520 Are Predicted Protein Recommendation Adequate When Unable to Utilize Nitrogen Balance Testing?

TL;DR

This study compares predicted protein needs with measured values in burn patients and finds predicted amounts may be too high.

Contribution

The study evaluates the accuracy of protein requirement estimates using indirect calorimetry versus urine urea nitrogen balance in burn patients.

Findings

Predicted protein needs (25% of IC) were higher than observed UUN-based requirements by 41g on average.

Poor correlation (Pearson's coefficient 0.06) was found between predicted and observed protein needs.

Larger studies are needed to improve accuracy of estimated protein requirements for burn patients.

Abstract

Evidence based practice on providing adequate protein for burn patients is limited. Recommendations range from 20-25% of overall caloric needs deriving from protein, or 1.5 – 4 grams (g) per kilogram (kg) of body weight. Our American Burn Association (ABA) verified burn center uses both indirect calorimetry (IC) and urine urea nitrogen balance (UUN) as a guide for patient specific caloric and protein needs. The objective of this study was to evaluate protein requirements based on 25% of predicted IC caloric needs compared to urine UUN.

This was a single center retrospective analysis at an ABA verified burn center. We included patients with 10% or greater total body surface area (TBSA) burns between 3/15/23 and 9/1/23 who completed an IC and a UUN. We excluded occurrences of invalid IC results, inaccurate protein intake records, or if a UUN occurred >7 days from the IC. Expected (Exp) protein requirements were calculated by 25% of IC resting energy expenditure multiplied by 1.3 activity factor. Observed (Obs) protein requirements were calculated by a collected 12-hour UUN + 4 grams for a ne positive nitrogen balance. Correlation of Exp vs Obs protein and matched mean difference with an assessment of estimate bias was conducted overall and as subgroups based on TBSA 10-19.9 and 20% or greater.

After excluding 28 incomplete assessment pairs, 15 patients representing 34 IC and UUN assessments (8 with >1 assessment) were included. Median age and TBSA were 31 years (30, 52.5) and 20% (13.6, 33.1), respectively. Total cohort Exp and Obs protein requirements were 198 and 157 g (matched mean difference 41 g, p< 0.001), and did not correlate (Pearsons coefficient 0.06, p=0.73). In those 20% TBSA or greater, 8 patients (median TBSA 31.1%; 21.7, 59) had 23 assessments. Exp vs Obs protein requirements were 205 and 160 g (matched mean difference 45 g, p=0.001) and, poorly correlated (Pearsons coefficient 0.11, p=0.62). In those 10-19.9% TBSA, 7 patients (median TBSA 12.75%; 10.8, 14.75) had 11 assessments. Exp vs Obs protein requirements were 184.5 and 150.5 g (matched mean difference 34 g, p=0.073) and, weakly correlated (Pearsons coefficient 0.22, p=0.51).

Calculating protein demands based on 25% of IC caloric requirements may overestimate protein needs when compared to a measured UUN. Larger studies and continued research in nutrition support are needed to improve accuracy of estimated protein requirements.

In patients with large burns (>10% TBSA), burn centers should consider using UUN to more accurately determine patients’ adequate protein needs.