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ABC of Diabetes
by Peter J. Watkins
Diabetic ketoacidosis and management
of diabetes during surgery
Ketoacidosis
Ketoacidosis results from a lack of insulin. In practice it
is
usually due to:
* stopping insulin or reducing the dose either in error or
deliberately
* resistance to insulin during infections or other
intercurrent illness
* the unrecognised onset of Type 1 diabetes.
The clinical onset of ketoacidosis occurs over hours or
days. Symptoms of uncontrolled diabetes are always present.
Vomiting in Type 1 diabetic patients is always serious.
Patients usually consult their doctors during the preceding
days, but the presence of uncontrolled diabetes is
frequently overlooked. Diabetic control should always be
assessed if a diabetic patient becomes unwell for any
reason. Many cases of ketoacidosis could be prevented.
Preventing ketoacidosis:
sick day rules
During any illness or infection the blood glucose
concentration tends to increase and diabetic control
deteriorates. Most patients then need a larger dose of
insulin than usual, and some who normally take tablets may
need insulin just during the illness. The increased need for
insulin occurs even when the appetite declines or vomiting
begins.
Every insulin treated patient should understand that insulin
should never be stopped. Stopping or even reducing insulin
during the course of an illness often leads to diabetic
ketoacidosis.
When a diabetic person is ill
the normal insulin dose should be continued, carbohydrate
taken in some palatable fluid form, and the blood tested
regularly—four times a day if necessary. If blood glucose
readings greater than 15 mmol/l are obtained the dose of
insulin should be increased. Additional doses of insulin
(about 8 units) may also be given at noon or bedtime when
control is very poor. It is preferable to make these
adjustments with short acting (soluble) insulin if this is
available. If vomiting continues without remission for more
than a few hours, admission to hospital for treatment with
intravenous fluids and insulin is advisable to prevent
ketoacidosis.
Assessment of blood or urine ketones during illness is
helpful. Using the new blood ketone meters, readings of
1·0-3·0 mmol/l taken in conjunction with the blood glucose
reading usually indicate the need for additional insulin;
readings should be repeated within two to four hours. If
they persist or increase above 3·0 mmol/l, specialist advice
is required from the hospital clinic staff. Ketonuria can be
detected using Ketostix, which are readily available.
Recognising ketoacidosis
Dehydration is the most obvious clinical feature of patients
with ketoacidosis. They are also drowsy, but rarely
unconscious - “diabetic coma” is an inappropriate
description; they are often overbreathing, but not usually
breathless; their breath smells of acetone (though many
people cannot smell this); and many also have the gastric
splash. In more severe cases patients are hypothermic (even
in the presence of infection) and hypotensive. Hyperosmolar
non-ketotic (HONK) patients are usually grossly dehydrated
but without overbreathing or the smell of acetone.
Inexperienced clinicians often have difficulty in
recognising patients with this condition, especially when
they seem deceptively well.
Diagnosis
The diagnosis of ketoacidosis is confirmed by laboratory
tests.
* Blood glucose concentrations may range from slightly
increased to extreme hyperglycaemia. The blood glucose
concentration itself does not usually indicate the severity
of the illness, although most patients are seriously unwell
when it is greater than 30 mmol/l.
* Blood acid-base status pH ranges from 6·9 to normal. The
bicarbonate level is depressed.
* Plasma ketones are easily detectable with a ketone meter
and exceed 3·0 mmol/l.
* Urine test shows heavy glycosuria and ketonuria.
* Electrolytes: the serum potassium concentration is either
normal or raised, and very rarely low. This measurement is
vital, and life-saving treatment is needed to maintain
potassium values in the normal range. The sodium
concentration is normal or reduced, and urea and creatinine
concentrations are often raised through dehydration.
* Blood count: if a blood count is performed the white cell
count is often spuriously raised to 15-20
109/l even in the absence of infection.
Serum amylase is sometimes
moderately elevated in patients with diabetic ketoacidosis:
it is of salivary origin and need not be indicative of
pancreatitis
Note: The rest of the chapter
is omitted.
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