Enteral Feeding of Ketogenic Therapy

Use of an enteral feeding tube to provide all or part of a prescribed ketogenic dietary therapy is indicated in situations where oral intake is not possible due to medical conditions. It may also be used to supplement an inadequate oral intake resulting from physical or behavioural eating problems. A ketogenic enteral feed can be used for existing tube fed patients who are to be initiated on ketogenic dietary therapy, or for patients already established on ketogenic dietary therapy who subsequently require tube feeding. The most common feeding route is directly to the stomach via a naso-gastric tube (short term use, only) or a gastrostomy, through the abdominal wall (for longer term use), however it is also possible to feed directly into the duodenum or jejunum.

Prior to commencement of enteral feeding a full nutritional evaluation must be carried out by the dietitian; this will include assessment of current and past growth, current nutritional intake and route of feeding, bowel function, scope for inclusion of oral feeds and whether swallow has been adequately assessed by a speech and language therapist, and review of baseline ketogenic blood biochemistry results. Consideration of nutritional requirements will then enable the dietitian to calculate and advise on an appropriate ketogenic feeding regime.

Ketogenic feeds tend to be devised using the ketogenic ratio* system; a mathematical tool used to stabilise the fat, protein and carbohydrate proportions in Classical ketogenic diets.

*The ketogenic ratio is X÷Y

  • X = the number of grams of fat and
  • Y = the number of grams of [carbohydrate + protein combined]

Ketocal (Nutricia) is currently the only specialised ketogenic enteral feed range available on prescription in the UK and Ireland. Ketocal is available in a range of formulations with different age groups in mind; as a liquid formulation at 4:1 ratio (age>1year) and 2.5:1 ratio (for adolescents & adults) and as a powder formulation at 3:1 ratio (can be used from birth) and 4:1 ratio (age>1year).  They frequently require adjustment of the protein, fat or carbohydrate composition to match the individual ketogenic diet prescription and regular adjustment along the way based on growth, symptom changes and biochemical monitoring.

It is possible to devise alternative types of ketogenic enteral feeds using individual protein, fat and carbohydrate sources, with appropriate vitamin and mineral supplementation. This type of approach may be necessary if there are pre-existing food intolerances.

Transition from a normal enteral feed to a ketogenic feeding regime is generally achieved using a step-wise approach over a few days as tolerated: this can be implemented by either introducing the ketogenic feed as a percentage of the existing enteral feed, or introducing full ketogenic feeds at a reduced ketogenic ratio. Ketogenic enteral feeds can be given as separate units (bolus feeds) or via a pump over a longer time (continuous feeds), depending on the requirements of the individual and may need adjustments to the feed schedule to improve tolerance and optimise seizure control. Any feed given directly into the jejunum should always be delivered continuously.

Studies have shown that there is good efficacy and tolerability of ketogenic dietary therapy when provided by the enteral route (1, 2) with greater compliance over ketogenic meals. Calculating the prescription of a ketogenic enteral feed can be simpler for the dietitian and requires less education for families or patients. Due to ease of delivery ketosis can be easily achieved and errors are less common. However, where possible oral ability should not be compromised and regimes enabling a combination of enteral feeding and oral meals to suit the capacity and capabilities of the individual are a practical possibility too.

Possible side effects of ketogenic enteral feeding are similar to those seen with an oral diet; however particular consideration should be given to the risk of abdominal problems such as constipation and worsening of any pre-existing gastro-oesophageal reflux. The diet should be monitored in the same way as one taken orally. This will include home measuring of ketone levels in blood or urine, and regular clinic visits for assessment which will also include biochemical monitoring.

References

  1. Kossoff, E.H., McGrogan, J.R. & Freeman, J.M. (2004) Benefits of an all-liquid ketogenic diet. Epilepsia, 45, 1163.
  2. Hosain, S.A., La Vega-Talbott, M. & Solomon, G.E. (2005) Ketogenic diet in paediatric epilepsy patients with gastrostomy feeding. Paediatr Neurol, 32, 81-3.