Comparison of mNUTRIC score and ultrasound measured upper arm muscle mass as a predictor of 28-day mortality in patients with gastrointestinal surgeries - A prospective cohort study

Nutrition plays a major role in the recovery of patients; mainly in the post operative period. In patients admitted to the Intensive Care Unit (ICU) there is a high chance of malnourishment characterized by prolonged mechanical ventilation and ICU stay with increased morbidity and mortality[1]. Patients who have undergone gastrointestinal surgeries are prone to malnourishment during postoperative period due to alteration in gastric structure and ability to absorb nutrients. [2] There are many guidelines for nutritional assessment which include the American Society for Parenteral and Enteral Nutrition (ASPEN), the Society for Critical Care Medicine, and the European Society for Clinical Nutrition and Metabolism (ESPEN), suggesting early nutritional intervention for patients admitted to a surgical intensive care unit (SICU) [3]. However, studies have reported significant gaps between guidelines and commonly observed practices in surgical patients in intensive care units (ICUs) [4]. In 2011, Heyland et al. [5] developed the Nutrition Risk in the Critically Ill (NUTRIC) score mainly to benefit the patients who have undergone gastrointestinal surgeries. The NUTRIC score has 6 components: Age, Acute Physiology and Chronic Health Evaluation II, Sequential Organ Failure Assessment score, Number of comorbidities, Days from hospital admission to ICU admission, and Serum Interleukin 6 (IL-6). Since IL-6 cannot be assessed on a daily basis the NUTRIC score without serum IL-6 (modified NUTRIC score) was developed by Rahman et al in 2015[6]. Malnutrition is also related to the lean body mass. But the abovementioned scores do not rely upon anthropometry. There are drawbacks using these anthropometric measurements which includes alterations caused by the fluid overload and inflammatory process in critically ill-patients [7]. Such discrepancies led to a need for an easy to perform, accessible technique to assess nutritional status in critically ill patients which is independent of the information given by the patient or caregivers. For this reason, imaging technique has been listed as an important tool in the assessment of lean body mass in postoperative patients amongst which computed tomography (CT SCAN) is the gold standard technique. This technique has major limitations which includes cost, shifting of patients to specific area, expert personnel for study and so on which has made it unreliable as a component for nutritional assessment [8,9]. Hence, CT scan is not a suitable tool for the daily practice [10].  A technique which overcomes these drawbacks would be Ultrasound, an accessible tool in postoperative areas [11]. Various studies have been done on monitoring muscle mass using ultrasound which plays a role in critical care [13]. Studies have been done to establish relationship between mortality and muscle mass measured by ultrasound independently of illness severity [12]. The forementioned study used rectus femoris (RF) and vastus intermedius muscle mass measured at bedside [12]. The use of ultrasound is operator dependent and comes with a disadvantage of interobserver errors. An Indian study has been done to assess the intra and interobserver errors of arm muscle thickness measured by ultrasound in critical care [14]. This study was based on high ICC (Intraclass Correlation Co Efficient Factor) for both intra- and inter-observer measurement of flexor muscle thickness of the arm. The results imply that USG may be used as an objective and reliable tool for the assessment of thickness of flexor muscle of the arm by critical care physicians. Hence, we decided to use upper arm muscle which is also the most accessible muscle mass as a standard measurement in the study[13].