Leptin, IGF1 and the Refeeding Index

Background and study hypothesis: Refeeding syndrome is a dangerous condition which could arise if patients who have had little or no food for many days, are started on any form of feeding. The metabolic consequences of this condition could affect the heart, lungs and nervous system of the patient and cause serious imbalance in the level of salts in the body. The available guidelines for predicting that refeeding syndrome may occur are very subjective since they depend mainly on a history which is sometimes difficult to obtain from the patient. The main biochemical landmark that refeeding syndrome has occurred is a fall in the phosphate levels once feeding has been started. There are currently no biochemical markers that can identify patients at risk of developing refeeding syndrome. Leptin and IGF1 are hormones which have been observed to go down if someone has had little or no food for a while. The investigators therefore hypothesized that using a combination of leptin and IGF1 values in a 'Refeeding Index' would make the latter a useful biochemical marker to predict that refeeding may occur, hence take the precautionary measures to avoid its occurrence before starting feeding. Design: Thirty five consecutive patients referred for commencement of parenteral nutrition (PN) were included. Serum leptin and IGF1 were measured prior to starting PN. Electrolytes, liver and renal function tests were measured before and daily for one week after initiating PN. The primary outcome was a decrease in phosphate on day two or three after initiating PN. A 'Refeeding Index' (RI) was defined as leptin x IGF1 divided by 2800 to produce a ratio of 1.0 in patients who are well nourished.