Nitrogen balance and outcomes in critically ill patients: A systematic review and meta-analysis

Abstract

ObjectiveNitrogen balance (NB) is a commonly used nutrition indicator in clinical practice, while its relation to the interpretation of protein malnutrition and outcomes in critically ill patients remains unclear. This study aimed to evaluate the impact of NB on prognosis in such a patient population.MethodsWe searched for relevant studies in PubMed, EMBASE, and the Cochrane Database up to May 10, 2022. Meta-analyses were performed to evaluate the relationship between NB (initial, final, or absolute change of NB levels) and prognosis and important clinical outcomes in critically ill patients. Pooled odds ratios (ORs) and mean differences (MDs) together with their 95% confidence intervals (CIs) were calculated. We also conducted subgroup analyses to explore the sources of heterogeneity.ResultsEight studies with 1,409 patients were eligible. These studies were moderate to high quality. When pooled, the initial NB was comparable between the survival and non-survival groups (five studies, MD 1.20, 95% CI, −0.70 to 3.11, I2 = 77%; P = 0.22), while a significantly higher final NB in the survival group than that in the death group (two studies, MD 3.69, 95% CI, 1.92–5.46, I2 = 55%; P < 0.0001). Two studies provided the absolute change of NB over time and suggested survival patients had more increased NB (MD 4.16 g/day, 95% CI, 3.70–4.61, I2 = 0%; P < 0.00001). Similarly, for studies utilizing multivariate logistic regression, we found an improved NB (four studies, OR 0.85, 95% CI, 0.73–0.99, I2 = 61%; P = 0.04) but not an initial NB (two studies, OR 0.92, 95% CI 0.78–1.08, I2 = 55%; P = 0.31) was significantly associated the risk of all-cause mortality. These results were further confirmed in subgroup analyses. In addition, patients with improved NB had more protein and calorie intake and a similar length of stay in hospital than those without.ConclusionsOur results suggested that an improved NB but not the initial NB level was associated with all-cause mortality in critically ill patients. This highlights the requirement for dynamic monitoring of NB during nutrition treatment. Further randomized clinical trials examining the impact of NB-guided protein intake on clinical outcomes in critically ill patients are warranted.Systematic review registrationINPLASY202250134, https://doi.org/10.37766/inplasy2022.5.0134.

Analysis of Nitrogen Balance Test in Patients With Traumatic Brain Injury

“…When this catabolic phase is severe, many patients tend to have a poor prognosis [3][4][5][6][7][8][9] . This trend applies to critically ill and neurological critically ill pa-tients 10) . Neurological critically ill patients also have higher morbidity and mortality if insufficient nutrient supply is poor [11][12][13] .…”

High protein intake and nitrogen balance in patients receiving venovenous extracorporeal membrane oxygenation: A descriptive cohort study

“…9,10 Recent research suggests a direct relationship between negative nitrogen balance (NB) and mortality in critically ill patients, particularly later during critical care; however, the influence of NB results in patients receiving VV ECMO continues to require exploration. 8,11 The range used to estimate protein needs was increased based on published findings. 9,10 The primary aim of this retrospective, observational study was to describe the ability of higher protein nutrition support regimens to achieve nitrogen equilibrium in critically ill adults receiving VV ECMO defined by NB.…”

“…Catabolism of lean mass is increased following the mobilization of stress metabolism to support these needs. Increased protein administration may be able to blunt nitrogenous losses; however, significant attenuation of catabolism may not be possible until resolution of the stress response is achieved 8 . Patients receiving VV ECMO may have higher inflammatory responses due to ECMO‐specific factors as well as considerations related to acute respiratory distress syndrome (ARDS).…”

“…Previously, work from our institution found that patients with and without obesity receiving VV ECMO required more protein than the recommendation for general critical illness to avoid negative nitrogen equilibrium due to increased catabolic losses 9,10 . Recent research suggests a direct relationship between negative nitrogen balance (NB) and mortality in critically ill patients, particularly later during critical care; however, the influence of NB results in patients receiving VV ECMO continues to require exploration 8,11 . The range used to estimate protein needs was increased based on published findings 9,10 .…”