Portosystemic shunt in dogs and cats (Proceedings) - Veterinary Healthcare
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Portosystemic shunt in dogs and cats (Proceedings)


CVC IN KANSAS CITY PROCEEDINGS


Treatment

Surgery is recognized as the treatment of choice for PSS. Because liver needs hepatotrophic substances from portal blood flow, deterioration of liver function can be expected if the shunted blood flow is not surgically corrected in a physiologic direction. Medical treatment will not correct this alteration, therefore long term survival is not expected. In one study, only 2 of 8 dogs with medical treatment were still alive at 6 months. Life expectancy of 2 months to 2 years is generally reported; the actual time presumably being dependent on the amount of portal blood flow. Restoring the flow of hepatotrophic substances to sinusoidal milieu results in substantial hepatic regeneration and reversal of functional impairment.

Medical treatment

Pre-operative medical treatment is used to decrease acute signs of hepatic encephalopathy (coma, seizure, abnormal behavior) resulting in a patient in better condition for anesthesia and surgery. The goal of medical treatment is to decrease production of ammonium and its absorption from the intestine. Patients presenting with seizures or coma require emergency treatment including: fluid therapy, betadine enema, oral neomycin (20 mg/kg) or metronidazole (7.5 mg/kg three-times a day) and oral lactulose when oral administration is feasible. Dehydration should be treated aggressively as azotemia can aggravate the encephalopathic state by increasing intestinal production of ammonia. Replacement fluids using 0.45% NaCl with 2.5% dextrose is recommended. Animals with liver disease tend to become hypoglycemic and retain sodium. Benzodiazepin or barbiturate to control seizure should be used with caution because of increase drug sensitivity. Mannitol (0.5 mg/kg IV) can be used to reduce intracranial pressure. Electrolyte disorders and acid base imbalance should be corrected as needed according to biochemical profile. All oral intake of food is stopped for 24 to 48 hours. Betadine enema and antimicrobial therapy decrease colonic bacterial flora. Once the animal is stabilized and improving chronic treatment for HE should be instituted and surgery planned. Antimicrobial therapy and lactulose decrease ammonia production by decreasing colonic flora. Lactulose acts by acidifying intestinal content thus reduces absorption of ammonia, decreases transit time, and reduces colonic bacterial population. The dose of lactulose used is extremely variable: 2.5 ml to 25 ml three time a day in a dog. Protein restricted diet is required to reduce the amount of ammonia in the intestine.| The ideal diet should be: highly digestible (little residue reaches the colonic bacteria), contain high biological value protein (high levels of branched chain amino acids and arginine and low levels of aromatic amino acids and methionine), and have a highly digestible carbohydrate as the primary source of calories. Protein content should be 14 to 17 % for the dog and 30 to 35 % for the cat.

Surgical treatment

Patients with PSS experience a reduction in absorption, metabolism, and clearance of drugs due to liver impairment. Fentanyl can be used for sedation. Mask induction with isoflurane followed by endotracheal intubation is the method of choice. Dextrose (2.5%) is important during surgery and the immediate postoperative period to maintain blood glucose. Cephalosporin perioperatively is recommended. Ischemic episode can occur in the bowel during manipulation of the PSS that will may result in bacterial embolization.


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