Effects of hypocaloric feeding on clinical outcome in ICU patients

Introduction

The risk of a severe malnutrition is particularly high in critically ill patients. On the other hand, to administer feeding overcoming the metabolic need should be considered a significant risk factor and not a useful approach in improving the outcome of ICU patients. To this purpose, a hypocaloric nutritional support has been proposed. It may satisfy the patient's caloric-proteic needs, and supply energy enough aimed to avoid the adverse effects of the stress-related metabolic response. The present study aimed to evaluate the nutritional support management in our ICU, and to assess the relative role of the enteral nutritional therapy on morbidity.

Methods

One hundred and fifty-one out of 194 adult patients admitted to our polyvalent ICU from 1 January 2005 to 30 September 2005 were retrospectively analyzed. Patients younger than 18 years, those requiring a length of stay less than 3 days, patients with an ideal body weight >30%, and those on parenteral nutritional therapy were excluded from the study. The enteral nutritional support contained 55% carbohydrates, 30% lipids and 15% proteins, and was administered by means of either a nasogastric or orogastric probe. The estimated total caloric need for each patient was calculated with the Harris-Benedict formula. The correction factor of 1.2 was used for patients admitted to the ICU after severe head injury. Multivariate and receiver-operating characteristic (ROC) curve analyses were applied.

Results

The daily average of theoretical kcals provided was 26.4 ± 6 kcals, with respect to 21.8 ± 3.4 kcals actually administered. Only 22% of patients received the amount of 90% of the theoretically calculated kcals. The ROC analysis identified a threshold of 70% for the theoretical/administered nutritional support ratio (T/A-NSR) value related to morbidity (the area under curve was 0.76; 95% CI = 0.681–0.843, P < 0.05). By using the threshold of 70% for the T/A-NSR value, we were able to split our patient population into two groups: group A, patients receiving a T/A-NSR value ≤ 70%, and group B receiving a T/A-NSR value >70%. The statistical analysis showed that morbidity, duration of mechanical ventilation, and ICU length of stay were higher in group A (P < 0.05).

Conclusion

Our findings showed that administering a lower nutritional support (i.e. hypocaloric nutritional support) than the theoretically calculated calories is associated with increased morbidity. However, hyponutrition should be considered not only a direct risk factor for morbidity, but a result of bad outcomes. In fact, gastrointestinal problems often occur in critically ill patients, and the enteral nutrition may not be sufficiently adequate. In such cases, the only alternative to enteral nutrition is total parenteral nutrition. In conclusion, proof that limiting the hyponutrition improves outcomes in this setting awaits a sound prospective goal-oriented trial investigating one or more strategies to improve the nutritional management of the critically ill patient.