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Nocturnal hypoglycemia
would correctly be defined as
hypoglycemia
occurring at night, but commonly is
defined as hypoglycemia
while asleep.
It is common in patients with
type 1 diabetes
and is usually asymptomatic.
Nocturnal hyperinsulinemia frequently occurs with insulin therapy, and although blood
glucose levels are often low during sleep,
they are seldom measured routinely. Almost 50% of all episodes
of severe hypoglycemia occur at night during sleep.
Such episodes can cause convulsions and coma and have
been implicated as a precipitating factor in cardiac arrhythmias resulting
in sudden death —
the "dead-in-bed syndrome."
On the day after an episode of nocturnal hypoglycemia,
mood and well-being may be
affected. Recurrent exposure to nocturnal
hypoglycemia may impair cognitive function, and is thought to perhaps
lead to the development of
"hypoglycemia unawareness."
Prevention
Various strategies can be used to
minimize the nocturnal hyperinsulinemia that is
associated with many
insulin replacement regimens.
Switching the patient from older programs (such as NPH at suppertime), and avoidance of
boluses of short-acting insulin at bedtime, are particularly important to consider.
Regular
blood glucose monitoring (particularly at bedtime), the
ingestion of appropriate bedtime snacks, and the utilization
of short- and long-acting insulin analogues may
all help to prevent or minimize the frequency of nocturnal hypoglycemia.
In one study,
Most hypoglycemic episodes (10 of 14, 71%) occurred with no snack compared to any snack. Eating a snack
at bedtime is especially important if there was
heavy exercise late in the day or evening — exercise
can result in delayed hypoglycemic events.
Diagnosis
If a patient has nocturnal hypoglycemia, he/she may either
awaken at the time of the event, and realize that they are low,
or may awaken later with a severe headache.
The
diagnosis
can readily be made by the patient's bed partner: the patient
might be asleep, but sweating profusely, and thrashing about.
Routine checking of blood sugar levels at 3 AM may detect
unsuspected nocturnal hypoglycemia.
Use
of continuous glucose monitoring systems
may also provide important information.
If the patient sleeps through the episode, then checks a blood sugar
level at dawn the following morning, it may be high
from "rebound"
(also called
the
Somogyi effect).
Also see
high at dawn
Nocturnal hypoglycemia: clinical manifestations and therapeutic strategies toward prevention.
Endocr Pract. 2003 Nov-Dec;9(6):530-43.
Abstract at
PubMed.
Nocturnal hypoglycemia detected with the Continuous Glucose Monitoring System in pediatric patients with type 1 diabetes.
J Pediatr. 2002 Nov;141(5):625-30.
Abstract at
PubMed.
Impact of bedtime snack composition on prevention of nocturnal hypoglycemia in adults with type 1 diabetes undergoing intensive insulin management using lispro insulin before meals: a randomized, placebo-controlled, crossover trial.
Diabetes Care. 2003 Jan;26(1):9-15.
Abstract at
PubMed.
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