Hyperammonaemia Reduces Restorative Sleep for Patients with Cirrhosis
Italian and Swiss researchers confirm that induced hyperammonaemia
significantly increases daytime sleepiness in patients with cirrhosis.
The findings available in the March issue of Hepatology,
a journal published by Wiley-Blackwell on behalf of the American
Association for the Study of Liver Diseases, show that higher blood
levels of ammonia reduced the ability of cirrhotic patients to produce
restorative sleep.
Chronic liver disease can lead to cirrhosis—a condition where scar
tissue replaces healthy tissue, resulting in decreased blood flow
through the liver and reduced liver function. Viral hepatitis, heavy
alcohol use and obesity are among the causes of cirrhosis according to
the National Institute of Diabetes and Digestive and Kidney Diseases
(NIDDK).
In patients with chronic liver failure neuropsychiatric abnormalities
may arise—termed hepatic encephalopathy (HE)—which experts believe to be
due to neurotoxic substances that originate in the gut and are not
cleared by the liver, such as ammonia. HE is common following a
gastrointestinal bleed, which can be simulated by the oral
administration of a mixture of protein mimicking that contained in blood
(‘amino acid challenge’; AAC).
To investigate the effects of excess ammonia and HE on sleep-wake
patterns in patients with cirrhosis, Dr. Sara Montagnese and colleagues
from the Dipartimento di Medicina in Padova, Italy and the Institute of
Pharmacology and Toxicology in Zurich, Switzerland, induced
hyperammonaemia in participants by an AAC. Ten cirrhotic patients and
ten healthy controls underwent eight days of sleep quality monitoring,
neuropsychiatric/wake and sleep EEG assessment prior to and following
the AAC, and hourly ammonia and sleepiness assessments for eight hours
post-AAC.
“Our study found that induced hyperammonaemia led to a significant
increase in daytime sleepiness in both patients and healthy volunteers,”
said Dr. Montagnese. The authors also report changes to the EEG
architecture of a sleep episode (nap) in patients with cirrhosis, which
they believe points to a reduced ability to produce restorative sleep.
Dr. Montagnese concludes, "Our findings have important clinical
implications in that subjective sleepiness may be used as a surrogate
marker for HE." The authors also suggest that strategies aimed at
reducing daytime sleepiness may result in improved sleep at night.
