Point-Counterpoint: Indirect Calorimetry Is not Necessary for Optimal Nutrition Therapy in Critical Illness

Comparison of predictive equations and indirect calorimetry in critical care: Does the accuracy differ by body mass index classification?

BACKGROUND

Nutrition support professionals are tasked with estimating energy requirements for critically ill patients. Estimating energy leads to suboptimal feeding practices and adverse outcomes. Indirect calorimetry (IC) is the gold standard for determining energy expenditure. However, access is limited, so clinicians must rely on predictive equations.

METHODS

A retrospective chart review of critically ill patients who underwent IC in 2019 was conducted. The Mifflin-St Jeor equation (MSJ), Penn State University equation (PSU), and weight-based nomograms were calculated using admission weights. Demographic, anthropometric, and IC data were extracted from the medical record. Data were stratified by body mass index (BMI) classifications, and relationships between estimated energy requirements and IC were compared.

RESULTS

Participants (N = 326) were included. Median age was 59.2 years, and BMI was 30.1. The MSJ and PSU were positively correlated with IC in all BMI classes (all P < 0.001). Median measured energy expenditure was 2004 kcal/day, which was 1.1-fold greater than PSU, 1.2-fold greater than MSJ, and 1.3-fold greater than weight-based nomograms (all P < 0.001).

CONCLUSION

Despite the significant relationships between measured and estimated energy requirements, the significant fold-differences suggest that using predictive equations leads to significant underfeeding, which may result in poor clinical outcomes. Clinicians should rely on IC when available, and increased training in the interpretation of IC is warranted. In the absence of IC, the use of admission weight in weight-based nomograms could serve as a surrogate, as these calculations provided the closest estimate to IC in participants with normal weight and overweight, but not obesity.

Indirect calorimetry: should it be part of routine care or only used in specific situations?

PURPOSE OF REVIEW

Indirect calorimetry (IC) is increasingly recommended to guide energy delivery in the ICU. This review aims to provide a critical overview of current literature in support of these recommendations.

RECENT FINDINGS

There is insufficient evidence to ascertain a mortality benefit from IC-guided energy delivery. However, large variations in energy expenditure during critical illness pose a risk for significant under- and overfeeding if IC is not routinely used.

SUMMARY

Even in the absence of demonstrable clinical benefits, there is a strong physiological rationale in favor of performing IC. Measurements can be prioritized in complex patients and should be repeated during prolonged ICU stay.

Association between caloric adequacy and short-term clinical outcomes in critically ill patients using a weight-based equation: Secondary analysis of a cluster-randomized controlled trial

Background

There is controversy over the optimal energy delivery in intensive care units (ICUs). In this study, we aimed to evaluate the association between different caloric adequacy assessed by a weight-based equation and short-term clinical outcomes in a cohort of critically ill patients.

Methods

This is a secondary analysis of a cluster-randomized controlled trial (N = 2,772). The energy requirement was estimated as 25 kcal/kg of body weight. The study subjects were divided into three groups according to their caloric adequacy as calculated by the mean energy delivered from days 3 to 7 of enrollment divided by the estimated energy requirements: (1) received &lt; 70% of energy requirement (hypocaloric), (2) received 70–100% of energy requirement (normocaloric), and (3) received &gt; 100% of energy requirement (hypercaloric). Cox proportional hazards models were used to analyze the association between caloric adequacy and 28-day mortality and time to discharge alive from the ICU.

Results

A total of 1,694 patients were included. Compared with normocaloric feeding, hypocaloric feeding significantly increased the risk of 28-day mortality (hazard ratio [HR] = 1.590, 95% confidence interval [CI]: 1.162–2.176, p = 0.004), while hypercaloric feeding did not. After controlling for potential confounders, the association remained valid (adjusted HR = 1.596, 95% CI: 1.150–2.215, p = 0.005). The caloric adequacy was not associated with time to discharge alive from the ICU in the unadjusted and the adjusted models.

Conclusion

Energy delivery below 70% of the estimated energy requirement during days 3–7 of critical illness is associated with 28-day mortality.

Clinical trial registration

[https://www.isrctn.com/ISRCTN12233792], identifier [ISRCTN12233792].

Nutrition Therapy in Non-intubated Patients with Acute Respiratory Failure

PURPOSE OF REVIEW

A challenging aspect of the care for patients with acute respiratory failure is their nutrition management. This manuscript consists of a literature review on nutrition therapy in non-intubated patients with acute respiratory failure receiving high-flow nasal cannula oxygenation or non-invasive positive pressure ventilation.

RECENT FINDINGS

Studies show that non-intubated patients with acute respiratory failure either on non-invasive ventilation or high-flow nasal cannula are largely underfed in the initial phase of their hospitalization. Although data is limited, the available evidence suggests the feasibility of initiating oral diet in the majority of these patients in the early phase. Initial evaluation includes mental status evaluation, the Yale swallowing screening protocol, and an assessment of severity of illness. The goal should be to initiate oral diet within 24 h. If patient cannot initiate oral diet, the reason for not initiating oral diet should dictate the next step. For instance, if the reason is failure of the swallow screening, further evaluation with fiberoptic endoscopy is warranted. The inability to provide oral diet for a patient in respiratory distress may a harbinger of failure of non-invasive oxygen therapy and should prompt consideration for endotracheal intubation. We suggest placement of a small-bore feeding tube for enteral nutrition if patient is unable receive oral diet after 48 h.

CONCLUSIONS

The nutrition management of these patients is better provided by a multidisciplinary team in a protocolized manner.