Chlorhexidine and povidone iodine were equally effective disinfectants. However, chlorhexidine has been shown to be more effective in people at preventing infections. It has a broader spectrum of activity against microorganisms, and is less inhibited by dirt and debris. The small size of the study might have limited the ability to detect a difference between the two products. Since there is no real reason to use povidone iodine over chlorhexidine, and chlorhexiinde has been shown to be better in people, it makes sense to use it in horses.
This study provides some very useful information. Because it looked at bacterial numbers on the skin, not complications/infections per se, we have to be careful not to over-interpret the results. This study (as usual for studies like this) only assessed the transient bacterial population on the skin, not the resident population. The resident population is deeper in the skin and harder to kill. So, even though no bacteria were found after certain procedures, we can't assume the area was truly sterile. Nonetheless, the transient bacteria tend to cause most of the problems, so this type of study is still useful.
Intravenous catheterization is a very important tool in equine medicine. While there are always risks, the benefits of having a catheter in place almost always greatly outweigh any risks. Careful preparation of the catheter site, good catheter placement technique and close monitoring of the catheter site help reduce the risk of complications.
