Page 839 - Problem-Based Feline Medicine

37 – THE CAT WITH STUPOR OR COMA 831

Hepatic encephalopathy in older animals can be associ- ● Weakness and seizures are most common. Affected
ated with liver failure such as with cirrhosis. animals may be depressed, and have intermittent
twitches or tremors.
Hypoglycemia can occur secondary to some endocrine
disorders such as hypoadrenocorticism and insulinoma Clinical signs of hypernatremia include adipsia, depres-
or from lack of production by the liver in young kittens sion, seizures progressing to stupor and coma.
or in cats with liver failure, and some tumors. However,
Uremic encephalopathy may result in depression, stu-
it is most common following overdose of insulin in
por, myoclonic movements, generalized weakness and
diabetic cats.
partial or generalized seizures.
Because the central nervous system (CNS) requires
a constant supply of glucose, clinical signs of hypo-
Diagnosis
glycemia relate to CNS dysfunction and activation of
the sympathetic nervous system and include depres- Diagnosis of metabolic encehalopathy is suggested by
sion, seizures and tremors. metabolic abnormalities on routine physical examina-
tion or laboratory evaluations (CBC, serum biochemi-
Cats with diabetic ketoacidosis may have cerebral
cal analysis, urinalysis).
signs (depression), but whether these changes relate to
the hyperglycemia or other physiologic derangements Diagnosis of hepatic encephalopathy is supported by
such as hyperosmolality is unknown. abnormal liver function studies such as elevated pre-
or post-prandial bile acids or elevated fasting ammo-
Hypernatremia can result in abnormal mentation pro-
nia. Ammonia chloride challenge is rarely required in
gressing to stupor and coma.
cats to make a diagnosis.
● Hypernatremia usually results from inadequate
● Abdominal ultrasound may show abnormal liver
drinking. This may occur due to alterations in
vasculature.
awareness of thirst or inability to physically move
● Portal vein angiography or direct visualization at
to water.
surgery may be needed for accurate diagnosis.
● Idiopathic adipsia can occur, usually in younger
cats. Diagnosis of hypoglycemia is based upon finding
hypoglycemia (blood glucose < 3.3 mmol/l: 60 mg/dl)
Hypernatremia and adipsia in an older animal should
in the face of clinical signs.
warrant an evaluation for structural intracranial disease
● Concurrent measurement of serum insulin concen-
such as hydrocephalus and brain tumor.
tration will help identify an insulin-secreting
Renal failure and pancreatitis may affect cerebral func- tumor, by demonstrating inappropriately high
tion if severe, producing depression, stupor, tetany or insulin concentration in the presence of hypoglycemia.
seizures. Non-beta cell tumors producing hypoglycemia have
low to undetectable insulin concentration during
hypoglycemia.
● Insulin-treated diabetic cats with clinical hypo-
Clinical signs
glycemia need re-evaluation. Some cats will be in
Neurologic signs often include seizure, alterations in diabetic remission and do not need insulin. Other
mentation, behavior abnormalities and paresis. cats have accidentally received a higher than nor-
mal dose. This may occur when insulin syringes are
Neurologic signs are often symmetrical and may be
changed from U100 to U40 or from 0.5 ml to 1 ml
episodic.
syringes. Accidental overdose may also occur when
Clinical signs of hepatic encephalopathy include someone other than the owner gives the insulin.
seizures, ptyalism and mentation changes. Careful history taking will identify these problems.
In hypoglycemia, clinical signs occur due to decreased Diagnosis of hypernatremia is based upon finding
CNS glucose supply (neuroglycopenic signs) or elevated serum sodium (> 165 mmol/l: 165 mEq/l) in
because of sympathetic nervous system activity. the face of clinical signs.