Surgery

A practical guide to postsurgical ventral midline SSIs

By Paul Basilio

Surgical site infections (SSIs) are a common complication following colic surgery in horses. The prevalence of these infections ranges from 10% to 37% in the literature, but since clinical signs often don’t appear until after the horse is discharged, the prevalence is likely higher, according to Jesse Tyma, DVM, DACVS-LA, a veterinarian at Rhinebeck Equine in New York.

“For a repeat celiotomy—or recut—in the early postoperative period, that risk more than doubles,” said Dr. Tyma during a presentation at the 71st Annual AAEP Convention in Denver.

SSIs can result in longer hospitalizations, increased costs, delayed return to work, and up to a 12-fold increase in the risk for incisional hernias. In horses undergoing colic surgery, the development of an incisional hernia is statistically associated with decreased odds of returning to their original use.

“Early recognition and appropriate management of these SSIs is so important,” Dr. Tyma said.

Clinical signs that can point the practitioner to an SSI include discharge, fever, pain on palpation and localized swelling. Dr. Tyma explained that it’s also important to note that localized swelling in the absence of other clinical signs can be normal, and may be more prominent in horses with unbandaged vs bandaged abdomens.

“Personally, I prefer sending most postoperative colic horses home unbandaged,” she said, adding that an unbandaged abdomen allows for more careful incisional monitoring rather than a perceived improvement in incisional protection that can come with a bandaged abdomen.

If a veterinarian believes the patient likely has an SSI, Dr. Tyma strongly recommended establishing a line of communication with the operating surgeon to collaborate on appropriate management and biosurveillance practices.

“Open communication across primary, emergency and referral care teams is paramount for optimizing care, delineating clear expectations and improving patient outcomes,” she said.

Management of the SSI involves converting a primarily closed incision to a surgical wound that is allowed to heal by second intention. The goal is to establish drainage, manage the infection and support the abdominal wall.

“The infected incision should be approached with a plan and appropriate physical and chemical restraint,” Dr. Tyma said. “Ideally, you would have an experienced handler, a twitch or a lip chain, and generous IV sedation.”

“For incisions that are already draining, I aseptically prepare the incision, insert hemostats at the drainage site, and bluntly separate the skin at this level,” she explained, “I’ll follow that with sampling of the subcutaneous space with a swab. If the skin is healed over, I recommend using a #15 blade to make a stab incision adjacent to the site of drainage or over a sonographic fluid pocket.”

Then she uses hemostats or her index finger to explore the wound cranially and caudally, and bluntly dissect the skin until no skin shelf remains, ensuring adequate dependent drainage of any trapped or necrotic debris. If the skin has healed over, she’ll remove any skin sutures, staples or subcutaneous sutures in the infected area and lavage the wound. Results of culture and susceptibility testing can guide antimicrobial therapy, if needed.

“In some cases, the linea alba and linea suture may well be exposed,” Dr. Tyma warned. “Ensure that the linea alba is intact with no gapping. If there is gapping, then this is an emergency. Place a belly bandage and contact the surgeon, because that horse is at risk for evisceration.”

With adequate drainage, most cases will not require antimicrobials. When they are used, Dr. Tyma said she prefers to base her antimicrobial choice on culture results. “There’s also mixed empirical data regarding the utility of topical antibiotics for midline SSIs,” she said, adding “she routinely give these horses NSAIDs for several days after the procedure.”

Postprocedural care involves daily cleansing and dressing changes at the start. When the wound becomes less productive, cleansing and dressing changes can be done every other day. Granulation tissue typically develops within a week and can take up to a month to cover the linea alba. After granulation, the horse’s risk for herniation decreases.

“Stall confinement is essential to minimize herniation risk,” Dr. Tyma said. “After establishing drainage and once granulation has begun, the horse can be hand-walked, but it’s imperative to avoid unrestricted exercise until at least 1 month after complete granulation.” MeV