Tap water is fine for cleaning most horse wounds, researchers conclude

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Tap water should be used instead of sterile saline for washing most horse wounds, a panel of experts has concluded after examining the available evidence.

No study was found investigating the issue in horses that met the inclusion criteria for their review. However, there were human studies on the subject, including two reviews.

The first concluded there was no difference in infection and healing rates of acute or chronic wounds cleansed with either tap water or normal saline.

The second similarly found no evidence that using tap water to cleanse acute or chronic wounds in adults increased infection or healing rates, and there was some evidence that it reduced infection when compared to saline.

The overall conclusion was that there is no evidence on the effectiveness of tap water versus saline for lavage in equine wounds, the researchers reported in the Equine Veterinary Journal.

“Tap water should be considered for the lavage of equine wounds rather than sterile saline, based on strong evidence in the human literature,” they said.

It should be of drinkable quality. If unavailable, boiled and cooled water or distilled water should be used.

For the paper, Professor of Veterinary Surgery Sarah Freeman, with the School of Veterinary Medicine and Science at the University of Nottingham in England, and her colleagues set out to develop evidence-based guidelines on equine wound management.

They examined available evidence, focused on a core set of questions around wound management as proposed by a panel of veterinarians. Their work extended to human evidence, particularly where information was lacking in horse-related studies.

In all, 306 veterinary studies and 25 human evidence papers were whittled down to a series of key recommendations for horse wound treatment. The latter were all systematic reviews, which summarised evidence from hundreds of studies on wounds in people.

There is some evidence that silver sulfadiazine is beneficial in infected wounds, but it is also toxic to early epithelial cells so may slow wound healing.
There is some evidence that silver sulfadiazine is beneficial in infected wounds, but it is also toxic to early epithelial cells so may slow wound healing.

Key among the horse-wound findings is the use of tap water over saline. However, povidone-iodine should be considered for washing contaminated wounds. (Povidone-iodine, also known as iodopovidone, is an antiseptic used for skin disinfection before and after surgery.)

Topical use of silver sulfadiazine may not be suitable for acute wounds, they say.

Freeman told Horsetalk that the use of silver is interesting. “There is some evidence that it is beneficial in infected wounds, but it is also toxic to early epithelial cells so may slow wound healing.”

It would be best, she said, if people avoided using it indiscriminately on all wounds. “Used appropriately it has benefits, but it should not be used on everything.”

Optimal pressure for washing wounds is around 13 pounds per square inch, the study team found (what they described as medium pressure).

Turning to wound debridement and closure, the researchers said debridement pads should be considered for wound preparation; and that larvae debridement should be considered in selected cases. Hydrosurgery — use of a specialist high-pressure water jet which acts as a scalpel — should also be considered in acute contaminated wounds.

There was not enough evidence to make recommendations on the use of chemical debridement.

Honey has some benefits

On therapeutics, the authors say there is currently insufficient evidence on therapeutic ultrasound and laser therapy. Evidence on honey shows some benefits for some types of wounds or phases of healing, but there is limited or no evidence of an increase in overall healing or cosmetic outcome.

Discussing their findings, the authors said many of their recommendations were based on human literature because of the limited horse evidence available in some areas.

“This study has highlighted that there is currently a lack of evidence to draw conclusions on the use of a range of treatments, including the use of silver dressings, chemical debridement, laser therapy and ultrasound therapy.”

The authors say that their work represents a review of current equine and human evidence, but a full appraisal would require systematic and umbrella reviews on each topic. They say there is a need for high-quality evidence in the veterinary literature across all areas of wound management.

Freeman told Horsetalk that her team is currently working with The British Horse Society on owner knowledge gaps and new data on how different wounds heal. Over the next year, some new resources will be developed for horse owners, likely resulting in a wound campaign.

She says the British Equine Veterinary Association has already been releasing top tips around the wound guidelines, including the tap water.

“It’s something recommended by the World Health Organisation for cleaning wounds, but vets and animal owners are not always aware. It’s very basic, but letting people know that, as long as it is clean, drinkable water, then turning on the hosepipe and flushing the wound as soon as you see it, will really help in removing some of the bacteria and dirt as early as possible and reduce the risk of infection.”

The review team comprised Freeman; Neal Ashton with Oakham Veterinary Hospital, England; Yvonne Elce and Anna Hammond, with the Equine Referral Hospital at Langford Vets, Bristol, England; Anna Hollis, with the Centre for Equine Studies at the now-closed Animal Health Trust in Newmarket, England; and Greg Quinn, with the Waikato Equine Veterinary Centre in Cambridge, New Zealand.

BEVA primary care clinical guidelines: Wound management in the horse
Sarah L. Freeman, Neal M. Ashton, Yvonne A. Elce, Anna Hammond, Anna R. Hollis and Greg Quinn.
Equine Veterinary Journal, 28 May 2020, https://doi.org/10.1111/evj.13289

The abstract can be read here.

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