L-ornithine L-aspartate in Overt Hepatic Encephalopathy

A. Introduction and Review of literature

Hepatic encephalopathy (HE) is broadly defined as an alteration in mental status and cognitive function occurring in presence of liver failure. The clinical picture of HE arises as a complication of chronic and, more rarely, acute liver disease. HE occurs in up to 70% of patients with cirrhosis at some time during the course of their disease (1,2). It is characterized by personality changes, intellectual impairment and a depressed level of consciousness. HE may be clinical unapparent (minimal HE) detected by abnormal neuropsychometric or neurophysiological tests (3). The common presentation is overt HE which occurs in patients with advanced cirrhosis with portal-systemic collateral circulation. Episodes of HE in patients with cirrhosis are induced by precipitating factors, like dehydration, hypokalemia, large protein intake, gastrointestinal bleeding, constipation, infections, use of psychotropic drugs, alcohol intake or acute liver injury (hepatitis).

Pathogenesis of hepatic encephalopathy In patients with liver cirrhosis, increasing structural replacement of hepatocytes with connective tissue leads to the loss of functioning hepatic parenchymal tissue and a reduction in the detoxification capacity of the liver. In addition, developing portal hypertension leads to the formation of a collateral circulation through which non-detoxified blood can by-pass the liver to reach the systemic circulation. Both these mechanisms contribute to the neurotoxins present in portal vein blood reaching the brain via the systemic circulation. A number of neurotoxins have been implicated in the pathogenesis of HE with ammonia being the most important (4,5). Fundamental conceptual advances in our understanding of hepatic encephalopathy have confirmed the central role of ammonia in the pathogenesis of portosystemic encephalopathy. Ammonia disrupts the function of neurones and astrocytes, giving rise to the symptoms of hepatic encephalopathy.

Classification/Grading of HE can be classified as type A (in Acute Liver Failure), B (in Portosystemic shunts without intrinsic liver disease) and C (patients of cirrhosis with portal hypertension/or portosystemic shunts) (5,6). In cirrhotics, the type C HE is further classified into Episodic, Persistent and Minimal HE. Chronic persistent overt HE patients are those who can be relatively stable with little day to day fluctuation in their mental status. Episodic (Unstable) HE patients are defined as those who were previously stable, but who over hours and possibly days develop clinically discernible features of HE, requiring medical attention and hospitalization. Minimal HE is clinically inapparent and detected by abnormal neuropsychometric or neurophysiological tests (3).

A precise gradation of HE is essential to prognosticate and plan an appropriate approach to treatment. According to the severity, HE has been traditionally divided into four stages based on alterations in the state of consciousness, intellectual function, behaviour, and neuromuscular signs (West Haven scale) (5).

A new classification has been recently proposed called the SONIC classification (7). This was necessary because the differentiation between minimal and Grade I HE is not reliable, but there is good inter-rater reproducibility in the identification of Grade II HE. It was suggested that patients with minimal HE and Grade I HE should be grouped together. It stresses that worsening cognitive function is continuum rather than categorical as emphasized in the Vienna 11th World Congress. It classifies patients with cirrhosis as being unimpaired and impaired neurocognitive function. Impaired cognitive function is subdivided into Covert HE (Minimal HE and Grade I HE) and Overt HE (Grades II-IV). It is thus inclusive of the West Haven criteria, yet emphasizes continuity as opposed to being categorical. The neurocognitive function of impaired, unstable patients can fluctuate from acute confusional syndrome to coma (Grades I to IV). They are the so called Type C- episodic HE patients.

Therapy of hepatic encephalopathy The main objective of therapy of HE is to (a) decrease intestinally derived toxins produced by excessive bacterial activity and decrease ammonia production or (b) increase ammonia detoxification (1,2,8,9).

1. Decrease ammonia production:

Enteric production of ammonia can be decreased by non-absorbable disaccharides such as lactulose or lactitol and non-absorbable antibiotics such as rifaximin. Lactulose/lactitol pass through the small bowel undigested. In the colon, bacteria degrade lactulose to various organic acids (e.g. lactic acid, acetic acid) with subsequent lowering of colonic pH. The mode of ammonia lowering may involve bacteriostatic effects, cathartic effects, or enhancement of conversion of ammonia to ammonium with excess hydrogen ion. Presumably ammonium is then excreted into the feces and eliminated (9, 10). Lactulose remains the main stay of therapy of overt HE, despite the paucity and inconsistency of clinical trials demonstrating its efficacy (11). The dosage should be adjusted to accomplish two to three soft bowel movements each day. Lactulose can be given through a nasogastric tube or through retention enemas. The usual dose is 30-120 ml each day in divided doses. Stool pH should be below six. Side effects include bloating and flatulence. Severe diarrhea with dehydration and hyperglycemia and acidosis occurs if the dosage is too high.

Non absorbable antibiotics neomycin, metronidazole, and paromomycin are traditional antibiotics for the treatment of HE (12). Due to ototoxic and nephrotoxic side effects, neomycin is now used infrequently. Metronidazole does not cause much side effects but therapy should not extend beyond two weeks to avoid neuropathy. More recently rifaximin has demonstrated to be as good as lactulose (13) or lactitol (14, 15) for patients with hepatic encephalopathy.

2. Increase ammonia detoxification:

Levels of ammonia can be decreased by detoxification. L-ornithine- L-aspartate (LOLA), the salt of the natural amino acids ornithine and aspartate acts through the mechanism of substrate activation to detoxify ammonia. Detailed mechanism of action and clinical trials on LOLA are discussed below.

L-ornithine- L-aspartate (LOLA):

L-ornithine- L-aspartate (LOLA) is the salt of the natural amino acids ornithine and aspartate.

1. Mechanism of action:

LOLA stimulates the urea cycle (which metabolizes ammonia to urea) in the liver (16,17). In the periportal hepatocytes that synthesize urea, ornithine serves as an activator of ornithine transcarbamoylase and carbamoyl phosphate synthetase. In addition, ornithine can acts as a substrate for urea genesis. Hence, LOLA can activate the periportal urea cycle in the liver. Aspartate and ornithine, after conversion to alpha- ketoglutarate, also serves as carbon sources for perivenous glutamine synthesis. In the skeletal muscle, LOLA upregulates glutamine synthesis by substrate provision for glutamine synthetase, although decreased muscle mass in cirrhosis does not allow this synthesis to be significant. Ammonia is consumed during urea formation and glutamine synthesis, and thereby LOLA decreases blood ammonia levels. Urea and glutamine (after further metabolism) can be excreted via the kidneys. LOLA thus activates the two important metabolic pathways in the human body for the detoxification of ammonia. In cirrhosis, there is some remaining liver cell mass that retains capacity to detoxify ammonia as opposed to acute liver failure.

2. Trials of LOLA in Hepatic encephalopathy:

LOLA has been used for many years for the treatment of HE in cirrhosis of the liver, especially minimal and overt chronic low grade HE. The clinical efficacy of LOLA has already been comprehensively investigated and reported in therapeutic observations, clinical trials (16, 18-25) and meta-analysis (26,27). In these studies, the use of LOLA as infusion, oral administration or a combination of the two, was documented in patients with mild to severe liver insufficiency. LOLA showed a statistically significant effect with respect to an improvement in mental state (reduction in the HE grade), increased detoxification (reduction of the ammonia concentration in the blood) and positive effects on psychomotor function (reduction of time required in the number connection test) in Minimal Hepatic Encephalopathy and overt chronic Grade I-II Hepatic Encephalopathy, and acute overt HE. With these findings, evidence-based medicine criteria for demonstrating efficacy have been fulfilled.

In a recent randomized placebo controlled study conducted at Karachi (25), patients with acute HE were randomized to receive LOLA or placebo. NCT-A, ammonia level, clinical grade of HE and duration of hospitalization were assessed. Improvement in HE was higher (n=40, 66.7%) in LOLA group (n=28, 46.7%, p=0.027). Duration of hospitalization was lower in LOLA group compared to placebo (p=0.025). No side effects were observed in either group.

3. Adverse effects of LOLA L-ornithine- L-aspartate is usually well tolerated (18-25). No serious adverse events have been reported so far in clinical trials. The various adverse events reported in about 14% patients treated with LOLA include:

1. Nausea

2. Vomiting

3. Fatigue

B. Materials and Methods

1. Study design and setting:

This will be a prospective, randomized, double blind, placebo controlled interventional study.

The study will be conducted on patients of cirrhosis admitted with overt HE in the Department of Gastroenterology, Dayanand Medical College and Hospital, Ludhiana and Department of Hepatology, GB Pant Hospital, New Delhi. Informed consent shall be taken from the nearest relative of the patient for enrollment in the trial.

The study shall be presented for approval to the Institutional Ethics Committee prior to the enrollment of patients into the study. It shall be registered with Clinical Trial Registry, India and the ClinicalTrials.gov registry.

2. Study population:

Inclusion and exclusion criteria have been mentioned elsewhere.

3. Study Methods:

Assignment: Consecutive patients diagnosed to have acute overt HE will be randomized into two groups (group A and B) using sealed opaque envelopes containing computer-generated random numbers. There shall be no restriction, blocking or stratification of the randomization sequence. The research coordinator who will generate the sequence shall have no role in recruitment, treatment, or assessment of patients.

Masking: Sequentially numbered boxes containing identical LOLA or placebo ampoules, according to the allocation sequence will ensure allocation concealment. The numbering of the boxes will be done by research coordinator, and concealed from the treating consultants. All study personnel will be blinded to the treatment assignment (placebo or LOLA) for the duration of the study. Placebo and LOLA will be similar in appearance and in the mode of administration. The code of the allocation sequence will remain with the research coordinator. It will be revealed only after the recruitment, data collection and analysis of results has been carried out. The coordinator will not have any access to the patients involved in the study.

Randomization implementation: Enrollment of patients, assessing eligibility and obtaining informed consent will be carried out by one of the investigators (S.S. Sidhu or O. Goyal, BC Sharma) Study Intervention: The patients will be randomized to receive either placebo or LOLA at dose of 30 grams daily, by intravenous infusion over 24 hours. (The study drugs and placebo will be provided by Win Medicare Pvt Ltd., 1400, Modi tower, 98, Nehru Place, New Delhi- 110019). LOLA will be supplied as ampoules (each ampoule containing 5 grams LOLA in 10 ml clear solution). Six ampoules (i.e 30 g of LOLA) will be infused over 24 hours. The placebo vials (10 ml sterile water in each vial) will be identically supplied and infused. The dose of LOLA (30 g in 24 hours) was based on previous studies, showing the efficacy of this dose in decreasing ammonia levels (17,26,28). Both groups shall receive treatment for 5 days. Patients in both the groups who continue to have hepatic encephalopathy at the end of study period (5 days), will receive standard of care treatment, and would be counseled about liver transplant.

4. Laboratory tests:

Biochemical tests: Hemogram, blood glucose, liver function tests, prothrombin time, serum electrolytes, blood urea and serum creatinine will be done at baseline, and at 2nd and 5th day of treatment, or earlier if indicated. Serum AFP will be done at admission. Serum cytokine levels (Interleukin 1, 6, 10 and TNF-alpha) levels will be done at baseline and after 5 days of treatment.

Microbiologic tests: A diagnostic paracentesis will be done in all patients with ascites, at baseline, to diagnose Spontaneous Bacterial Peritonitis. A repeat cell count (Total and differential) shall be done on day 5 with patients diagnosed to have Spontaneous Bacterial Peritonitis. Blood culture, urine culture, cultures of aspirates from endotracheal tubes in ventilated patients for aerobic and anerobic bacteria, and fungi shall be done. A chest radiograph shall also be done.

Ammonia estimation: Fasting venous ammonia levels will be estimated by using the blood ammonia meter (PocketChem BA) at baseline and then daily for the next 5 days. The PocketChem BA ammonia meter is an apparatus for quick bedside blood ammonia estimation. It has been shown to have acceptable precision, adequate linearity, and satisfactory agreement with a enzymatic reference method commonly used in clinical laboratories (29).

Measurement Principle: The PocketChem BA measures blood ammonia based on the micro-diffusion method. When the blood sample (20 microlitre) is applied to the sample-receiving layer of the test area on the test strip, the alkaline buffer agent (borate buffer) impregnated in the layer dissolves making the specimen alkaline. The ammonium ions in the specimen are gasified by the alkaline state into ammonia gas. The ammonia gas passes through the pores of the spacer to the indicator (bromocresol green) triggering color development. As the degree of color development is proportional to the concentration of ammonia gas produced, the blood ammonia level is quantitatively determined by measuring the color.

Tests for etiologic evaluation: Etiology of cirrhosis will be taken as alcohol if there is a history of significant alcohol intake (40-60gm/day for females, and 60-80 gm/day for males for 10 years). Each patient will be tested for Hepatitis B surface antigen (HbsAg) and Anti-hepatitis C (HCV) antibody using a third generation commercial ELISA. Wherever indicated, autoimmune hepatitis will be diagnosed using antinuclear antibody, anti-smooth muscle antibody and anti-LKM; and hemochromatosis using serum iron, TIBC, ferritin and transferrin saturation. Each patient shall have an abdominal ultrasonography. UGI endoscopy would be done, if indicated.

5. Standard of Care Treatment:

Standard of care treatment for patients with cirrhosis and overt acute encephalopathy shall be given to all patients.

1. Identification of other potential causes for altered mental state i.e. head injury or drug intoxication shall be done.

2. Identification and treatment of the precipitating causes of encephalopathy such as sepsis, gastrointestinal bleeding, hypokalemia (serum Potassium < 3.5mEq/L), alkalosis, azotemia, dehydration, diuretics, constipation, large protein intake and psychoactive drugs shall be done.

3. Lactulose syrup: 30-120 ml in three divided doses through a nasogastric tube/ orally to produce 2-3 semi formed stools and/or lactulose retention enemas (300 ml lactulose +700 ml water) twice daily. No other ammonia lowering agent shall be given to these patients.

6. Monitoring and follow-up:

Clinical Monitoring:

All patients will be admitted to the intensive care unit/ high dependency unit, and shifted to ward once they revert back to grade I HE. Continuous monitoring of vital signs shall be done. Neurologic monitoring shall be done twice daily and grading of mental state will be as per the West Haven Criteria.

Definition of Response to therapy:

The assessment of the clinical response will be defined as follows:

1. Resolution: disappearance of the HE clinical syndrome during the study

2. Improvement: a decrease in the HE by 1 grade, but not reaching grade 0

3. No Improvement: no improvement in HE

4. Failure: shift to a higher grade of HE.

Biochemical monitoring:

Biochemical monitoring and monitoring of ammonia levels shall be done as mentioned above (under 'laboratory tests')

Monitoring for Adverse Events:

Any adverse event will be recorded specifying the time of onset, the duration, the severity and the relationship to the test medication.

Tolerability: Tolerability of the study drug will be assessed by comparison of full blood cell count, liver function tests and renal function tests at baseline and at end of treatment.

7. End points:

Primary end-point

1. Completion of 5 days of treatment

Secondary end-point

1. Liver related death

2. Death due to other causes

3. Discontinuation due to adverse effects

4. Discharge from hospital

8. Sample size: Sample size for this study was estimated using results of a previous study which reported complete recovery of encephalopathy in 79% patients in LOLA group and 55.6% patients in the placebo group (25). At 80% power and a 5% significance level (two-sided), 71 patients in each group would be required to detect a 22% difference in proportions. Assuming a dropout rate of 15% approximately (28), we will need to enroll 164 patients, i.e. 82 in each treatment arm.

9. Statistical Analysis: A chi-squared test will be used to compare the proportion of patients with complete reversal of HE after 5 days in LOLA treatment and placebo groups. A 95% confidence interval for the difference in proportions will also be calculated. A Chi-squared test will then be used to compare the HE grading at 5 days between the groups. Blood ammonia levels will be compared between groups using an independent samples t-test; while length of hospital stay is not expected to be normally distributed and therefore will be compared using a non-parametric Mann-Whitney test. All statistical tests will be 2-sided and using a 5% significance level.