Application of Prophylactic Low Calorie Feeding in Critically Ill Patients With High-risk Refeeding Syndrome

Critically ill patients with high-risk nutrition are often at risk of refeeding syndrome(RFS), that the incidence of RFS is as high as 30-50%. It is sure that patients with refeeding syndrome were treated with restrictive enteral nutrition, but the definition of refeeding syndrome is not uniform, and there is still a lack of awareness high-risk patients of RFS to receiving early empirical low-calorie feeding intervention. So, we designed the study which is divided into three stages. Firstly, the monitoring rate of RFS was reviewed to evaluate the incidence of RFS in general ICU. Secondly, the best diagnostic criteria of RFS were prospectively defined. Finally, on this basis, it is assessed whether early low-calorie feeding could improve prognosis in high-risk patients with RFS.

Stage 1: the monitoring rate of re-feeding syndrome in our department was reviewed to evaluate the incidence of re-feeding syndrome in severe patients,which is not described in detail; Stage 2:This part is a prospective observational study，divided into two group,that is, RFS group(their serum phosphate concentration decreased to below 0.87 mmol/L within 72 h after starting nutritional support and the biological variation needed to be greater than 30% decrease from any concentration previously recorded), which is divided into three sub-group(Group 1 that a drop of \>0.16 mmol/L from any previous measurement, to below 0.65 mmol/L within 72 h after starting nutritional support, Group 2 that their serum phosphate concentration decreased to below 0.87 mmol/L within 72 h after starting nutritional support and the biological variation needed to be greater than 30% decrease from any concentration previously recorded, and Group 3 that their serum phosphate concentration decreased to below 0•32 mmol/L within 72 h after starting nutritional support.), and nRFS group(non-RFS that the serum phosphate do not up to the criteria). And the RFS group will be receiving the low-calorie feeding intervention, the nRFS group will be receiving the standard feeding according to the ASPEN guideline of 2016.

Stage 3: On this basis of stage 2, it is assessed whether early low-calorie feeding could improve prognosis in high-risk patients with RFS who was defined in NICE(National institute for the health and care excellence).The part of stage 3, divided into two groups that standard calorie feeding group and low calorie feeding group, aims to assess whether early low-calorie feeding could improve prognosis in high-risk patients with RFS.

Eligibility Criteria:
Inclusion Criteria:

* Critically ill patients at least 18 years old;
* No history of enteral nutrition or parenteral nutrition within 1 week before ICU admission or ICU admission within 1 week;
* Mechanical ventilation patients requiring enteral nutrition support for \>72h

Exclusion Criteria:

* refuse to join this study;
* enteral nutrition support for less than 3 days or have enteral nutrition contraindication;
* less than 18 years old;
* artificial nutrition (enteral/parenteral nutrition) has been applied to patients before admission;
* other factors of hypophosphatemia: continuous hemodialysis, recent parathyroidectomy, or hyperphosphatemia after treatment;