The deterioration of the liver function is an effective emergency that causes an acute liver failure (ALF). It is associated with some causes like neoplasia, toxemia, and infections. Portosystemic shunt is also a common cause in dogs and cats who can show signs of hepatic encephalopathy (HE). ALF should be recognized, and a correct intervention should be done as soon as possible, as this may quickly induce many severe alterations in every organ system (Dobratz et al. 2019). The most common signs in dogs and cats are anorexia, vomiting, diarrhea, PU/PD, lethargy to collapse, and/or abdominal pain. ALF could show alterations in all four cardiovascular, respiratory, neurological, and renal systems (Dobratz et al. 2019).
Cardiovascular Signs
Vasodilation associated with increased cardiac output, decreased vascular resistance, and decreased MAP is usual in animals with ALF. Due to these alterations, hypotension and hypovolemia are common and may get worse when the patient simultaneously shows vomiting and diarrhea (Dobratz et al. 2019). For this reason, it is mandatory to closely monitor HR, rhythm, cardiac contractility, blood pressure, and albumin. Albumin levels may be reduced when the liver already lost 70–80% of functionality (Mathews 2006).
Respiratory Signs
In cases of hypovolemia, acidemia, abdominal pain, or aspiration pneumonia, some respiratory signs, such as dyspnea, cyanosis, etc., may raise accordingly. Neurological changes may also impair respiration. It is essential, therefore, to protect the airways and promptly intubate. Assessing oxygenation/ventilation is of most importance (Dobratz et al. 2019).
Neurological Signs
Mentation is a parameter typically showing alterations and that may be quickly changed from depression to comatose or seizures. Hyperactivity, ptyalism, disorientation, circling, ataxia, muscular tremors, and conscious proprioceptive deficits are all signs that may be associated with HE. There are several factors that may lead to HE, such as SIRS, GI bleeding, hypokalemia, hyponatremia, diet change or indiscretion, furosemide treatment, azotemia, constipation, and alkalosis (Dobratz et al. 2019).
Renal Signs
Acute kidney injury (AKI) may occur early on ALF or even occur as signs of multiple organ failure. Due to high metabolic rate, liver, and kidneys may have signs of injury associated to many toxins (Dobratz et al. 2019). Every patient showing any alteration in one of the four systems should immediately have a vascular access and a minimum database, blood pressure, pulse oximeter, and ECG (Dobratz et al. 2019). ALF is assessed by means of specific diagnostic tests, which are as follows.
Albumin
Albumin levels are decreased when over 70–80% of liver function is lost (Mathews 2006). Changes in albumin levels lead to changes in intravascular colloid osmotic pressure (COP) which is an indicator of an eventual pulmonary oedema and mortality. Albumin is the main plasmatic protein produced in the liver by only 20–30% of the hepatocytes having a strong negative charge (Kirby, Linklater 2017). In case of acute liver failure, albumin will not be sufficiently produced, and consequently, patients have a higher risk of oedemas due to decreasing COP (Mathews 2006).
Blood Glucose
Deterioration of hepatic glycogen storage, hepatic insulin, and hepatic gluconeogenesis will induce hypoglycemia. This requires a decreased hepatic function of 70–80% and indicates a poor prognosis (Mathews 2006).
Electrolytes
Sodium (Na), chloride (Cl), potassium (K), calcium (Ca), magnesium (Mg), and phosphorus (P) are the main charged particles playing an important role in maintaining cellular functionality (Kirby, Linklater 2017). ALF may reveal hypo or hypernatremia, hypokalemia, and hypophosphatemia. Hyponatremia and hypernatremia may be indicators of a poor prognosis (Mathews 2006).
Coagulopathy
Determination of PT and aPTT may be easily done. PT reflects the function and quantity of extrinsic coagulation factors, while aPTT reflects the function and quantity of intrinsic coagulation factors (Kirby, Linklater 2017). These parameters are often increased in severe ALF. Spontaneous bleeding in patients with ALF indicates a poor prognosis with short survival period (Mathews 2006).
Red Blood Cells Status
In every critically ill patient, alterations in red blood cells and in hemoglobin are commonly seen. Liver disease may show a mild to moderate anemia or microcytosis (Mathews 2006). It is also important to perform a blood smear to assess RBCs morphology in order to identify the underlying cause of anemia. Spherocytes, micro and macrocytosis, hypo or hyperchromasia, anisocytosis, keratocytes, acanthocytes, echinocytes, presence of Heinz bodies are some of erythrocytes morphological alterations detected on blood smear (Kirby, Linklater 2017).
After the primary assessment of the patient with ALF, and in case of detection of the causative agent, the suitable antidote should be administered as soon as possible. A peripheral IV catheter placement is crucial, and some care shall be taken due to the high risk of bleeding after the venipuncture. Several patients with ALF have coagulopathy. Therefore, an appropriate pressure bandage should be applied on the site of IV catheter placement (Mathews 2006).
After the catheter placement, it is important to start a prompt fluid therapy plan. Avoiding fluids containing lactate is the best choice because this requires suitable liver function to be metabolized. Consequent dehydration may lead to poor perfusion, hypotension, and a lactate accumulation further contributes to the development of acidosis in these patients. On the other hand, alkalinizing fluids should be avoided in case the patient is alkalemic. In this case, 0.9% NaCl with potassium supplementation is recommended (Mathews 2006). However, the choice of the fluids is always dependent on the electrolytes and acid-base status of the patient being the states of hyponatremia, hypokalemia, and hypophosphatemia commonly seen in patients with ALF.
Acid-base alterations may be several. For example, patients with cirrhosis may have respiratory or metabolic alkalosis and, in terminal stages, may have metabolic acidosis (due to hypoxia and lactic acidosis). However, isotonic crystalloid fluids are generally used (Arnold 2018). In cases of HE, fluid therapy should include correction of hypokalemia and metabolic acidosis due to increasing ammonia, NH3 production, especially in cases of HE (Mathews 2006).
Hypoglycemia may rapidly develop, and when this is the case, its level should be monitored every 2–4 hours to avoid its consequent complications like seizure, collapse, weakness, or behavior changes (Mathews, 2006).
A correct nutritional support on patients with ALF is crucial, with a low-protein diet being recommended to decrease a substrate availability of intestinal NH3 production (Mathews 2006).
A good antibiotic therapy is always important, usually with ampicillin 10–20 mg/kg IV q 6–8 h in combination with enrofloxacin 5 mg/kg IV q 24 h until obtaining the bacterial cultures results. Since a gram-negative infection may lead to hypotension (Mathews 2006), an endotoxemia should be avoided.
Cerebral oedema is another complication in this clinical status. This is revealed from mental status alteration, mydriasis, delayed pupillary light reflex, and alteration on respiratory system.
Renal failure is another complication that may occur due to a tubular necrosis. A correct fluid therapy plan for avoiding hypotension, monitoring urinary output, and an appropriate treatment is always required.
As mentioned above, albumin levels may be decreased. Therefore, ascites is another common complication that may be shown. Abdominocentesis to relieve tamponade should be performed, being always cautious when removing large volumes of fluids for avoiding collapse and hypotension (Mathews 2006). It is well known that acute liver failure is a critical disease that deserves the best clinical attention and close monitoring.
As it is crucial to assess all the vital organ systems, as well clinical and laboratory parameters, and treatment goals, it is essential to assess each checking point. Thus, there are several auxiliary methods to help us on these patient monitorization. For example, the rule of 20 is a simple way to assess all the important checking points. In its simplest form, the rule of 20 is like a checklist for reminding doctors and critical care unit staff of all the details that are needed to be evaluated (Kirby, Linklater 2017).
References
1. Arnold CF, ed. Manual de Fluidoterapia en Pequeños Animales. Barcelona, Spain: Sant Cugat del Valles Multimedica ediciones veterinarias; 2018.
2. Dobratz K, Hoper K, Rozanski E, Silverstein D, eds. Textbook of Small Animal Emergency Medicine. Hoboken, NJ: Wiley Blackwell; 2019.
3. Kirby R, Linklater A. Monitoring and Intervention for the Critically Ill Small Animal—The Rule of 20. Oxford: Wiley Blackwell; 2017.
4. Mathews K. Veterinary Emergency and Critical Care Manual. Guelph, ON: Lifelearn; 2006.