Stabilizing the Surgical Colic Patient for Referral

CHAPTER 84 Stabilizing the Horse with Surgical Colic for Referral



Lance H. Bassage, II


An acute, severe gastrointestinal crisis, or “colic,” is arguably the most common potentially life-threatening condition encountered by equine practitioners. It is also invariably accompanied by a considerable degree of anxiety and emotional distress on the part of the owner and other individuals tending to the horse. For these reasons, it is imperative that the attending veterinarian be able to think and act clearly, expediently, competently, and with compassion during the diagnosis and emergency management of such cases. To that end, it is incumbent on the practitioner to have a well-organized, logical, and thorough therapeutic approach tailored to each horse’s clinical status and any existing logistic challenges before referral to a surgical facility.



TIMING IS EVERYTHING


Improvements and innovations in surgical techniques and postoperative care over the last two decades have contributed to an appreciable increase in the success rate for horses that undergo surgery for colic. However, there is little doubt that the condition of the horse at admission to the surgical facility remains the single most important variable in the equation for a successful outcome, assuming that the facility and personnel are able to provide appropriate care for such patients. With that in mind, it cannot be overemphasized that, more than anything else, prompt referral is of paramount importance to a successful outcome. Early recognition that a horse has or is likely to have a surgical lesion, and frank, unambiguous discussions with the owner or agent regarding the potential severity of the condition and need for referral to a surgical facility are key steps in the process. Control of clinical signs and supportive care measures provided before referral should be medically appropriate for the clinical status of the horse but should not unduly delay transport.



INDICATIONS FOR SURGERY


It is beyond the scope of this chapter to address in detail the various types of surgical lesions affecting the gastrointestinal tract in horses, the diagnostic techniques used in the workup of these cases, or implications of various findings. However, in light of the importance of prompt identification of the horse that will require surgery for resolution of surgical colic, a short discussion of diagnostic findings that are strongly suggestive of or highly consistent with surgical lesions is warranted.



Physical Examination


Above all else, signs of severe abdominal pain, in particular pain that is unresponsive or only transiently responsive to moderate to high doses of appropriate analgesics or sedative-analgesics, are in and of themselves a hallmark finding of a potential surgical problem. This is particularly true if gastric decompression fails to provide sustained pain relief or if findings on rectal examination are also consistent with a surgical lesion. Other strong indicators on physical examination and in no particular order of importance include persistent, moderate tachycardia (HR ≥50 beats per minute) despite an adequate period of time having passed for response to symptomatic and supportive care; severe tachycardia (HR ≥80) in the absence of signs of blood loss; abdominal distension; absence of auscultable borborygmus throughout the abdomen; abnormalities of the mucous membranes, including pallor, extreme hyperemia, or progression toward dark red-purple coloring in the absence of strong signs of enterocolitis; and markedly prolonged capillary refill time.



Nasogastric Intubation


Gastric reflux fluid, either exiting the nares spontaneously or obtained via nasogastric tube, should be regarded as an indication of a potential surgical problem such as primary small intestinal obstruction or impingement of the duodenum by a distended colon segment. Gastric reflux fluid that increases in volume or that is not retrieved until the horse has been evaluated several times is more compatible with a surgical lesion than with duodenitis-proximal jejunitis (i.e., anterior enteritis). Similarly, persistence of pain and a high heart rate or short-lived improvement in these variables following gastric decompression is compatible with a surgical lesion, whereas sustained remission of signs of colic with possible mild depression is more typical of horses with duodenitis-proximal jejunitis.



Rectal Examination


Abnormal rectal examination findings compatible with a potential surgical problem include small intestinal distension unaccompanied by large volumes of gastric reflux or associated with failure of gastric decompression to provide sustained pain relief or reduction in heart rate; moderate to severe large colon or cecal distension with gas, fluid, or digesta (particularly if accompanied by findings that suggest the affected bowel is coursing in an abnormal direction or is located in an abnormal position); progression in degree of distension on successive rectal examinations; and taut taenia or bands of mesentery to which transrectally applied manual tension elicits a painful response. Any horse with a cecal impaction—regardless of concurrent clinical signs—should be considered a potential surgical case, given the propensity for insidious progression to viscus rupture with this condition.



Other Findings


When time and equipment are available to pursue additional diagnostic testing, abnormal findings that are suggestive of or more compatible with a surgical condition include distended nonmotile small intestine visible during transabdominal sonography; sonographic evidence of mural thickening of the small intestine corresponding to vascular congestion; and serosanguineous peritoneal fluid, although not highly sensitive or specific, clearly suggests that bowel is inflamed or congested and possibly compromised and constitutes further impetus to consider referral without hesitation. In my opinion, a peritoneal fluid sample is rarely required in the field to determine whether a horse should be referred to a surgical facility. Abdominocentesis is most important for ruling out or confirming rupture of the gastrointestinal tract or when further evidence is necessary to convince a reluctant owner that the horse should be referred without hesitation if this is an option they are willing to pursue.


The preceding list is not intended to be entirely inclusive or exclusive. Gray areas almost always exist, particularly in horses with nonstrangulating obstructions such as impactions or simple displacements. In virtually all horses with a surgical lesion, some combination of these abnormalities is detected. The practitioner ultimately incorporates any or all of the diagnostic findings and, on the basis of experience and judgment, reaches a conclusion about the likelihood and severity of a surgical problem.



WHEN IS IT TOO LATE?


Every practitioner will be confronted with a severely compromised horse with colic, one for which the prognosis for survival is poor, if not grave, regardless of treatment or owner willingness to undertake heroic efforts. Horses with such conditions are those with gastrointestinal tract rupture or with extensive, severe bowel compromise such that associated endotoxemia, peritonitis, or concurrent cardiovascular derangements will be fatal.


Signs consistent with this situation include some combination of dark red to purple mucous membranes, profuse sweating, and trembling or shivering; heart rate greater than 100 beats per minute and progression from signs of severe pain to a state of calm distress with eyes glazed and altered mentation. Laboratory testing in such horses may reveal severe leukopenia (white blood cell count below 2000/μL) and severe hemoconcentration (packed cell volume greater than 60%), which are hallmark findings of impending death. In instances of viscous rupture, peritoneal fluid samples will be grossly brown to green, cloudy, and may have a fetid odor. This assumes that inadvertent enterocentesis has not occurred.



CLIENT COMMUNICATIONS

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May 28, 2016 | Posted by in EQUINE MEDICINE | Comments Off on Stabilizing the Surgical Colic Patient for Referral

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