The Bioelectrical Impedance Analysis and Muscular Ultrasound in the Detection of Nutritional Status in Critically Ill Patients: The BUS Study

the Bioelectrical impedance analysis and muscular Ultrasound in the detection of nutritional Status in critically ill patients

Critically ill patients are characterized by wide variations in their carbohydrate, lipid, and protein metabolism. Such variations can lead to increase in their energy requirement with accelerated protein catabolism and ultimately alterations of their immune and gastrointestinal systems, and in a variable frame time, it lead to a disruption of muscular function that increased the ICU and hospital stay and mortality. It has been observed that most of the critically ill patients who survive acute respiratory distress syndrome have to deal with a wide variety of consequences, including muscular wasting and weakness, and these conditions could last for at least one year. Intensive care unit acquired weakness has been defined as generalized weakness that develops during critical illness and where no other explanation than critical illness is present and is associated with long-term consequences from the medical, human, and socioeconomic point of view. In the normal weight person, the metabolic response to injury causes an increase in protein and energy requirements. As a result, endogenous substrates serve as fuel sources and as precursors for protein synthesis. From the nutrition perspective, one of the main challenges of providing nutritional support to critically ill patients is to stop or slow lean mass losses. For these reasons, it is fundamental for the nutritional support clinician to be able to measure and assess muscle wasting during critical illness, using an easy and accessible technique.

There are multiple methods to conduct these measurements. Usually, admission weight and height should be used to calculate the ideal body weight (IBW), the percentage of IBW, and the Body Mass Index (BMI). However, the accuracy of these measures could be very scares. Skeletal muscle wasting in the critically ill is often masked by fluid retention. In these circumstances the normal anthropometric methods of assessing changes in body mass and composition are not applicable, as the techniques all assume a normal state of hydration. Thus, additional anthropometric data although useful in ambulatory patients, are not as accurate measures of malnutrition in the critically ill patients. Moreover, some serum proteins (such as albumin level and several other transport proteins) are commonly measured as surrogates of visceral protein status. However, all of them are influenced by many factors such as synthesis and degradation rates and vascular losses into the surrounding interstitium, in addition to losses through the gut or kidney. As a result, their levels drop by inflammation or sepsis where high levels of interleukin-6 stimulate acute phase protein production as it inhibits transport protein production. Thus, they are a poor indicator of critically ill patients' nutritional status as they serve as a marker of injury and metabolic response to stress. For these reasons, in the last few decades, several different tools have been developed to integrate the clinical and biochemical nutritional evaluations. Among these, the bioimpedance analysis (BIA) and the muscular ultrasonography (MU) seem to be promising tools for this purpose.

The aim of this project is to compare and integrate the data collected by BIA and MU and the routinely clinical used parameters of nutrition to define the nutritional status of critically ill patients. The data from these tools and the biochemical and anthropometric nutritional data (including the nutritional support) will be collected at the admission in ICU and followed up within the first week of ICU stay.

Bioimpedance analysis