Nutritional management of chronic disease — formative SAQs

SAQ 1 — The cardiac infant with failure to thrive (20 marks, ~15 minutes)

A four-month-old infant with a large ventricular septal defect and pulmonary hypertension is reviewed in clinic. He is tachypnoeic, sweats with feeds, takes small volumes and tires quickly, and his weight has fallen from the twenty-fifth to below the third centile over eight weeks while his length has tracked along the tenth. He is on a standard infant formula at around one hundred kilocalories per kilogram per day. ^[9]

Questions

1. Give the dominant mechanism of his malnutrition and the two bedside features that support it. (5 marks) ^[9]
2. Outline the anthropometric assessment of his malnutrition using the Academy of Nutrition and Dietetics and ASPEN framework. (5 marks) ^[1]
3. Outline the nutrition management, including the energy target, the feed strategy and the feeding route. (5 marks) ^[9]
4. Explain why simply increasing the volume of standard formula may fail and worsen his cardiac state. (3 marks) ^[9]
5. Give two complications of untreated malnutrition in this infant and why nutrition is an outcome of his care. (2 marks) ^[9]

Model answer (must-hit)

1. The dominant mechanism is increased metabolic demand from the large left-to-right shunt and the work of the over-circulated heart, compounded by decreased intake from tachypnoea and fatigue on feeding. The bedside features are the sweating with feeds and the rapid tiring that limits the volume taken, and the weight that has fallen across centile lines while the length has held, showing the energy deficit is acute and driven by demand. ^[9]
2. The anthropometric assessment plots the weight, length and body mass index on the appropriate chart and converts them to z-scores, and measures the mid-upper arm circumference as a muscle and fat marker. The Academy of Nutrition and Dietetics and ASPEN consensus diagnoses malnutrition when two or more of six indicators are abnormal, each graded mild, moderate or severe: the weight-for-length z-score, the body mass index for age z-score, the length for age z-score, the mid-upper arm circumference z-score, the rate of weight gain and the rate of length gain. His falling weight-for-length and mid-upper arm circumference, with a normal length, would grade him as acute moderate or severe malnutrition. ^[1]
3. The energy target is around one hundred and thirty to one hundred and fifty kilocalories per kilogram per day, achieved by fortifying the formula to a higher calorie density rather than by increasing the volume, because volume loading worsens the heart failure. The strategy is concentrated or supplemented feeds with added carbohydrate and fat modules, given more frequently in smaller volumes that the tiring infant can manage. A nasogastric tube is used early for bolus or continuous feeds when oral intake cannot meet the target, and a gastrostomy is considered for the longer-term cardiac child who cannot sustain oral feeding. ^[9]
4. Increasing the volume of standard formula raises the fluid load on a heart already in volume overload, worsening the tachypnoea, the sweating and the failure, and the tiring infant cannot take the larger volume anyway. Fortifying the feed to a higher calorie density delivers more energy in the same or a smaller volume, protecting the heart while raising the energy delivered. ^[9]
5. Untreated malnutrition in the cardiac infant raises the perioperative risk at surgical repair, impairs wound healing and immune defence, and slows the recovery after intervention. Nutrition is an outcome of congenital heart disease care because the infant who reaches surgery well grown has the better operative and developmental course, so the faltering centile is treated as a signal to act, not to wait. ^[9]