In the author's opinion routine
laboratory screening of geriatric dogs with heart disease is mandatory, particularly
before the administration of drugs which might be hepatotoxic or nephrotoxic such
as the cardiac glycosides.
Chronic diuretic use may induce hypokalaemia, indeed hypokalaemia is probably common
but rarely detected because it is not routinely screened for. Elevated liver enzymes
are likely to be detected if hepatic congestion is present, and prerenal azotaemia
is common in the presence of reduced cardiac output.