IN-DEPTH: EMERGENCY AND CRITICAL CARE PROCEDURES


serum lactate). The increased reliance on perito- neal lactate has likely decreased the absolute need for availability of a hematology analyzer for perito- neal analysis. If the peritoneal lactate is greater than the peripheral lactate, one can usually feel fairly confident that some degree of bowel compro- mise is present.13 The difference in peritoneal: plasma lactate can vary depending on the clinical condition; but in cases of strangulating intestinal lesions, the peritoneal lactate is often 2–4 times that of the peripheral lactate. In the prospective study by Latson et al13, horses with strangulated small intestine had a lactate value of 8.45 mmol/L, com- pared with those with nonstrangulating obstruction 2.09 mmol/L. Although the usefulness of peritoneal fluid in the evaluation of the horse with acute colic has been well documented in the literature, it is important to remember that it can be associated with a few significant complications, such as enterocentesis (sometimes innocuous, sometimes not), or full- thickness laceration of bowel or spleen. Some cli- nicians feel strongly that the use of a teat cannula decreases the risk of complication. We have seen complications associated with all methods of abdom- inocentesis. As with any diagnostic procedure, it is important to consider the risks vs the benefits of the proposed intervention.


8. When to Refer/Indicators for Surgery


The fastest referrals, and indeed the shortest work- ups, are associated with the violently painful horse presenting for colic. Unrelenting discomfort that cannot be managed medically usually results in a relatively rapid progression to surgical intervention or euthanasia. Other indicators for referral might include moderate or severe hypovolemia, large amounts of gastrointestinal reflux, signs of physio- logic decline (increased heart rate, respiratory rate, increased lactate, abnormal mucous membrane color), or discomfort that persists despite adminis- tration of analgesics, even if it is not violent. In some cases, the signalment in combination with the presenting clinical signs might influence the deci- sion to refer; a 25-year-old gelding with a heart rate of 56 bpm and mild abdominal discomfort is much more concerning than a yearling with the same clin- ical findings. It is also important to distinguish between cecal and large colon impaction, as one might be more inclined to refer a horse with cecal impaction, depending on the owner’s feelings re- garding surgery. The decision for surgery is based on the compila-


tion of all components of the colic workup. Abnor- mal findings on abdominal palpation per rectum, such as thickened small intestine or palpable intus- susception, and peritoneal fluid that is serosangui- nous or has an increased lactate, are often indicators that surgery is required. Horses that fail to re- spond to medical management, despite aggressive intervention, and do not have salient evidence of


4 2016  Vol. 62  AAEP PROCEEDINGS


enterocolitis, might need an exploratory celiotomy to make a diagnosis. Surgery should at least be con- sidered, and discussed with the owners, in horses with cecal impaction/dysfunction, given that it is difficult to predict which will develop a cecal rup- ture. It is important to remember that timely re- ferral, thorough evaluation, and appropriately timed surgical intervention have likely been the greatest contributors to the improved prognosis for colic appreciated in the last 10 years.


9. When It’s Not Colic


One of the few areas in our hospital setting in which initial patient assessment approaches a protocol is the admission and workup of a colic patient. All members of our clinical team have been trained in the elements of the routine of “colic workup,” which we have reiterated in lectures, rounds, and talks. In many settings, and in fact in the case of most horses presenting with colic, adherence to a protocol can be quite useful. However, horses may demon- strate colic-like behavior and have a disease that is not of gastrointestinal origin, with specific etiologies varying based on geographic location and equine population. Occasionally these patients are inter- preted as “uncomfortable” or “painful” enough to warrant exploratory celiotomy; in some cases this could be contraindicated. Misdiagnosis or delay in treatment could negatively affect outcome. Common causes of “colic” behavior that is not as- sociated with malposition of gastrointestinal tract can include problems of neuromuscular, reproduc- tive, metabolic, or respiratory origin. Horses with rabies, exertional rhabdomyolysis, botulism, teta- nus, uterine artery rupture, hyperammonemia, and pheochromocytoma have all been presented for colic to our hospital. Careful attention to the history and details of the initial assessment by the referring veterinarian, as well as the description of the first signs observed by the owner, can be extremely use- ful in determining the cause of the clinical signs. Horses suffering from various toxicities can also dis- play signs that can be interpreted as colic, such as jimsom weed toxicosis, ingestion of Acer rubrum (red maple leaf), cantharadin toxicity, or adverse flu- phenazine reaction. It is safe to say that few of these patients would benefit from inadvertent ex- ploratory celiotomy, and a delay in treatment could certainly decrease chances of survival.


10. Conclusion


The referring veterinarian plays a critical role in the initial evaluation and referral of the horse with colic. Increased awareness and timely referral both play an extremely important role in improving the sur- vival of horses that require surgery. A thorough workup and appropriate compilation of all the avail- able information is important for all veterinarians evaluating horses with colic, in either a primary or referral setting. It is also important to remember that there are a variety of colic “imitators” that


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