Alpha2 Agonists and Sedatives Myths The ability of xylazine to reduce intestinal blood flow and motility could be of clinical importance in impaction colics. This is untrue and xylazine might relieve spasm, which could help with removal of the impaction. Also the motility effect is short-lived.
This demonstration fails because the oil in the colon does permeate colon contents under the massaging effect of abdominal contractions during breathing and other activities in the live horse. Also at surgery, oil can be found deep within the impacted mass. Water might be absorbed by the colon and not reach the impaction in the volume infused. 2. Mineral oil should not be given to a horse that might go to surgery because it increases the risk of contamination and peritonitis if the intestine has to be opened. This is untrue because current methods for emptying the colon are very effective and clean.
Opioid Analgesics 1. Butorphanol (Torbugesic, 0.02 to 0.08 mg/kg IV) is usually used with xylazine. 2. At recommended doses, side effects include inhibition of motility. 3. The duration of effect is short and its effects on motility Magnesium Sulfate 1. Magnesium sulfate is classified as a saline laxative, appear to be site and dose-dependant. assumed to increase fecal bulk and water content 4. Side effects can be minimized by continuous infusion through an osmotic response to the poorly-absorbed of 23.7 μg/kg/hr, after a loading dose of 17.8 μg/kg. magnesium ion. 5. Morphine or meperidine should only be used in ex2. Magnesium sulfate at a dose of 1 mg/kg (1 lb to a 1000 treme cases. lb horse) reflexly stimulates equine colonic function, possibly through the gastrocolonic reflex. Laxatives 3. Can be given once or twice daily for 23 days with little Laxatives should be given every 12 hours. Sometimes, risk of a toxic effect. reflux through the stomach tube makes it impossible to give 4. Repeated doses can cause weakness, collapse, and laxatives and can signify another problem or a longstanding tachycardia from the absorbed magnesium ion, espeimpaction (check for gastric reflux before giving any laxacially if it is administered with DSS (see below). tive). The horse colon accounts for a greater proportion of its 5. Treatment of toxicosis is diuresis with IV fluids and total body weight than does the human colon, and so human IV calcium. doses for laxatives on a body weight basis are underdosing for horses. However, increasing the dose, increases toxicity. Dioctyl Sodium Sulfosuccinate Facts 1. DSS is an anionic surfactant that has been classified Mineral Oil Facts as a wetting agent, irritant laxative, or fecal softener. 1. Mineral oil (half to 1 gallon to a 450 kg horse) is an 2. DSS can increase mucosal permeability (increases Mg effective fecal softener. absorption if given with magnesium sulfate), cause 2. Its presence on the perineum, tail, and hind limbs, surface damage and inflammation. usually 12 to 24 hours after administration, indicates that the intestinal tract is partly or completely patent. Dioctyl Sodium Sulfosuccinate Myth DSS is an effective fecal softener. 3. Mineral oil can pass around some obstructions without In one study in horses, DSS was ineffective as a laxative and softening them. 4. Mineral oil has been advocated as a cathartic in cases caused mucosal injury at the recommended dose. of intoxication. However, its use in cases of cantharadin toxicity may be contraindicated because it can Psyllium Hydrophilic Mucilloid Facts 1. Psyllium hydrophilic mucilloid is a bulk laxative used increase the absorption of cantharadin. to remove or prevent a sand impaction. 5. Careful attention must also always be paid to place2. The dose is 1 g/kg or 500 g in 6 to 8 L of water through ment of the nasogastric tube prior to delivery, as dea nasogastric tube 2 3 times daily. position of mineral oil in the lungs can cause a fatal 3. Difficult to administer because it has a tendency to gel. lipoid pneumonia. 4. When fed routinely (50-100g daily), fermentation of psyllium by intestinal bacteria produces short-chain Mineral Oil Myths fatty acids that might benefit healing of the colonic 1. Despite its routine use, there is little literature evidence mucosa in horses with right dorsal colitis. to support the use of mineral oil in horses. Mineral oil will lubricate ingesta but does not penetrate an impaction the same way that water does. This can be Psyllium Hydrophilic Mucilloid Myths There is conflicting evidence as to efficacy of psyllium on demonstrated with fecal balls immersed in water or the feed on a daily basis to prevent sand impaction or given mineral oil in fecal cups overnight. The water penby stomach tube to remove a sand impaction. Of twelve etrates the feces; oil does not. 30 The Practitioner Issue 1 • 2017