Phenylketonuria (PKU) Study Notes

• Study notes for Peds Exam 4 (Part 1)

Phenylketonuria (PKU)

• PKU is an inherited metabolic disorder where newborns lack phenylalanine hydroxylase.
• This deficiency leads to the accumulation of phenylalanine in the body.
• PKU follows an autosomal recessive inheritance pattern.
• PKU can cause cognitive impairment and developmental delays.
• Other signs include growth failure and a musty odor in the urine.

Newborn Screening for PKU

• All newborns undergo blood spot analysis within 2 days of birth for early detection.
• Ideally, the blood draw occurs 48-72 hours after birth, but no sooner than 24 hours after the start of nutrition.
• The expected range of phenylalanine is 0.5-1 mg/dL.
• A Guthrie test confirms the diagnosis when the blood spot analysis indicates high phenylalanine levels.

Maternal Considerations for PKU

• Mothers with PKU must follow strict dietary guidelines starting 3 months before conception and throughout pregnancy.

Dietary Management of PKU

• Dietary restrictions should be initiated ASAP, ideally within 7-10 days of birth
• Newborns should receive a formula that is low in phenylalanine, with an intake of 20-30 mg phenylalanine/kg/day.
• Breastfeeding is allowed in moderation due to the presence of phenylalanine in breast milk.
• Limit foods high in phenylalanine, such as meat, eggs, and milk.
• Encourage consumption of foods low in phenylalanine like potatoes, lettuce, peas, and bananas.

Nursing Care for PKU

• Provide parents with support and education about managing PKU.
• Consult with a registered dietitian for dietary guidance.
• Provide referrals to PKU support groups.
• Sapropterin is a medication that can help decrease phenylalanine levels.

Diabetic Ketoacidosis (DKA)

• DKA occurs when the body uses fat for energy due to insufficient insulin, leading to the production of ketones and excess acid in the blood.
• A glucose level greater than 330 mg/dL is indicative of DKA.

DKA Manifestations

• Fruity acetone breath
• Kussmaul's respirations
• Confusion

DKA Treatment Priorities

• Treat DKA ASAP
• Address dehydration with rapid infusion of isotonic saline.
• Monitor and treat hyperkalemia with a regular insulin drip.
• When blood glucose levels approach 250 mg/dL, add glucose to IV fluids to maintain levels between 120-240 mg/dL.
• Check glucose levels every 15-20 minutes until glucose is down to 120-150 mg/dL.

Potassium Management in DKA

• Initially, potassium levels may be elevated, but they can drop as dehydration is corrected.
• Monitor for hypokalemia as treatment progresses.
• If potassium levels remain elevated, add potassium to the IV fluids.
• Ensure the child voids before adding potassium to IV fluids.

DKA Labs

• Blood glucose level
• Ketone level in urine
• BUN
• Electrolytes
• ABG
• CBC

Hyperglycemia

• Hyperglycemia is defined as blood glucose levels usually greater than 250 mg/dL.
• Key symptoms include thirst, polyuria (early), and oliguria (late).
• Rapid, deep respirations with acetone/fruity odor are characteristic (Kussmaul respirations).
• Other symptoms: nausea, vomiting, abdominal pain, warm/dry/flushed skin with poor turgor, dry mucous membranes, confusion, weakness, lethargy, weak pulse, and diminished reflexes.

Hypoglycemia

• Hypoglycemia is defined as blood glucose less than 60 mg/dL.
• Key symptoms include hunger, lightheadedness, shakiness, diaphoresis, headache, and blurred vision.
• Other symptoms: anxiety, irritability, pallor, cool skin, normal or shallow respirations, tachycardia, palpitations, strange feelings, decreased level of consciousness, difficulty thinking, behavior changes, slurred speech, and potential seizures/coma.

Blood Glucose Monitoring

• Assess blood glucose levels before every meal and at bedtime.

Hyperglycemia Nursing Care

• Encourage oral fluid intake.
• Administer insulin as prescribed.
• Test urine for ketones and report if levels remain high.
• Consult the provider if symptoms persist or worsen.

Hypoglycemia Nursing Care

• Check glucose levels first.
• Follow guidelines from the provider or diabetes educator.
• Treat with 10-15 g of simple carbs (e.g., 1 tbsp sugar, 4 oz juice, 8 oz milk, 2-3 glucose tablets, 4 oz soft drink).
• Use milk or fruit juice for mild reactions.
• Monitor blood glucose frequently and recheck after 15 minutes post-treatment.
• After treating with simple carbs, follow with complex carbs (whole grains, legumes, fruits, nuts, starchy veggies).
• For unconscious patients or those unable to swallow, administer glucagon SC or IM and notify the provider.
• Administer simple carbs as soon as tolerated after glucagon administration.
• Watch for vomiting after glucagon administration and take precautions against aspiration.

Normal Glucose Lab Values

• Normal 8-hour fasting glucose: under 100 mg/dL
• Normal random glucose: under 140 mg/dL
• Normal oral glucose tolerance test: under 140 mg/dL after 2 hours
• Normal HbA1c: 4-6%

Abnormal Glucose Lab Values

• Abnormal 8-hour fasting glucose: 120 mg/dL or higher
• Abnormal random glucose: 200 mg/dL or higher
• Abnormal glucose tolerance test: 200 mg/dL or higher
• Abnormal HbA1c: greater than 6.5%

Prediabetes Indication

• Glucose lab values falling between normal and abnormal ranges may indicate prediabetes.