BACK TO BASICS: THE ACUTE ABDOMEN IN THE FIELD


phate, it also results in thirst and hypocalcemia, making magnesium sulphate preferable.8 Access to feed should not be permitted but water should be freely available. For impactions that persist, ag- gressive enteral and/or intravenous fluid therapy should be instituted. One study demonstrated the increased efficacy of continuously administered en- teral rehydration solution in softening colonic con- tents as compared with intravenous fluids, which are probably best suited to restoring the systemic extracellular fluid compartment.9 In another study, investigators determined that administration of 8–10 L of isotonic enteral fluids every 2 hours in horses with either large colon impaction or large colon displacement successfully resolved impactions in 99% of cases and in excess of 80% of large colon displacements within 24-hours. The enteral fluid was practically simple to make, using6gNaCland 3 g KCl/ L of tap water. made from water and electrolytes. In some cases, a less aggressive ap- proach (5Lq2–4 hours) is helpful to reduce impac- tions without causing colic or reflux associated with over-filling the stomach. If the impaction remains unresolved, the horse becomes uncontrollably pain- ful, or extensive gas distention of the colon occurs, surgery is indicated.


8. Considerations for Fluid Therapy


Intravenous fluid therapy is typically more practical to reserve for referral hospitals because of the need for frequent monitoring by a knowledgeable techni- cal staff. It is certainly possible to administer flu- ids in the field, but the time taken to place a catheter and a therapeutic volume of fluids should be care- fully considered. Occasionally, catheter placement is also reasonable to enable horse owners to repeat treatment during shipping, particularly for a recur- rently painful horse that has a long shipping time. For IV fluid therapy, once the degree of dehydration has been estimated, the percentage is multiplied by the horse’s body weight to give the fluid deficit (e.g., 6% dehydration  500 kg  30 L). In the field, if fluids are going to be administered, the veterinarian should be prepared to give approximately 15–20 L, which corresponds to half the fluid deficit for an adult horse that is 6% to 8% dehydrated. This avoids any misconception by the owner that a small volume of fluids will make a difference.


9. Conclusions


Important considerations for optimal treatment of colic in the field are optimal use of available analge-


sics based on their potency and duration of action, as well as a knowledge of how well the horse can be monitored by the owner. Other considerations are the indicated usages of nasogastric laxatives, and the place of rehydration therapy. Importantly, field analgesia and fluid therapy are effective in the large majority of horses with colic. However, for those horses with breakthrough pain, particularly after potent analgesics including alpha-2 agonists (xylazine and detomidine) and opiates (butorphanol) should be carefully considered for referral. Addi- tionally, management of pain but a lack of success at resolving conditions like large colon impactions over 1–2 days should be also be considered for referral.


Acknowledgments


Declaration of Ethics The Author has adhered to the Principles of Veteri- nary Medical Ethics of the AVMA.


Conflict of Interest The Author has no conflicts of interest.


References and Footnote


1. Sellon DC, Roberts MC, Blikslager AT, et al. Effects of con- tinuous rate intravenous infusion of butorphanol on physio- logic and outcome variables in horses after celiotomy. J Vet Intern Med 2004;18:555–563.


2. van Loon JP, Van Dierendonck MC. Monitoring acute equine visceral pain with the Equine Utrecht University Scale for Composite Pain Assessment (EQUUS-COMPASS) and the Equine Utrecht University Scale for Facial Assessment of Pain (EQUUS-FAP): A scale-construction study. Vet J 2015;206: 356–364.


3. Gleerup KB, Forkman B, Lindegaard C, et al. An equine pain face. Vet Anaesth Analg 2015;42:103–114.


4. Morresey PR, White GW, Poole HM, et al. Randomized blinded controlled trial of dipyrone as a treatment for pyrexia in horses. Am J Vet Res 2019;80:294–299.


5. Proudman CJ, Dugdale AH, Senior JM, et al. Pre-operative and anaesthesia-related risk factors for mortality in equine colic cases. Vet J 2006;171:89–97.


6. Blikslager A. Managing pain associated with colic. Comp Contin Educ Pract Vet 2008;30:294–307.


7. Hardy J, Bednarski RM, Biller DS. Effect of phenylephrine on hemodynamics and splenic dimensions in horses. Am J Vet Res 1994;55:1570–1578.


8. Lopes MA, White NA 2nd, Donaldson L, et al. Effects of enteral and intravenous fluid therapy, magnesium sulfate, and sodium sulfate on colonic contents and feces in horses. Am J Vet Res 2004;65:695–704.


9. Lopes MA, Walker BL, White NA 2nd, et al. Treatments to promote colonic hydration: Enteral fluid therapy versus intra- venous fluid therapy and magnesium sulphate. Equine Vet J 2002;34:505–509.


aBuscopan®, Boehringer Ingelheim Animal Health, Ltd., Du- luth, GA 30096.


118 2020  Vol. 66  AAEP PROCEEDINGS


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