BACK TO BASICS: THE ACUTE ABDOMEN IN THE FIELD


horse has been referred, time is again of the essence to decide on whether or not a horse should go to surgery in order to improve long-term outcome. Once in surgery, the surgical team should be able to move swiftly through an exploratory and any surgi- cal manipulations required within 2–3 hours. This should aim to maximally reduce time in the abdo- men, which translates to trauma, systemic inflam- mation, and a poorer long-term outcome. Of all of the long-term complications hindering a good long-term outcome, adhesions are among the most problematic. These result both from the level of intestinal injury induced by the obstructive disease process and the level of manipulation at surgery. Another aspect of colic surgery that is critical to long-term outcome is closure of the incision. That is because in one study, one of the factors that lim- ited long-term outcome to the greatest extent was abdominal hernias.4 These likely relate to closure technique and whether or not the incision becomes infected. Infection rates tend to be up to20% at most surgical hospitals,5 but should be monitored closely to make sure the prevalence is not increas- ing. An additional factor that likely has a role in incisional complications is trauma to the incision itself, which also relates to time and technical pro- ficiency of the surgical team.


4. Post-Operative Complications


The initial objective following surgery is a satisfac- tory recovery from anesthesia. Although cata- strophic injuries during anesthetic recovery, parti- cularly fractures, have become more uncommon with advances in anesthetic techniques, nonethe- less, colic patients that present with systemic com- promise are at increased risk of complications, particularly following a long surgery for procedures such as a resection. Beyond anesthetic recovery, there are three major life-threatening complications of colic surgery that should be discussed with own- ers. First, assuming the horse recovers well from anesthesia, there is management of shock states (hypovolemia and endotoxemia [sepsis or systemic inflammatory response syndrome]). This includes optimal fluid and electrolyte administration, judi- cious use of non-steroidal anti-inflammatory drugs (NSAIDs), use of pain medications to optimize recov- ery,6 and use of colloids or plasma as needed to maintain oncotic pressure. Medications to specifi- cally target endotoxemia, such as polymyxin B (5,000 u/Kg, IV),7 may be helpful, but remain largely unproven by clinical trials.8 The next phase of post-operative management tends to be post-opera- tive ileus (POI). There is reasonably good evidence that early return to feeding reduces POI.9 Aside from this principal, for horses that do develop POI, current treatment includes continued use of anti- inflammatory drugs and intravenous (IV) lido- caine.10 Studies have shown that COX-2 inhibitors may be more beneficial than non-selective NSAIDs because they are capable of managing pain without


inhibiting intestinal repair.11,12 Interestingly, con- current use of IV lidocaine (1.3 mg/kg loading dose, 0.05 mg/mL controlled rate infusion [CRI]) also im- proves intestinal repair.13 There has also been one clinical trial showing that IV lidocaine reduced the length of time of POI and amount of reflux,14 but more rigorous clinical trials are needed to discern the utility of IV lidocaine. The latter phase of post- operative management in the hospital tends to re- late to adhesion formation, particularly in patients treated for small intestinal obstruction. Develop- ment of adhesions are thought to be clinically evident based on recurrent episodes of colic in at-risk pa- tients.15 One intra-operative treatment that is be- lieved to reduce onset of adhesions, based in a reduction in incidence of post-operative colic in pa- tients following small intestinal surgery, is car- boxymethylcellulose,15 which can be used during surgery and following lavage of the abdomen with sterile saline in volumes of 500 mL to 1 L. In ad- dition, post-operative peritoneal lavage and drain- age has been found to mitigate adhesion formation in an experimental setting,16 and can be used clini- cally by infusing 10 L balanced polyionic fluids into an abdominal drain, and retrieving these fluids after allowing approximately 20 minutes of time within the abdomen. There are also other post-operative complications


that occur less frequently, including laminitis, which can be devastating. A relatively recent advance in treatment of laminitis has been the use of digital cryotherapy (continuous icing of the feet) in any horse at risk of laminitis,17 and this may improve long-term results. Importantly, a great deal of at- tention should also be paid to the midline incision. Incisional infection remains a relatively common post-operative complication, and in some cases is associated with hernia formation. Incisional infec- tions are resolved by early removal of skin staples or sutures to allow for drainage, and lavage of the incision. Horses may continue to have clinical evi- dence of an incisional infection at the time of dis- charge, which will need to be attended to by the referring veterinarian. The incision will need to be carefully probed to determine the extent of infection, including whether or not the sutures within the linea alba are prematurely breaking down. If there is a concern that a hernia may develop, commercial hernia belts are recommended to reduce tension on the linea alba. Once a hernia has formed, it can be monitored ultrasonographically and decisions can be made as to whether to ultimately perform herni- orrhaphy. Unfortunately, the best time to take these horses back to surgery is after the incision has healed to the greatest extent possible, forming a sufficient thickness of fibrous tissue to optimize the repair, at approximately 6 months following sur- gery. This can be very difficult for owners to un- derstand, and can require a lot of additional communication between the veterinarian, surgeon, and owner.


AAEP PROCEEDINGS  Vol. 66  2020 125


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