59: Hyperglycemia

I. PROBLEM

The nurse reports an infant has a blood glucose level of 240 mg/dL. The incidence of hyperglycemia is higher in preterm than term infants (60–80% in extremely low birthweight [ELBW] infants). The definition and treatment of hyperglycemia is controversial. Following are some of the definitions used:

1. Whole blood glucose >120–125 mg/dL or a plasma glucose >145–150 mg/dL regardless of gestational or postnatal age or weight

2. Whole blood glucose >125 mg/dL in term and >150 mg/dL in preterm

3. Whole blood glucose >215 mg/dL (operational definition per Edmund Hey)

II. IMMEDIATE QUESTIONS

1. What is the serum glucose value on laboratory testing? Bedside glucose testing using reagent strips is widely used for screening. It is best to confirm a serum glucose level from the laboratory before initiating treatment. Whole blood glucose measurements are 10–15% lower than plasma glucose.

2. Is glucose being spilled in the urine (glucosuria/glycosuria)? Glucosuria (glycosuria) is not reliable for hyperglycemia since it can occur at normal glucose blood levels. Mild hyperglycemia can also be associated with mild or no glucosuria. A trace amount of glucose in the urine is accepted as normal. If the urinary glucose level is +1, +2, or greater, the renal threshold has been reached with an increased chance of osmotic diuresis. Some institutions accept a urinary glucose level of +1 without treating the patient (controversial). Some authors suggest that the presence of >1+ glucosuria suggests osmolar changes and should be treated. Note: Each 18-mg/dL rise in blood glucose causes an increase in serum osmolarity of 1 mOsm/L.

3. How much glucose is the patient receiving? High glucose intake is a common cause of hyperglycemia in a preterm infant. Levels >10–12 mg/kg/min may result in hyperglycemia, and hyperglycemia may occur at lower levels if the infant is stressed. Normal initial maintenance glucose therapy in infants not being fed orally is 6–7 mg/kg/min on day 1 to 8–9 mg/kg/min on days 2 to 7. ELBW infants should be started at 4–6 mg/kg/min (see Chapter 12).

4. Are there signs of stress? Stressful situations like surgery may cause hyperglycemia by inducing a stress response (catecholamine mediated).

5. Does the infant have necrotizing enterocolitis (NEC) or sepsis? When an infant who has had normal glucose levels develops hyperglycemia and there is no change in IV fluids, or if an infant who is being fed only enterally suddenly develops hyperglycemia, suspect either sepsis or NEC. Hyperglycemia is seen more frequently in fungal infections than in bacterial infections. In Candida sepsis, infants may have a high blood sugar for 2–3 days before any other clinical signs appear.

6. What is the birthweight of the infant? Low birthweight is the most significant risk factor for hyperglycemia at any gestational age. The incidence is ∽2% in infants >2000 g, 45% in infants <1000 g, and 80% in infants <750 g.

7. Does the infant have any of the high-risk factors for hyperglycemia? Risk factors include gestational ...