The main concerns in treating the cat with severe liver disease are nutrition, fluid and electrolyte balance, hepatic encephalopathy, and coagulation disorders.
Oral feeding or feeding with the assistance of a pharyngostomy, esophagostomy or gastrostomy tube would be the ideal way to maintaining the patient so long as it is not vomiting. In the case of significant vomiting (more than twice/day), parenteral nutrition will have to be instituted. It is essential to provide an adequate caloric base to allow the cat to be maintained in an anabolic state. The required amount of calories needed per day (RER) can be computed using the formula where:
RER = 70 x (Body weight in kg)0.75 or
RER = 30 x (Body weight in kg) +70
This formula has to be adjusted for catabolism, dietary thermogenesis, and the presence of sepsis. The diet should contain good quality protein and must not be restricted unless hepatic encephalopathy, hyperammonemia, or ammonium biurate crystalluria are present. In the absence of vomiting the protein requirement can be met with most available prescription diets that contain high quality protein, adequate fat and carbohydrate along with adequate vitamins and minerals to meet the cat's daily requirements. If the cat is being tube fed the use of a blender will greatly facilitate its administration. Cats on enteral nutrition will be fed commercially available liquid diets that are made of the right consistency for enteral tube administration. It is important to start such diets slowly so that osmotic diarrhea is avoided.
Sodium intake should be limited to 100 mg/100 kcal energy requirement in hypoalbuminemic cats and in those with ascites. The palatability from such a diet will probably suffer, and in the cat that is already anorectic, tube feeding will probably be essential.
The critically ill cat can very likely become depleted of thiamine and vitamin B12. Thiamine deficiency can cause a severe polioencephalomalacia and is best avoided by providing normal daily needs. Thiamine hydrochloride injection (50-100 mg IM or SQ) should be given in any cat that is showing signs compatible with thiamine deficiency (starry-eyed gaze, fixed mid-position or dilated pupils, ataxia, dementia, and dysequilibrium. Fifty milligrams can be given daily for the next few days followed by normal dietary amounts. Vitamin B12 (cobalamine) supplementation might help cats with co-existing pancreatic and small intestinal disease. Blood cobalamine levels can be sent to a commercial laboratory and treatment can be provided with 0.5 to 1.0 mg of B12 IM or SQ every 7-21 days.
Vitamin E and Vitamin K1 are also important nutrients that should be provided for their activity against cellular oxidative injury and coagulation disorders, respectively. A recommended dose for Vitamin E is 10 units/kg/day. Vitamin K1 is necessary for the facilitation of Factors II, VII, IX and X and is dosed at 0.5 to 1.5 mg/kg sid-bid. It is important to remember that no vitamin injection should be given by IV push because it will likely cause an anaphylactoid reaction.
Fluid therapy and meticulous protocols for its administration is an essential part of caring of critical care medicine. Cats are very susceptible to having intravenous fluid overload and should therefore be monitored closely. The special considerations concerning fluid therapy for cats with liver disease include hypovolemia, hypoalbuminemia, blood loss, predisposition to edema and body cavity effusions, and sepsis caused by breaks in sterile procedure. The tendency for sensitivity to fluid overload is because the patient with chronic liver disease can have an active renin-angiotensin-aldosterone system because of the ineffective blood volume they might have. One good way to administer parenteral fluids to such patients is to infuse a slow infusion of both crystalloids and colloids. This can be done with alternating or combined delivery methods. The increased plasma oncotic pressure delivered with this fluid formulation will help restore intravascular Starling's forces to normal by expanding intracellular volume, limiting the requirement of crystalloid, and allowing for a more prolonged lasting effect of the volume expansion efforts. It is recommended that only one third of the normal amount of crystalloid be given if a colloid is given at a dose of 10/ml/kg, which is the 24 hour recommendation of Hetastarch for the cat. If either Hetastarch or Dextran 70 is used, it is important to consider their effect on the patient's coagulation status because of their known tendency to antagonize blood clotting which is already a concern in a cat whose liver disease is already compromising hemostasis.
Albumin infusions will benefit the patient with hypoproteinemia and when combined with rapid paracentesis on the ascitic cat, the procedure might avoid being complicated by life- threatening hypovolemia. Although human albumin has been given to several dogs without allergic complications, it might be safer to use plasma from another cat until more is known about the cat's ability to tolerate plasma proteins from other animal species. Any foreign protein carries the threat of anaphylaxis with it, thereby calling for much diligence during its administration. All allergic reactions must be met with immediate discontinuation of the plasma or albumin infusion. If necessary, parenteral epinephrine must be given at a dosage of 0.01 mg/kg IM and repeated in 20 minutes if anaphylaxis occurs.
Dextrose-containing solutions should be used whenever the blood glucose concentration cannot be maintained within normal limits of 70-125 mg/dl. Hyperglycemia can cause several complications including immune compromise thus predisposing to infection, osmotic diuresis with its attending loss of important electrolytes and water soluble vitamins, and a contributing factor to the formation of respiratory acidosis. However if hypoglycemia is present it should be countered with dextrose administration. Hypoglycemic encephalopathy should be treated immediately with dextrose injection at a dose of 0.5 gm/kg, which is met with 1.0 ml of 50% dextrose IV or 2 ml/kg 25% dextrose solutions. Intravenous injections of such hypertonic solutions must not be allowed to extravasate because of the extensive tissue sloughing that can occur.
The anemia that occurs with liver disease can be uni- or multifactorial. Blood loss can occur from slow bleeding gastric ulcers, especially if mast cell cancer is the cause of the liver disease. Liver disease alone has been associated with gastric ulcers. Other causes can be the anemia of chronic disease or that due to any co-existing disease such as feline leukemia virus. Lastly and by no means least, iatrogenic blood loss will occur from too frequent phlebotomies. When anemia is expected, a donor should be identified, cross-matched, and be readily available when needed. The anemia of chronic disease might even benefit from Epogen treatment, but here again judicious use is important in order to avoid autoimmune destruction of the cat's red blood cells.
This is a critical part of treating any cat with severe liver disease. The major strategies include avoiding the onset of hypokalemia or metabolic alkalosis; treating GI bleeding vigorously and expediently; maintaining normal blood pressure; avoid protein administration; and maintain normal fluid, pH and serum electrolyte balance.
Adjusting enteric bacterial flora is sometimes necessary and this can be brought about by several different methods. Neomycin or metronidazole can be given orally in order to remove the bacteria that are producing ammonia within the intestinal lumen. Retention enemas containing neomycin and saline in a proportion of 7:1 can also be used if the cat is comatose or where oral medication is otherwise restricted, as occurs with severe vomiting. Lactulose solution can also be used to adjust the bacterial flora through its ability to maintain an acidic environment within the lumen of the colon thereby preventing the conversion of ammonium to the more absorbable ammonia.
General Patient Care
Any care delivered to cats should always include measures that consider their species requirements for gentle handling, minimal restraint, and measures taken to keep them as clean as possible. Baths should be given to remove any soiling from feces or urine. All catheters should be inspected for potential sites of contamination or underlying skin inflammation and any such occurrences should be managed as soon and as appropriately as possible. Any medications that are not necessary should be omitted and care should be taken to avoid drug interactions. Intravenous catheter sites should ideally be rotated every 3-4 days, but because of the logistical difficulties encountered with the cat being such a small species, many intravenous catheters can be retained for as long as 7 days without consequence, but under such conditions extremely meticulous catheter care is essential.