72 Scientific Reports: Original Study JAVMA, Vol 219, No. 1, July 1, 2001 EQUINE P ostoperative ileus (POI) is a common and serious complication of surgery for equine colic. The clini- cal signs of POI include signs of abdominal pain, absence of gastrointestinal sounds, absence of defeca- tion, and nasogastric reflux or accumulation of stom- ach fluid that can be evacuated via nasogastric tube. Horses with POI require intensive medical manage- ment including fluid therapy and frequent drainage of gastric contents. The consequences of POI are costly, both in terms of morbidity and mortality to the horse and expense to the owner. The mortality rate among horses with POI may reach 86%, and POI ranks first among fatal postoperative complications of horses with colic, accounting for up to 43% of deaths. 1 The pathogenesis of equine POI is unknown, but results of experiments in horses and other species sug- gest that inflammation, sympathetic stimulation, and endotoxemia likely play a role. 2-5 The role of inflamma- tion has been revealed by experiments in which manip- ulation of the bowel of rats resulted in leukocyte infil- tration of the smooth muscle, which was accompanied by slower transit times and decreased in vitro contrac- tility of intestinal smooth muscle. 6 The role of sympa- thetic stimulation in POI in rats is indicated by the pre- vention of POI by chemical sympathectomy. 7 Although bowel manipulation models of POI have been used in horses, the specific mechanism through which ileus was induced was not determined. However, in addition to inflammation and sympathetic stimulation, endo- toxin may play a role in spontaneous POI of horses, because endotoxin reduces intestinal motility. 5 Treatment and prevention of POI is usually target- ed at reversing or preventing one of the pathophysio- logic mechanisms or directly stimulating the gastroen- teric smooth muscle by use of prokinetic drugs. In a previous study, 8 21% of horses with colic that required surgery developed POI, by the investigators’ definition. In that study, the survival rate was 95% in horses with- out POI, compared with 83% in horses with POI. High PCV, high pulse rate, high plasma glucose concentra- tion, and small intestine lesions were identified as risk factors for POI. The purposes of the study reported here were to evaluate the incidence of POI in a hospital population and identify factors associated with increased risk of POI. Materials and Methods Selection of case horses and control horses—Records of all horses that were admitted to the Texas Veterinary Medical Center for colic and underwent surgery between Jan 1, 1990 and Dec 31, 1996 were reviewed. Horses that did not survive surgery (ie, horses that were euthanatized during anesthesia or died during surgery), were < 1 year old, or were American Miniature Horses were excluded. The rationale for excluding horses that were < 1 year old was 2-fold. First, in our experience, causes of colic in foals and weanlings differ from those of horses that are ≥ 1 year old. Second, because body size of these younger horses was smaller, compared with older horses, nasogastric reflux volume would be diffi- cult to compare directly with that of larger horses; this also was the rationale for excluding American Miniature Horses. Postoperative ileus was defined as nasogastric reflux volume > 20 L during a 24-hour period after surgery or reflux volume > 8 L at any single sampling time after surgery. Control horses did not develop POI, whereas case horses did. Data collection—For each horse, only data for the first colic episode that required surgery were included (ie, data were not included for repeat celiotomy or subsequent admis- sions for surgery for colic during the study period, but the occurrence of an ensuing celiotomy was recorded). All hors- Risk factors associated with development of postoperative ileus in horses Allen J. Roussel Jr, DVM, MS, DACVIM; Noah D. Cohen, VMD, PhD, DACVIM; R. Neil Hooper, DVM, MS, DACVS; Peter C. Rakestraw, VMD, DACVS Objective—To determine risk factors associated with development of postoperative ileus in horses under- going surgery for colic. Design—Case-control study Animals—69 horses that developed ileus after surgery for colic and 307 horses that did not develop postoperative ileus. Procedure—Signalment, history, clinicopathologic data, treatment, lesions, and outcome were obtained from medical records. Results—Variables associated with increased risk of postoperative ileus included age > 10 years, Arabian breed, PCV ≥ 45%, high serum concentrations of pro- tein and albumin, anesthesia > 2.5 hours’ duration, surgery > 2 hours’ duration, resection and anastomo- sis, and lesions in the small intestine. Enterotomy reduced the risk of postoperative ileus. After multi- variate logistic regression, the final model included the variables Arabian breed, PCV ≥ 45%, lesion type, duration of surgery (> 2 hours vs < 2 hours), and pelvic flexure enterotomy. Conclusions and Clinical Relevance—Results sug- gest that by evaluating certain factors, horses at increased risk of postoperative ileus may be recog- nized before the condition develops. Preventative treatment and early intervention may be instituted in these horses. Shortening surgery time and perform- ing an enterotomy may decrease the probability of horses developing postoperative ileus. (J Am Vet Med Assoc 2001;219:72–78) From the Department of Large Animal Medicine and Surgery, Texas A&M University, College Station, TX 77843. Funded by the Patsy Link Equine Research Endowment. Presented in part as an abstract at the American College of Veterinary Internal Medicine Forum in Seattle, Wash, June 2000. The authors thank Alicia Bye, Jason Hicks, Cal Davis, Jodi Baxter, Kim Jackson, and Ryan Lee for technical assistance. Unauthenticated | Downloaded 10/31/24 05:11 AM UTC