Equine surgery is not without potential complications of infection. At the Koret School of Veterinary Medicine in Israel, a study examined post-operative complications related to 198 surgical procedures on 167 horses between November 2011 and February 2013 [Kelmer, G.; Paz, I.; Tatz, J.A.; et al. "Factors Associated with Surgical Site Infections in Horses: A Retrospective Study." Israel Journal of Veterinary Medicine June 2020, vol. 75, no. 2].
The research report noted that post-operative surgical site infections created difficulties with recovery, increased duration of hospitalization, interfered with return to function, increased client costs, as well as caused an increase in morbidity and mortality of the horses.
This study evaluated 40% abdominal surgeries, 30% orthopedic surgeries and 30% other procedures with a general surgical site infection (SSI) of 9-20%.
Infection incidence during this study period averaged 16.7%. An infection was presumed present based on swelling, heat, pain, drainage and positive bacterial culture where appropriate.
Abdominal procedure infection risk was highest at 28% possibly due to the length of an incision and the intestinal weight burden on the incision line. While many abdominal procedures result in contamination of the surgical area due to enterotomy or resection/anastomosis, in this study the meticulous surgical techniques minimized this as a risk.
The researchers identified specific factors that amplified the risk of a post-operative surgical site infection:
- Type of surgery.
- Repeat surgery ≤6 months in the same or nearby incisional approach, especially with an abdominal procedure: 38.1% infection rate compared to single surgery rate of 14.1%.
- Patient weight: There was a higher rate of infection for those 175 pounds heavier than those that did not develop infection, likely due to higher stress on the incision line with abdominal procedures.
- Gender and reproductive state: Incidence of infection in stallions was 2.3% compared to 16.1% in geldings, 24.3% in non-pregnant females, and 50% in pregnant mares.
- Duration of hospitalization: Horses with infection were hospitalized for an average of 21 days compared to eight days for those without infection. The longer stay had to do with ongoing treatment of SSI complications.
Another notable risk for infection relies on how well a horse recovers from anesthesia, with reports that a difficult anesthetic recovery might increase development of infection by four times, possibly due to increased bacterial contamination.
Abdominal procedure infection rate ranges from 7–37%, whereas arthroscopic surgery infection rate was less than 1% and overall infection frequency in all orthopedic procedures was around 10%.
A repeat laparotomy doubles the incidence of incisional complications. Added to this is the greater likelihood of incisional hernia and intestinal adhesions that develop subsequent to incisional complications.
Factors that seemed to amplify infection risk included:
- time of day
- season of surgery
- specific surgeon
- breed of horse
- age of horse, or
- performing a procedure on an infected anatomical structure.
Duration of the surgery did not have an association with infection incidence in this study, although many studies suggest that procedures longer than 90-120 minutes have higher infection rates.
The authors also noted that since this 2011-2013 study was done, surgical techniques and bacterial populations and bacterial resistance have changed, so new studies could shed more light on the current state of surgical site infections.