- Outline the current recommendations for diabetes mellitus screening.
Universal screening is not generally recommended. Screening is more accepted, but not
universal, in patients who are obese, people over 45 years of age, people with a family history
of diabetes, and members of certain minority groups (blacks, Hispanics, Pima Indians).
Screening in pregnancy is mandatory! - Define diabetes.
Diabetes is defined as (1) a glucose level greater than or equal to 126 mg/dL after an overnight
(or 8-hour) fast on two separate occasions or (2) a random glucose level greater than
200 mg/dL or (3) an A1C level of greater than 6.5 percent on two separate occasions. If the
patient has classic symptoms of diabetes (see hereafter), one test is sufficient to make the
diagnosis. In an asymptomatic patient, it is best to repeat the test. An oral glucose tolerance
test is common in pregnancy; otherwise, it is rarely used because of poor reproducibility and
patient compliance. With a glucose tolerance test, diabetes is diagnosed when glucose levels in
the blood reach or exceed 200 mg/dL within 2 hours of receiving a 75 g oral dose of glucose. - What are the goals of treatment in terms of glucose levels?
The goals are to keep postprandial glucose levels less than 180 mg/dL and fasting glucose
levels 70–130 mg/dL. Attempts at stricter control may result in hypoglycemia; watch for
symptoms of sympathetic nervous system activation and mental status changes. - What is a good measure of long-term diabetes control?
Hemoglobin A1c measures the “average” control of blood glucose level over the prior 2 to
3 months. The current recommendation is to keep the hemoglobin A1c level below 7. This is a
good way to catch patients with nocturnal hyperglycemia or less-than-honest patients who
falsely record low glucose test readings. A rough rule of thumb is that hemoglobin A1c times
20 equals the average blood glucose level. - When a nondiabetic patient presents with hypoglycemia, how can you
distinguish between factitious disorder (exogenous insulin) and an insulinoma
(endogenous insulin)?
Measure the C-peptide level. C-peptide is produced whenever the body makes insulin, but it is
absent in prescription insulin preparations. Therefore, C-peptide is high with an insulinoma
and low with factitious disorder. This is a classic USMLE question. - What should you remember before giving intravenous iodinated contrast
material to a diabetic patient or a patient with renal insufficiency?
Diabetic patients and patients with renal insufficiency are prone to acute renal failure from the
intravenously administered iodinated contrast agents used for intravenous pyelography (IVP),
conventional angiography, and computed tomography (CT). You need to weigh carefully the
risk-to-benefit ratio of using intravenous contrast agents. If you choose to give contrast, first
hydrate the patient well with intravenous fluids to avoid renal shutdown. Acetylcysteine and
bicarbonate may decrease the risk of contrast nephropathy in patients at high risk. The
concerns about intravenous iodinated contrast do not apply to oral contrast agents (e.g.,
barium). - What is diabetic ketoacidosis (DKA)? How is it treated?
All type I diabetics will die without insulin. DKA is what happens before they die. Clinically, look
for Kussmaul breathing (deep, rapid respirations), dehydration, hyperglycemia, acidosis
(due to excessive ketone formation), and increased ketones in the serum (often associated
with a fruity odor of the breath) and urine.
Treatment involves intravenous fluids, insulin, and replacement of electrolytes (especially
potassium and phosphate). For the boards, do not use bicarbonate to correct acidosis.
Remember to search for the cause of DKA, which most commonly is noncompliance with
insulin therapy. The second most common cause is an infection. The mortality rate of DKA
with current treatment efforts is less than 10%. - What is nonketotic hyperglycemic hyperosmolar state? How is it treated?
It is what happens to type II diabetics who go without adequate treatment before they die.
Hyperglycemia and increased serum osmolarity are present in the absence of ketones and
acidosis. Most patients are severely dehydrated; the first three treatments are thus “fluids,
fluids, and fluids” (i.e. intravenous hydration with normal saline). Insulin and electrolyte
replacement also is required. The mortality rate can approach 50% if mental status changes
are present at the time of diagnosis. - What are the classic presenting symptoms of new-onset diabetes?
Polyuria, polydipsia, and polyphagia (pee a lot, drink a lot, and eat a lot). You also should be
suspicious if patients present with candidal infections (e.g., thrush or vaginal yeast infection),
64 CHAPTER 7 DIABETES MELLITUS
lose weight (as a result of excessive urination), or have blurry vision. Prolonged hyperglycemia
causes the lenses in the eyes to swell, and the patient may become myopic. Older patients may
even claim that they no longer need their reading glasses (i.e., presbyopia is temporarily
corrected by lens swelling).