Nutritional indices at admission are associated with mortality rates of patients in the intensive care unit

MIMIC-III (‘Medical Information Mart for Intensive Care’) is a large, single-center database comprising information relating to patients admitted to critical care units at a large tertiary care hospital. Data includes vital signs, medications, laboratory measurements, observations and notes charted by care providers, fluid balance, procedure codes, diagnostic codes, imaging reports, hospital length of stay, survival data, and more. The database supports applications including academic and industrial research, quality improvement initiatives, and higher education coursework.

Patients at risk of malnutrition and related morbidity and mortality can be identified with the Nutritional Risk Index (NRI). However, this index remains limited for elderly patients because of difficulties in establishing their normal weight. Therefore, we replaced the usual weight in this formula by ideal weight according to the Lorentz formula (WLo), creating a new index called the Geriatric Nutritional Risk Index (GNRI). First, a prospective study enrolled 181 hospitalized elderly patients. Nutritional status [albumin, prealbumin, and body mass index (BMI)] and GNRI were assessed. GNRI correlated with a severity score taking into account complications (bedsores or infections) and 6-mo mortality. Second, the GNRI was measured prospectively in 2474 patients admitted to a geriatric rehabilitation care unit over a 3-y period. The severity score correlated with albumin and GNRI but not with BMI or weight:WLo. Risk of mortality (odds ratio) and risk of complications were, respectively, 29 (95% CI: 5.2, 161.4) and 4.4 (95% CI: 1.3, 14.9) for major nutrition-related risk (GNRI: <82), 6.6 (95% CI: 1.3, 33.0), 4.9 (95% CI: 1.9, 12.5) for moderate nutrition-related risk (GNRI: 82 to <92), and 5.6 (95% CI: 1.2, 26.6) and 3.3 (95% CI: 1.4, 8.0) for a low nutrition-related risk (GNRI: 92 to < or =98). Accordingly, 12.2%, 31.4%, 29.4%, and 27.0% of the 2474 patients had major, moderate, low, and no nutrition-related risk, respectively. GNRI is a simple and accurate tool for predicting the risk of morbidity and mortality in hospitalized elderly patients and should be recorded systematically on admission.

Survivors of critical illness demonstrate skeletal muscle wasting with associated functional impairment. To perform a comprehensive prospective characterization of skeletal muscle wasting, defining the pathogenic roles of altered protein synthesis and breakdown. Sixty-three critically ill patients (59% male; mean age: 54.7 years [95% CI, 50.0-59.6 years]) with an Acute Physiology and Chronic Health Evaluation II score of 23.5 (95% CI, 21.9-25.2) were prospectively recruited within 24 hours following intensive care unit (ICU) admission from August 2009 to April 2011 at a university teaching and a community hospital in England. Patients were recruited if older than 18 years and were anticipated to be intubated for longer than 48 hours, to spend more than 7 days in critical care, and to survive ICU stay. Muscle loss was determined through serial ultrasound measurement of the rectus femoris cross-sectional area (CSA) on days 1, 3, 7, and 10. In a subset of patients, the fiber CSA area was quantified along with the ratio of protein to DNA on days 1 and 7. Histopathological analysis was performed. In addition, muscle protein synthesis, breakdown rates, and respective signaling pathways were characterized. There were significant reductions in the rectus femoris CSA observed at day 10 (−17.7% [95% CI, −25.9% to 8.1%]; P < .001). In the 28 patients assessed by all 3 measurement methods on days 1 and 7, the rectus femoris CSA decreased by 10.3% (95% CI, 6.1% to 14.5%), the fiber CSA by 17.5% (95% CI, 5.8% to 29.3%), and the ratio of protein to DNA by 29.5% (95% CI, 13.4% to 45.6%). Decrease in the rectus femoris CSA was greater in patients who experienced multiorgan failure by day 7 (−15.7%; 95% CI, −27.7% to 11.4%) compared with single organ failure (−3.0%; 95% CI, −5.3% to 2.1%) (P < .001), even by day 3 (−8.7% [95% CI, −59.3% to 50.6%] vs −1.8% [95% CI, −12.3% to 10.5%], respectively; P = .03). Myofiber necrosis occurred in 20 of 37 patients (54.1%). Protein synthesis measured by the muscle protein fractional synthetic rate was depressed in patients on day 1 (0.035%/hour; 95% CI, 0.023% to 0.047%/hour) compared with rates observed in fasted healthy controls (0.039%/hour; 95% CI, 0.029% to 0.048%/hour) (P = .57) and increased by day 7 (0.076% [95% CI, 0.032%-0.120%/hour]; P = .03) to rates associated with fed controls (0.065%/hour [95% CI, 0.049% to 0.080%/hour]; P = .30), independent of nutritional load. Leg protein breakdown remained elevated throughout the study (8.5 [95% CI, 4.7 to 12.3] to 10.6 [95% CI, 6.8 to 14.4] μmol of phenylalanine/min/ideal body weight × 100; P = .40). The pattern of intracellular signaling supported increased breakdown (n = 9, r = −0.83, P = .005) and decreased synthesis (n = 9, r = −0.69, P = .04). Among these critically ill patients, muscle wasting occurred early and rapidly during the first week of critical illness and was more severe among those with multiorgan failure compared with single organ failure. These findings may provide insights into skeletal muscle wasting in critical illness.