A practical guide to the introduction and use of comida-PKU A formula

1.0 Overview of feeding an infant with PKU.

1.1 Nutrition prescription using comida-PKU A formula at diagnosis.

1.2 Example feeding plans.

1.3 Check list for blood monitoring.

1.4 Fine-tuning the nutrition prescription.

2.0 Practical feeding strategies to use with caregivers.

2.1 Practical points for effective communication between HCPs and caregivers.

3.0 References

Newly diagnosed infants with PKU are prescribed a phe-free formula (comida-PKU A formula) immediately after diagnosis is confirmed. Feeding an infant with PKU is a balance between providing phe-free formula alongside adequate amounts of phe from HM/SIF with the goal of keeping phe levels in target therapeutic range (120-360 µmol/L)^{1, 2}. This balance can be achieved with HM or SIF as the source of phe, and a family should be supported in making the appropriate choice for their family and their infant, with relevant healthcare professionals’ input as appropriate. 

comida-PKU A formula may be used from diagnosis in combination with HM/SIF or as a sole source of nutrition for a brief period known as a “washout” in order to achieve a rapid reduction in blood phe levels.

Healthcare providers should support a family’s decision to BF or provide HM as the intact protein source for an infant with PKU. 

comida-PKU A formula combined with bottle-fed HM or feeding at the breast is able to maintain satisfactory blood phe control provided there is adequate HM available for the infant and blood phe levels can be closely monitored³. HM offers nutritional benefits including higher long chain polyunsaturated fatty acid concentrations and a lower phe content, 47 mg/100 ml in HM3 compared with approximately 56 mg/100 ml in SIF³. 

Breastfeeding an infant with PKU is based on the principle of giving a measured volume of comida-PKU A formula to offset the infant’s appetite for breastfeeds. Feeding a measured amount of comida-PKU A formula alongside each breastfeed, or alternating measured feeds of comida-PKU A formula with breastfeeds, decreases the total amount of HM consumed and therefore decreases total phe intake. Infants can still feed on demand, varying the quantity of feeds from day to day provided that the prescribed quantity of comida-PKU A formula is given throughout the day3. Successful PKU management with breastfeeding is achieved via close monitoring of blood phe levels and adjustment of the prescribed volume of comida-PKU A formula by the metabolic healthcare professional in order to maintain blood phe control.

There are various options for feeding an infant with SIF and comida-PKU A formula. With the help of healthcare providers, including the metabolic  healthcare professional, families may choose a SIF supplemented with DHA and ARA that is best for their infant and family circumstances. 

SIF and comida-PKU A formula may be given in separate or mixed bottles, with a variety of feeding approaches capable of optimizing blood phe control and catering to a family’s individual circumstances.

Blood phe levels are used to determine whether the volume of comida-PKU A formula and HM/SIF should be adjusted. Expect to adjust the feeding plan weekly, especially during the first two months of life. Blood phe levels should be checked at least weekly throughout infancy^{1, 3}.

The quantity of phe tolerated by infants will vary and be guided by blood phe levels. Individual phe tolerance will vary significantly throughout infancy with changes in growth and development. It is vital to investigate the possible causes for changes in phe level before adjusting the feeding plan. Consider waiting for two consecutive blood phe levels to indicate the need for a feeding plan adjustment, unless the blood phe level is very low or very high.

comida-PKU A formula and HM/SIF may continue to provide 100% of the infant’s nutrition requirements until the age of 6 months, or when the infant is developmentally ready for the introduction of solids.

Monitor blood phe levels weekly or more frequently as needed to achieve stability in blood phe treatment range (120-360 umol/L)^2-3.

• comida-PKU A formula and phe source should be given together at each feed, or at alternating feeds to ensure nutrient availability throughout the day.
• If the prescribed volume of comida-PKU A formula is not taken, it may cause a rise in blood phe levels.
• Blood phe levels are used to determine whether comida-PKU A formula, SIF/HM prescription should be adjusted.
• The infant should be weighed at each clinic visit.

If a washout period is not required or reintroducing intact protein source, the following feeding plans illustrate 2 methods for calculating the feeding plan whether breast feeding or bottle feeding with expressed HM or SIF.

Example using a 6-day old infant diagnosed with PKU, weight 3.5 kg.

Using precise feeding volumes
comida-PKU A formula & BF	comida-PKU A formula & expressed HM/SIF
Estimate total volume intake per day using 150 ml/kg3, 4 = 525 ml/day (or use infant’s usual total volume intake if known).
Estimated phe need = 130-430 mg/day³. Using 150 mg phe/day as an example:
Estimate amount of HM needed:  ~320 ml HM (47 mg phe/100 ml) HM will not actually be measured but this estimate  gives a place to start.	Estimate amount of HM/SIF needed:  ~320 ml HM (47 mg phe/100 ml)  ~250 ml SIF (60 mg phe/100 ml)
Estimate amount of comida-PKU A formula needed to meet remaining fluid needs.
525 ml total volume – 320 ml HM = 205 ml comida-PKU A formula per day.	525 ml total volume – 320 ml HM = 205 ml comida-PKU A formula per day 525 ml total volume – 250 ml SIF = 275 ml comida-PKU A formula per day.
Divide total amount of estimated comida-PKU A formula needed by number of feeds per day. 205 ml comida-PKU A formula / 8 feeds per day = 25 ml comida-PKU A formula per feed Feed 25 ml comida-PKU A formula prior to each breastfeed and then allow baby to feed at breast to appetite. OR Alternate feeds of 50 ml comida-PKU A formula with BF.	Establish mixing prescription per bottle by dividing HF/SIF and comida-PKU A formula needed per bottle* If using HM: 320 ml HM + 205 ml comida-PKU A formula per day / 8 feeds per day = 40 ml HM + 25 ml comida-PKU A formula per feed If using SIF: 250 ml SIF + 275 ml comida-PKU A formula / 8 feeds per day = 30 ml SIF + 35 ml comida-PKU A formula per feed.
As a starting point, try to simplify the above plans into more easily measurable quantities such as:
30 ml (1 fl oz) comida-PKU A formula prior to each BF. OR Alternate 60 ml (2 fl oz) comida-PKU A formula with BF.	30 ml (1 fl oz) SIF OR 45 ml (1.5 fl oz) HM + 30 ml (1 fl oz) comida-PKU A formula per feed.

_{* Infants should be fed to appetite when hungry and total liquid volume per day should not be limited to establish phe level control. If the estimated volume intake does not satisfy the infant, then additional feeds of comida-PKU A formula alone can be given or in some cases additional comida-PKU A formula + HM/SIF may indicated.}

Using feeding volume percentages
comida-PKU A formula & BF	comida-PKU A formula & expressed HM/SIF
Estimate total volume intake per day using 150 ml/kg3, 4 = 525 ml/day (or use infant’s usual total volume intake if known).
Establish appropriate percentage of intake needed from comida-PKU A formula and intact protein source. Consider starting with a 50/50% prescription until individual phe tolerance is better understood.
525 ml per day x 50% = 260 ml/day comida-PKU A formula + 260 ml/day HM (HM is not actually measured, but this is just a place to start) Divide estimated comida-PKU A formula volume among number of feeds per day.  260 ml comida-PKU A formula / 8 feeds per day = ~30 ml comida-PKU A formula per feed Feed 30 ml (1 fl oz) comida-PKU A formula prior to each BF and then allow infant to feed at breast to appetite.  OR Alternate feeds of 60 ml (2 fl oz) comida-PKU A formula with breastfeeds.	525 ml per day x 50% = 260 ml/day comida-PKU A formula + 260 ml/day HM OR SIF Establish mixing prescription per bottle by dividing HM/SIF and comida-PKU A formula needed per bottle 35 ml SIF/HM + 35 ml comida-PKU A formula to make a 70 ml bottle* Consider simplifying the above into more easily measurable quantities such as:  30 ml (1 fl oz) SIF/HM + 30 ml (1 fl oz) comida-PKU A formula per feed

_{* Infants should be fed to appetite when hungry and total liquid volume per day should not be limited to establish phe level control. If the estimated volume intake does not satisfy the infant, then additional feeds of comida-PKU A formula alone can be given or in some cases additional comida-PKU A formula + HM/SIF may indicated.}

Many factors can affect blood phe levels. Always check for causes of high or low blood phe level before making a change to the nutrition prescription.

Many factors can affect blood phe levels. Always check for causes of high or low blood phe level before making a change to the nutrition prescription.

For all infants, frequent monitoring of phe levels is key, but try not to make changes to a feeding plan too frequently.

Consider:

• Many factors affect phe levels; review all causes in this section
• Monitor phe level trends
  • Unless phe level is very low or very high consider:
  • Continuation of the current plan
• Monitoring 2 consecutive phe levels before adjusting prescription
• In general, do not make more than 1 change to the plan in 1 week

For phe levels that ARE very low or very high:

• Consider repeating blood phe level sooner than 1 week to guide interventions.

* Although a 50% increase seems high, it often coincides with a simultaneous increase in total infant feeding volume per day.

Feeding bottles with necessary measurement markings (demarcation) for infant's recipe.

• Appropriately staged nipples for infant feeding
• Adequate supply of comida-PKU A formula
• HM pump and supplies if needed to express
• Adequate supply of SIF (if using)

• Use comida-PKU A formula scoop (or gram scale) to mix comida-PKU A formula. Do not use scoops from other formula containers to mix comida-PKU A formula
• Ensure family has access to a safe water source for formula mixing

• Inquire about the most effective written method for family to receive new recipes and mixing instructions.

  Review mixing at every visit

  Confirm family/caregivers are able to procure more comida-PKU A formula and SIF (if using) when supplies are low. Consider providing written guidance on where families can obtain these formulas. Direct families to appropriate agencies and services if needed to obtain SIF at low-cost or for free.