Limited evidence suggest that assessment of muscle mass, indirect calorimetry, and careful monitoring of urea level may help guide nutrition therapy in older patients in the intensive care unit (ICU), according to a Singapore study. Other recommendations for general ICU patients may be used for those with sound clinical discretion.
“There were only five randomized controlled trials (RCTs) for two topics: route or timing of nutrition therapy and pharmaconutrition,” the researchers said. “In contrast, among general critically ill patients … there were already 207 RCTs with 23,091 patients across 34 topics.” [J Parenter Enteral Nutr 2010;34:697-706]
The databases of Medline and Embase were searched through 9 February 2022 for studies on critically ill patients aged ≥60 years assessing any area of nutrition therapy. The researchers did not apply any study design or language restrictions.
Thirty-two studies including five RCTs met the eligibility criteria. Six topics were identified, as follows: (1) nutrition screening and assessments, (2) muscle mass assessment, (3) route or timing of nutrition therapy, (4) determination of energy and protein requirements, (5) energy and protein intake, and (6) pharmaconutrition. [Ann Acad Med Singap 2022;51:629-636]
Similar findings were noted for topics 1, 3, and 6 among general adult ICU patients. Skeletal muscle mass at ICU admission was markedly lower in older than younger patients. Low muscularity at ICU admission elevated the risk of adverse outcomes in older critically ill patients.
“Skeletal muscle is the most abundant tissue and the main reservoir of amino acids for vital organs during the stressed state,” the researchers said. [Am J Clin Nutr 1992;56:19-28;
Calcif Tissue Int 2015;96:183-195]
“The direct measurements of muscle mass using imaging procedures such as computed tomography and ultrasound at ICU admission may more precisely reflect patients’ nutritional status,” they added. [Clin Nutr 2022;41:1425-1433]
Energy, protein requirements
Based on weight-based equations, predicted energy requirements significantly strayed from indirect calorimetry measurements in older patients compared to their younger counterparts. In addition, older ICU patients needed higher protein intake (>1.5 g/kg/day) to achieve nitrogen balance, but they run the risk of developing azotaemia at similar protein intake.
“Overall, the optimal energy and protein dose for older critically ill patients are yet to be determined,” the researchers said.
“Physiologic data suggest that older patients require higher protein intake than younger patients; however, caution needs to be exercised with higher protein as older patients are at a higher risk of azotaemia than younger patients at similar protein intake,” they added. [J Parenter Enteral Nutr 2015;39:282-290; J Parenter Enteral Nutr 2022;46:75-82]
To guide nutrition intervention, the American Society for Parenteral and Enteral Nutrition 2016 guidelines recommended using Nutrition Risk Screening 2002 (NRS-2002) and an ICU-specific nutrition score (modified nutrition risk in critically ill [mNUTRIC]). Of note, only the latter was developed and validated among ICU patients. [Crit care 2011;15:R268;
Clin Nutr 2016;35:158-162]
“Similar to general adult critically ill patients, current evidence suggests that mNUTRIC and Subjective Global Assessment may be the best available tools to aid prognostication of clinical outcomes in older critically ill patients,” the researchers said. “High-quality RCTs are needed to determine whether these tools can identify patients who may benefit from higher nutrition delivery.”