Enteral Feeding of Ketogenic Therapy

Use of an enteral feeding tube to provide all or part of a prescribed ketogenic 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 therapy, or for patients already established on ketogenic 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. At present there is one complete product available for ketogenic enteral feeding regimes. Ketocal (Nutricia) is available as a 4:1 or 3:1 ratio powder, or as a 4:1 ratio liquid. These formulations are based on the ratio system used in the classical ketogenic diet (fat: carbohydrate and protein) and are designed for use in children over 1 year. There are no ketogenic formulae designed for older children and adults available currently. The formulae readily 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 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; those who are able to eat should not be prevented from doing so simply for the above reasons. 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.